Add include guards and header comments to sources

222 files changed, 1641 insertions, 39 deletions

diff --git a/src/core/config/boolean.cc b/src/core/config/boolean.cc
index 45d5a38..74c7b07 100644
--- a/src/core/config/boolean.cc
+++ b/src/core/config/boolean.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: boolean.cc
+// Description: Boolean config value
+
 #include "core/pch.hh"
 
 #include "core/config/boolean.hh"
diff --git a/src/core/config/boolean.hh b/src/core/config/boolean.hh
index cfd8b0b..238b978 100644
--- a/src/core/config/boolean.hh
+++ b/src/core/config/boolean.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: boolean.hh
+// Description: Boolean config value
+
+#ifndef CORE_CONFIG_BOOLEAN_HH
+#define CORE_CONFIG_BOOLEAN_HH
 #pragma once
 
 #include "core/config/ivalue.hh"
@@ -23,3 +30,5 @@ public:
     static bool from_string(std::string_view value);
 };
 } // namespace config
+
+#endif
diff --git a/src/core/config/ivalue.hh b/src/core/config/ivalue.hh
index 13e9a3a..088276a 100644
--- a/src/core/config/ivalue.hh
+++ b/src/core/config/ivalue.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: ivalue.hh
+// Description: Base config value interface
+
+#ifndef CORE_CONFIG_IVALUE_HH
+#define CORE_CONFIG_IVALUE_HH
 #pragma once
 
 namespace config
@@ -9,3 +16,5 @@ public:
     virtual std::string_view get(void) const = 0;
 };
 } // namespace config
+
+#endif
diff --git a/src/core/config/number.hh b/src/core/config/number.hh
index 4f185e1..eb1f462 100644
--- a/src/core/config/number.hh
+++ b/src/core/config/number.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: number.hh
+// Description: Arithmetic config value
+
+#ifndef CORE_CONFIG_NUMBER_HH
+#define CORE_CONFIG_NUMBER_HH
 #pragma once
 
 #include "core/config/ivalue.hh"
@@ -128,3 +135,5 @@ inline void config::Number<T>::set_limits(T min_value, T max_value)
     m_value = std::clamp(m_value, m_min_value, m_max_value);
     m_string = std::to_string(m_value);
 }
+
+#endif
diff --git a/src/core/config/string.cc b/src/core/config/string.cc
index 198b448..e5820f6 100644
--- a/src/core/config/string.cc
+++ b/src/core/config/string.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: string.cc
+// Description: String config value
+
 #include "core/pch.hh"
 
 #include "core/config/string.hh"
diff --git a/src/core/config/string.hh b/src/core/config/string.hh
index 8fd3901..faecb67 100644
--- a/src/core/config/string.hh
+++ b/src/core/config/string.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: string.hh
+// Description: String config value
+
+#ifndef CORE_CONFIG_STRING_HH
+#define CORE_CONFIG_STRING_HH
 #pragma once
 
 #include "core/config/ivalue.hh"
@@ -29,3 +36,5 @@ constexpr const char* config::String::c_str(void) const noexcept
 {
     return m_value.c_str();
 }
+
+#endif
diff --git a/src/core/io/buffer.cc b/src/core/io/buffer.cc
index d0fda49..dffd9bc 100644
--- a/src/core/io/buffer.cc
+++ b/src/core/io/buffer.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: buffer.cc
+// Description: QDataStream-esque buffer
+
 #include "core/pch.hh"
 
 #include "core/io/buffer.hh"
diff --git a/src/core/io/buffer.hh b/src/core/io/buffer.hh
index 450a86f..100a933 100644
--- a/src/core/io/buffer.hh
+++ b/src/core/io/buffer.hh
@@ -1,3 +1,12 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: buffer.hh
+// Description: QDataStream-esque buffer
+
+#ifndef CORE_IO_BUFFER_HH
+#define CORE_IO_BUFFER_HH
+#pragma once
+
 class ReadBuffer final {
 public:
     ReadBuffer(void) = default;
@@ -80,3 +89,5 @@ WriteBuffer& WriteBuffer::operator<<(const T value)
     write<T>(value);
     return *this;
 }
+
+#endif
diff --git a/src/core/io/cmdline.cc b/src/core/io/cmdline.cc
index d206cb8..0d1206a 100644
--- a/src/core/io/cmdline.cc
+++ b/src/core/io/cmdline.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: cmdline.cc
+// Description: Command-line arguments parser
+
 #include "core/pch.hh"
 
 #include "core/io/cmdline.hh"
diff --git a/src/core/io/cmdline.hh b/src/core/io/cmdline.hh
index c0d6db2..452072f 100644
--- a/src/core/io/cmdline.hh
+++ b/src/core/io/cmdline.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: cmdline.hh
+// Description: Command-line arguments parser
+
+#ifndef CORE_IO_CMDLINE_HH
+#define CORE_IO_CMDLINE_HH
 #pragma once
 
 namespace cmdline
@@ -9,3 +16,5 @@ std::string_view get(std::string_view option, std::string_view fallback = "");
 const char* get_cstr(std::string_view option, const char* fallback = nullptr);
 bool contains(std::string_view option);
 } // namespace cmdline
+
+#endif
diff --git a/src/core/io/config_map.cc b/src/core/io/config_map.cc
index 8634fd6..93fab2b 100644
--- a/src/core/io/config_map.cc
+++ b/src/core/io/config_map.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: config_map.cc
+// Description: Config parser
+
 #include "core/pch.hh"
 
 #include "core/io/config_map.hh"
diff --git a/src/core/io/config_map.hh b/src/core/io/config_map.hh
index 898103b..2e3f18f 100644
--- a/src/core/io/config_map.hh
+++ b/src/core/io/config_map.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: config_map.hh
+// Description: Config parser
+
+#ifndef CORE_IO_CONFIG_MAP_HH
+#define CORE_IO_CONFIG_MAP_HH
 #pragma once
 
 namespace config
@@ -24,3 +31,5 @@ public:
 private:
     std::unordered_map<std::string, config::IValue*> m_values;
 };
+
+#endif
diff --git a/src/core/io/physfs.cc b/src/core/io/physfs.cc
index b9fe91e..04aaf64 100644
--- a/src/core/io/physfs.cc
+++ b/src/core/io/physfs.cc
@@ -1,13 +1,18 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: physfs.cc
+// Description: PhysFS utilities
+
 #include "core/pch.hh"
 
 #include "core/io/physfs.hh"
 
-bool read_file(std::string_view path, std::vector<std::byte>& buffer)
+bool physfs::read_file(std::string_view path, std::vector<std::byte>& buffer)
 {
     auto file = PHYSFS_openRead(std::string(path).c_str());
 
     if(file == nullptr) {
-        spdlog::error("physfs: {}: {}", path, physfs_error());
+        spdlog::error("physfs: {}: {}", path, physfs::last_error());
         return false;
     }
 
@@ -20,12 +25,12 @@ bool read_file(std::string_view path, std::vector<std::byte>& buffer)
     return true;
 }
 
-bool read_file(std::string_view path, std::string& buffer)
+bool physfs::read_file(std::string_view path, std::string& buffer)
 {
     auto file = PHYSFS_openRead(std::string(path).c_str());
 
     if(file == nullptr) {
-        spdlog::error("physfs: {}: {}", path, physfs_error());
+        spdlog::error("physfs: {}: {}", path, physfs::last_error());
         return false;
     }
 
@@ -38,12 +43,12 @@ bool read_file(std::string_view path, std::string& buffer)
     return true;
 }
 
-bool write_file(std::string_view path, const std::vector<std::byte>& buffer)
+bool physfs::write_file(std::string_view path, const std::vector<std::byte>& buffer)
 {
     auto file = PHYSFS_openWrite(std::string(path).c_str());
 
     if(file == nullptr) {
-        spdlog::error("physfs: {}: {}", path, physfs_error());
+        spdlog::error("physfs: {}: {}", path, physfs::last_error());
         return false;
     }
 
@@ -53,12 +58,12 @@ bool write_file(std::string_view path, const std::vector<std::byte>& buffer)
     return true;
 }
 
-bool write_file(std::string_view path, const std::string& buffer)
+bool physfs::write_file(std::string_view path, const std::string& buffer)
 {
     auto file = PHYSFS_openWrite(std::string(path).c_str());
 
     if(file == nullptr) {
-        spdlog::error("physfs: {}: {}", path, physfs_error());
+        spdlog::error("physfs: {}: {}", path, physfs::last_error());
         return false;
     }
 
@@ -68,7 +73,7 @@ bool write_file(std::string_view path, const std::string& buffer)
     return true;
 }
 
-std::string_view physfs_error(void)
+std::string_view physfs::last_error(void)
 {
     auto error_code = PHYSFS_getLastErrorCode();
     auto error_string = PHYSFS_getErrorByCode(error_code);
diff --git a/src/core/io/physfs.hh b/src/core/io/physfs.hh
index 88f97de..8cf84be 100644
--- a/src/core/io/physfs.hh
+++ b/src/core/io/physfs.hh
@@ -1,8 +1,23 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: physfs.hh
+// Description: PhysFS utilities
+
+#ifndef CORE_IO_PHYSFS_HH
+#define CORE_IO_PHYSFS_HH
 #pragma once
 
+namespace physfs
+{
 bool read_file(std::string_view path, std::vector<std::byte>& buffer);
 bool read_file(std::string_view path, std::string& buffer);
 bool write_file(std::string_view path, const std::vector<std::byte>& buffer);
 bool write_file(std::string_view path, const std::string& buffer);
+} // namespace physfs
+
+namespace physfs
+{
+std::string_view last_error(void);
+} // namespace physfs
 
-std::string_view physfs_error(void);
+#endif
diff --git a/src/core/math/aabb.hh b/src/core/math/aabb.hh
index f3eb7bd..79f814a 100644
--- a/src/core/math/aabb.hh
+++ b/src/core/math/aabb.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: aabb.hh
+// Description: Axis-aligned bounding box
+
+#ifndef CORE_MATH_AABB_HH
+#define CORE_MATH_AABB_HH
 #pragma once
 
 #include "core/math/concepts.hh"
@@ -109,3 +116,5 @@ constexpr math::AABB<T> math::AABB<T>::push(const vector_type& vector) const
     result.max = max + vector;
     return result;
 }
+
+#endif
diff --git a/src/core/math/angles.hh b/src/core/math/angles.hh
index 174f320..b339323 100644
--- a/src/core/math/angles.hh
+++ b/src/core/math/angles.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: angles.hh
+// Description: Angle utilities
+
+#ifndef CORE_MATH_ANGLES_HH
+#define CORE_MATH_ANGLES_HH
 #pragma once
 
 #include "core/math/constexpr.hh"
@@ -101,3 +108,5 @@ inline void math::vectors(const glm::fvec3& angles, glm::fvec3* forward, glm::fv
         up->z = nsv.x * ncv.y * pcv.z + psv.y * psv.z;
     }
 }
+
+#endif
diff --git a/src/core/math/concepts.hh b/src/core/math/concepts.hh
index 6ad5cb7..5d1ef7d 100644
--- a/src/core/math/concepts.hh
+++ b/src/core/math/concepts.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: concepts.hh
+// Description: C++20 concepts that should be in standard library but are not
+
+#ifndef CORE_MATH_CONCEPTS_HH
+#define CORE_MATH_CONCEPTS_HH
 #pragma once
 
 namespace math
@@ -9,3 +16,5 @@ concept signed_arithmetic = std::is_arithmetic_v<type> && std::is_signed_v<type>
 template<typename type>
 concept unsigned_arithmetic = std::is_arithmetic_v<type> && std::is_unsigned_v<type>;
 } // namespace math
+
+#endif
diff --git a/src/core/math/constexpr.hh b/src/core/math/constexpr.hh
index 4158803..7aba4d2 100644
--- a/src/core/math/constexpr.hh
+++ b/src/core/math/constexpr.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: constexpr.hh
+// Description: Compile-time expressions
+
+#ifndef CORE_MATH_CONSTEXPR_HH
+#define CORE_MATH_CONSTEXPR_HH
 #pragma once
 
 #include "core/math/concepts.hh"
@@ -70,3 +77,5 @@ constexpr scalar math::radians(const scalar x)
 {
     return static_cast<scalar>(static_cast<double>(x) * M_PI / 180.0);
 }
+
+#endif
diff --git a/src/core/math/crc64.cc b/src/core/math/crc64.cc
index 99a4b20..ce1e1db 100644
--- a/src/core/math/crc64.cc
+++ b/src/core/math/crc64.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: crc64.cc
+// Description: Client-server synchronized CRC64
+
 #include "core/pch.hh"
 
 #include "core/math/crc64.hh"
diff --git a/src/core/math/crc64.hh b/src/core/math/crc64.hh
index 3ece0df..f593dc9 100644
--- a/src/core/math/crc64.hh
+++ b/src/core/math/crc64.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: crc64.hh
+// Description: Client-server synchronized CRC64
+
+#ifndef CORE_MATH_CRC64_HH
+#define CORE_MATH_CRC64_HH
 #pragma once
 
 namespace math
@@ -7,3 +14,5 @@ std::uint64_t crc64(const std::vector<std::byte>& buffer, std::uint64_t combine
 std::uint64_t crc64(const std::string& buffer, std::uint64_t combine = UINT64_C(0));
 std::uint64_t crc64(std::string_view buffer, std::uint64_t combine = UINT64_C(0));
 } // namespace math
+
+#endif
diff --git a/src/core/math/vectors.hh b/src/core/math/vectors.hh
index bc11dd0..2934bb6 100644
--- a/src/core/math/vectors.hh
+++ b/src/core/math/vectors.hh
@@ -1,11 +1,14 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: vectors.hh
+// Description: because NO ONE would POSSIBLY need integer-based distance calculations in a VOXEL game
+
+#ifndef CORE_MATH_VECTORS_HH
+#define CORE_MATH_VECTORS_HH
 #pragma once
 
 #include "core/math/concepts.hh"
 
-// core/vectors.hh - because NO ONE would POSSIBLY
-// need integer-based distance calculations in a
-// game about voxels. That would be INSANE! :D
-
 namespace math
 {
 template<math::arithmetic T>
@@ -41,3 +44,5 @@ constexpr static inline const T math::distance2(const glm::vec<3, T>& vector_a,
 {
     return math::length2(vector_a - vector_b);
 }
+
+#endif
diff --git a/src/core/pch.hh b/src/core/pch.hh
index 17417a5..9a99be7 100644
--- a/src/core/pch.hh
+++ b/src/core/pch.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: pch.hh
+// Description: Precompiled header
+
+#ifndef CORE_PCH_HH
+#define CORE_PCH_HH
 #pragma once
 
 #include <cinttypes>
@@ -47,3 +54,5 @@
 
 #include <stb_image.h>
 #include <stb_image_write.h>
+
+#endif
diff --git a/src/core/resource/image.cc b/src/core/resource/image.cc
index 6a2109e..aded098 100644
--- a/src/core/resource/image.cc
+++ b/src/core/resource/image.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: image.cc
+// Description: Image resource
+
 #include "core/pch.hh"
 
 #include "core/resource/image.hh"
@@ -31,18 +36,18 @@ static const void* image_load_func(const char* name, std::uint32_t flags)
     callbacks.skip = &stbi_physfs_skip;
     callbacks.eof = &stbi_physfs_eof;
 
-    stbi_set_flip_vertically_on_load(bool(flags & IMAGE_LOAD_FLIP));
+    stbi_set_flip_vertically_on_load(bool(flags & IMGFLAG_FLIP));
 
     auto file = PHYSFS_openRead(name);
 
     if(file == nullptr) {
-        spdlog::error("image: {}: {}", name, physfs_error());
+        spdlog::error("image: {}: {}", name, physfs::last_error());
         return nullptr;
     }
 
     int desired_channels;
 
-    if(flags & IMAGE_LOAD_GRAY) {
+    if(flags & IMGFLAG_GRAY) {
         desired_channels = STBI_grey;
     }
     else {
diff --git a/src/core/resource/image.hh b/src/core/resource/image.hh
index 575591f..4f93da6 100644
--- a/src/core/resource/image.hh
+++ b/src/core/resource/image.hh
@@ -1,7 +1,14 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: image.hh
+// Description: Image resource
+
+#ifndef CORE_RESOURCE_IMAGE_HH
+#define CORE_RESOURCE_IMAGE_HH
 #pragma once
 
-constexpr static unsigned int IMAGE_LOAD_GRAY = 0x0001U;
-constexpr static unsigned int IMAGE_LOAD_FLIP = 0x0002U;
+constexpr static unsigned int IMGFLAG_GRAY = 0x0001U;
+constexpr static unsigned int IMGFLAG_FLIP = 0x0002U;
 
 struct Image final {
     static void register_resource(void);
@@ -9,3 +16,5 @@ struct Image final {
     stbi_uc* pixels;
     glm::ivec2 size;
 };
+
+#endif
diff --git a/src/core/resource/resource.cc b/src/core/resource/resource.cc
index 926dfc5..6a9539f 100644
--- a/src/core/resource/resource.cc
+++ b/src/core/resource/resource.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: resource.cc
+// Description: Resource management
+
 #include "core/pch.hh"
 
 #include "core/resource/resource.hh"
diff --git a/src/core/resource/resource.hh b/src/core/resource/resource.hh
index 105c7ff..e2a5659 100644
--- a/src/core/resource/resource.hh
+++ b/src/core/resource/resource.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: resource.hh
+// Description: Resource management
+
+#ifndef CORE_RESOURCE_RESOURCE_HH
+#define CORE_RESOURCE_RESOURCE_HH
 #pragma once
 
 template<typename T>
@@ -51,3 +58,5 @@ resource_ptr<T> resource::find(std::string_view name)
     auto result = resource::detail::find_resource(typeid(T), name);
     return std::reinterpret_pointer_cast<const T>(result);
 }
+
+#endif
diff --git a/src/core/threading.cc b/src/core/threading.cc
index a1ae305..1e469ad 100644
--- a/src/core/threading.cc
+++ b/src/core/threading.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: threading.cc
+// Description: Thread pool wrapper
+
 #include "core/pch.hh"
 
 #include "core/threading.hh"
diff --git a/src/core/threading.hh b/src/core/threading.hh
index 14f17f8..ea4e11b 100644
--- a/src/core/threading.hh
+++ b/src/core/threading.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: threading.hh
+// Description: Thread pool wrapper
+
+#ifndef CORE_THREADING_HH
+#define CORE_THREADING_HH
 #pragma once
 
 enum class task_status : unsigned int {
@@ -44,3 +51,5 @@ inline void threading::submit(AT&&... args)
 {
     threading::detail::submit_new(new T(args...));
 }
+
+#endif
diff --git a/src/core/utils/epoch.cc b/src/core/utils/epoch.cc
index 36bdb79..9d66399 100644
--- a/src/core/utils/epoch.cc
+++ b/src/core/utils/epoch.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: epoch.cc
+// Description: UNIX time utilities
+
 #include "core/pch.hh"
 
 #include "core/utils/epoch.hh"
diff --git a/src/core/utils/epoch.hh b/src/core/utils/epoch.hh
index 4bf5460..5210e22 100644
--- a/src/core/utils/epoch.hh
+++ b/src/core/utils/epoch.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: epoch.hh
+// Description: UNIX time utilities
+
+#ifndef CORE_UTILS_EPOCH_HH
+#define CORE_UTILS_EPOCH_HH
 #pragma once
 
 namespace utils
@@ -13,3 +20,5 @@ std::int64_t signed_unix_seconds(void);
 std::int64_t signed_unix_milliseconds(void);
 std::int64_t signed_unix_microseconds(void);
 } // namespace utils
+
+#endif
diff --git a/src/core/utils/string.cc b/src/core/utils/string.cc
index dd3d567..154b04b 100644
--- a/src/core/utils/string.cc
+++ b/src/core/utils/string.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: string.cc
+// Description: String utilities
+
 #include "core/pch.hh"
 
 #include "core/utils/string.hh"
diff --git a/src/core/utils/string.hh b/src/core/utils/string.hh
index 827c3ca..36c83ce 100644
--- a/src/core/utils/string.hh
+++ b/src/core/utils/string.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: string.hh
+// Description: String utilities
+
+#ifndef CORE_UTILS_STRING_HH
+#define CORE_UTILS_STRING_HH
 #pragma once
 
 namespace utils
@@ -15,3 +22,5 @@ namespace utils
 {
 std::string trim_whitespace(const std::string& string);
 } // namespace utils
+
+#endif
diff --git a/src/core/version.cc.in b/src/core/version.cc.in
index 5424a73..d791149 100644
--- a/src/core/version.cc.in
+++ b/src/core/version.cc.in
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: version.cc.in
+// Description: Version template
+
 #include "core/pch.hh"
 
 #include "core/version.hh"
diff --git a/src/core/version.hh b/src/core/version.hh
index c033a3e..d040fa5 100644
--- a/src/core/version.hh
+++ b/src/core/version.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: version.hh
+// Description: Version information
+
+#ifndef CORE_VERSION_HH
+#define CORE_VERSION_HH
 #pragma once
 
 namespace version
@@ -18,3 +25,5 @@ namespace version
 {
 extern const std::string_view full;
 } // namespace version
+
+#endif
diff --git a/src/game/client/config/gamepad_axis.cc b/src/game/client/config/gamepad_axis.cc
index 4eb36a9..db66fc0 100644
--- a/src/game/client/config/gamepad_axis.cc
+++ b/src/game/client/config/gamepad_axis.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: gamepad_axis.cc
+// Description: Gamepad axis config value
+
 #include "client/pch.hh"
 
 #include "client/config/gamepad_axis.hh"
diff --git a/src/game/client/config/gamepad_axis.hh b/src/game/client/config/gamepad_axis.hh
index 9392a35..1ca7706 100644
--- a/src/game/client/config/gamepad_axis.hh
+++ b/src/game/client/config/gamepad_axis.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: gamepad_axis.hh
+// Description: Gamepad axis config value
+
+#ifndef CLIENT_CONFIG_GAMEPAD_AXIS_HH
+#define CLIENT_CONFIG_GAMEPAD_AXIS_HH
 #pragma once
 
 #include "core/config/ivalue.hh"
@@ -36,3 +43,5 @@ private:
     std::string_view m_name;
 };
 } // namespace config
+
+#endif
diff --git a/src/game/client/config/gamepad_button.cc b/src/game/client/config/gamepad_button.cc
index d3f8a25..dce0fc2 100644
--- a/src/game/client/config/gamepad_button.cc
+++ b/src/game/client/config/gamepad_button.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: gamepad_button.cc
+// Description: Gamepad button config value
+
 #include "client/pch.hh"
 
 #include "client/config/gamepad_button.hh"
diff --git a/src/game/client/config/gamepad_button.hh b/src/game/client/config/gamepad_button.hh
index 584c353..43a1f4b 100644
--- a/src/game/client/config/gamepad_button.hh
+++ b/src/game/client/config/gamepad_button.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: gamepad_button.hh
+// Description: Gamepad button config value
+
+#ifndef CLIENT_CONFIG_GAMEPAD_BUTTON_HH
+#define CLIENT_CONFIG_GAMEPAD_BUTTON_HH
 #pragma once
 
 #include "core/config/ivalue.hh"
@@ -26,3 +33,5 @@ private:
     std::string_view m_name;
 };
 } // namespace config
+
+#endif
diff --git a/src/game/client/config/keybind.cc b/src/game/client/config/keybind.cc
index e254f7b..194bb87 100644
--- a/src/game/client/config/keybind.cc
+++ b/src/game/client/config/keybind.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: keybind.cc
+// Description: Key binding config value
+
 #include "client/pch.hh"
 
 #include "client/config/keybind.hh"
diff --git a/src/game/client/config/keybind.hh b/src/game/client/config/keybind.hh
index dff6c18..af69865 100644
--- a/src/game/client/config/keybind.hh
+++ b/src/game/client/config/keybind.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: keybind.hh
+// Description: Key binding config value
+
+#ifndef CLIENT_CONFIG_KEYBIND_HH
+#define CLIENT_CONFIG_KEYBIND_HH
 #pragma once
 
 #include "core/config/ivalue.hh"
@@ -23,3 +30,5 @@ private:
     int m_glfw_keycode;
 };
 } // namespace config
+
+#endif
diff --git a/src/game/client/const.hh b/src/game/client/const.hh
index 709c0a1..c6b1538 100644
--- a/src/game/client/const.hh
+++ b/src/game/client/const.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: const.hh
+// Description: Constants
+
+#ifndef CLIENT_CONST_HH
+#define CLIENT_CONST_HH
 #pragma once
 
 #include "shared/const.hh"
@@ -21,3 +28,5 @@ static_assert(DEFAULT_HEIGHT >= MIN_HEIGHT);
 
 constexpr static float MIN_PITCH = 0.0625f;
 constexpr static float MAX_PITCH = 10.0f;
+
+#endif
diff --git a/src/game/client/entity/camera.cc b/src/game/client/entity/camera.cc
index 27603cf..8cd08fd 100644
--- a/src/game/client/entity/camera.cc
+++ b/src/game/client/entity/camera.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: camera.cc
+// Description: Client view matrix calculations
+
 #include "client/pch.hh"
 
 #include "client/entity/camera.hh"
diff --git a/src/game/client/entity/camera.hh b/src/game/client/entity/camera.hh
index 526bc91..133fedc 100644
--- a/src/game/client/entity/camera.hh
+++ b/src/game/client/entity/camera.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: camera.hh
+// Description: Client view matrix calculations
+
+#ifndef CLIENT_ENTITY_CAMERA_HH
+#define CLIENT_ENTITY_CAMERA_HH
 #pragma once
 
 #include "shared/types.hh"
@@ -29,3 +36,5 @@ namespace camera
 void init(void);
 void update(void);
 } // namespace camera
+
+#endif
diff --git a/src/game/client/entity/factory.cc b/src/game/client/entity/factory.cc
index 94a9698..019d855 100644
--- a/src/game/client/entity/factory.cc
+++ b/src/game/client/entity/factory.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: factory.cc
+// Description: Boilerplate entity creation
+
 #include "client/pch.hh"
 
 #include "client/entity/factory.hh"
diff --git a/src/game/client/entity/factory.hh b/src/game/client/entity/factory.hh
index 776a0b8..20714ff 100644
--- a/src/game/client/entity/factory.hh
+++ b/src/game/client/entity/factory.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: factory.hh
+// Description: Boilerplate entity creation
+
+#ifndef CLIENT_ENTITY_FACTORY_HH
+#define CLIENT_ENTITY_FACTORY_HH
 #pragma once
 
 class Dimension;
@@ -6,3 +13,5 @@ namespace client
 {
 void create_player(Dimension* dimension, entt::entity entity);
 } // namespace client
+
+#endif
diff --git a/src/game/client/entity/interpolation.cc b/src/game/client/entity/interpolation.cc
index 86af971..b1318c9 100644
--- a/src/game/client/entity/interpolation.cc
+++ b/src/game/client/entity/interpolation.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: interpolation.cc
+// Description: Interpolate components between server frames
+
 #include "client/pch.hh"
 
 #include "client/entity/interpolation.hh"
diff --git a/src/game/client/entity/interpolation.hh b/src/game/client/entity/interpolation.hh
index 8fb0db1..cc18b23 100644
--- a/src/game/client/entity/interpolation.hh
+++ b/src/game/client/entity/interpolation.hh
@@ -1,6 +1,15 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: interpolation.hh
+// Description: Interpolate components between server frames
+
+#ifndef CLIENT_ENTITY_INTERPOLATION_HH
+#define CLIENT_ENTITY_INTERPOLATION_HH
 #pragma once
 
 namespace interpolation
 {
 void update(void);
 } // namespace interpolation
+
+#endif
diff --git a/src/game/client/entity/listener.cc b/src/game/client/entity/listener.cc
index af574ae..e411f72 100644
--- a/src/game/client/entity/listener.cc
+++ b/src/game/client/entity/listener.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: listener.cc
+// Description: OpenAL listener
+
 #include "client/pch.hh"
 
 #include "client/entity/listener.hh"
diff --git a/src/game/client/entity/listener.hh b/src/game/client/entity/listener.hh
index 07d750f..d4391e2 100644
--- a/src/game/client/entity/listener.hh
+++ b/src/game/client/entity/listener.hh
@@ -1,6 +1,15 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: listener.hh
+// Description: OpenAL listener
+
+#ifndef CLIENT_ENTITY_LISTENER_HH
+#define CLIENT_ENTITY_LISTENER_HH
 #pragma once
 
 namespace listener
 {
 void update(void);
 } // namespace listener
+
+#endif
diff --git a/src/game/client/entity/player_look.cc b/src/game/client/entity/player_look.cc
index ad0f40e..c3b7dbd 100644
--- a/src/game/client/entity/player_look.cc
+++ b/src/game/client/entity/player_look.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: player_look.cc
+// Description: Client camera rotations
+
 #include "client/pch.hh"
 
 #include "client/entity/player_look.hh"
diff --git a/src/game/client/entity/player_look.hh b/src/game/client/entity/player_look.hh
index 9d0f1dd..1bb0190 100644
--- a/src/game/client/entity/player_look.hh
+++ b/src/game/client/entity/player_look.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: player_look.hh
+// Description: Client camera rotations
+
+#ifndef CLIENT_ENTITY_PLAYER_LOOK_HH
+#define CLIENT_ENTITY_PLAYER_LOOK_HH
 #pragma once
 
 namespace player_look
@@ -5,3 +12,5 @@ namespace player_look
 void init(void);
 void update_late(void);
 } // namespace player_look
+
+#endif
diff --git a/src/game/client/entity/player_move.cc b/src/game/client/entity/player_move.cc
index fe4e757..663258f 100644
--- a/src/game/client/entity/player_move.cc
+++ b/src/game/client/entity/player_move.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: player_move.cc
+// Description: Player movement
+
 #include "client/pch.hh"
 
 #include "client/entity/player_move.hh"
diff --git a/src/game/client/entity/player_move.hh b/src/game/client/entity/player_move.hh
index 8516308..6e9fa44 100644
--- a/src/game/client/entity/player_move.hh
+++ b/src/game/client/entity/player_move.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: player_move.hh
+// Description: Player movement
+
+#ifndef CLIENT_ENTITY_PLAYER_MOVE_HH
+#define CLIENT_ENTITY_PLAYER_MOVE_HH
 #pragma once
 
 constexpr static float PMOVE_MAX_SPEED_AIR = 16.0f;
@@ -13,3 +20,5 @@ void init(void);
 void fixed_update(void);
 void update_late(void);
 } // namespace player_move
+
+#endif
diff --git a/src/game/client/entity/sound_emitter.cc b/src/game/client/entity/sound_emitter.cc
index b0dbc6d..313da0b 100644
--- a/src/game/client/entity/sound_emitter.cc
+++ b/src/game/client/entity/sound_emitter.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: sound_emitter.cc
+// Description: Component for entities that make sounds
+
 #include "client/pch.hh"
 
 #include "client/entity/sound_emitter.hh"
diff --git a/src/game/client/entity/sound_emitter.hh b/src/game/client/entity/sound_emitter.hh
index 6bc0846..b89c651 100644
--- a/src/game/client/entity/sound_emitter.hh
+++ b/src/game/client/entity/sound_emitter.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: sound_emitter.hh
+// Description: Component for entities that make sounds
+
+#ifndef CLIENT_ENTITY_SOUND_EMITTER_HH
+#define CLIENT_ENTITY_SOUND_EMITTER_HH
 #pragma once
 
 #include "core/resource/resource.hh"
@@ -15,3 +22,5 @@ public:
 public:
     static void update(void);
 };
+
+#endif
diff --git a/src/game/client/experiments.cc b/src/game/client/experiments.cc
index 4df6f1e..dcd3c7d 100644
--- a/src/game/client/experiments.cc
+++ b/src/game/client/experiments.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: experiments.cc
+// Description: Experimental things that are still haven't got their dedicated game system
+
 #include "client/pch.hh"
 
 #include "client/experiments.hh"
diff --git a/src/game/client/experiments.hh b/src/game/client/experiments.hh
index ff2cbad..c3415ba 100644
--- a/src/game/client/experiments.hh
+++ b/src/game/client/experiments.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: experiments.hh
+// Description: Experimental things that are still haven't got their dedicated game system
+
+#ifndef CLIENT_EXPERIMENTS_HH
+#define CLIENT_EXPERIMENTS_HH
 #pragma once
 
 namespace experiments
@@ -14,3 +21,5 @@ namespace experiments
 void attack(void);
 void interact(void);
 } // namespace experiments
+
+#endif
diff --git a/src/game/client/game.cc b/src/game/client/game.cc
index 6219ff9..09445c4 100644
--- a/src/game/client/game.cc
+++ b/src/game/client/game.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: game.cc
+// Description: Main game logic
+
 #include "client/pch.hh"
 
 #include "client/game.hh"
@@ -104,8 +109,8 @@ static ImFont* load_font(std::string_view path, float size, ImFontConfig& font_c
 {
     std::vector<std::byte> font;
 
-    if(!read_file(path, font)) {
-        spdlog::error("{}: utils::read_file failed", path);
+    if(!physfs::read_file(path, font)) {
+        spdlog::error("{}: utils::physfs::read_file failed", path);
         std::terminate();
     }
 
diff --git a/src/game/client/game.hh b/src/game/client/game.hh
index 395acc9..7ed663b 100644
--- a/src/game/client/game.hh
+++ b/src/game/client/game.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: game.hh
+// Description: Main game logic
+
+#ifndef CLIENT_GAME_HH
+#define CLIENT_GAME_HH
 #pragma once
 
 namespace config
@@ -33,3 +40,5 @@ void update_late(void);
 void render(void);
 void layout(void);
 } // namespace client_game
+
+#endif
diff --git a/src/game/client/globals.cc b/src/game/client/globals.cc
index 85e5cd6..4e16107 100644
--- a/src/game/client/globals.cc
+++ b/src/game/client/globals.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: globals.cc
+// Description: Global variables
+
 #include "client/pch.hh"
 
 #include "client/globals.hh"
diff --git a/src/game/client/globals.hh b/src/game/client/globals.hh
index a6c2de6..a471097 100644
--- a/src/game/client/globals.hh
+++ b/src/game/client/globals.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: globals.hh
+// Description: Global variables
+
+#ifndef CLIENT_GLOBALS_HH
+#define CLIENT_GLOBALS_HH
 #pragma once
 
 #include "shared/globals.hh"
@@ -63,3 +70,5 @@ extern unsigned int gui_screen;
 extern ALCdevice* sound_dev;
 extern ALCcontext* sound_ctx;
 } // namespace globals
+
+#endif
diff --git a/src/game/client/gui/background.cc b/src/game/client/gui/background.cc
index 81fb764..e0e0684 100644
--- a/src/game/client/gui/background.cc
+++ b/src/game/client/gui/background.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: background.cc
+// Description: Background texture rendering when you're not in-game
+
 #include "client/pch.hh"
 
 #include "client/gui/background.hh"
diff --git a/src/game/client/gui/background.hh b/src/game/client/gui/background.hh
index 51497d1..1f7fef9 100644
--- a/src/game/client/gui/background.hh
+++ b/src/game/client/gui/background.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: background.hh
+// Description: Background texture rendering when you're not in-game
+
+#ifndef CLIENT_GUI_BACKGROUND_HH
+#define CLIENT_GUI_BACKGROUND_HH
 #pragma once
 
 namespace background
@@ -6,3 +13,5 @@ void init(void);
 void shutdown(void);
 void layout(void);
 } // namespace background
+
+#endif
diff --git a/src/game/client/gui/bother.cc b/src/game/client/gui/bother.cc
index 7309bbc..2308b4a 100644
--- a/src/game/client/gui/bother.cc
+++ b/src/game/client/gui/bother.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: bother.cc
+// Description: Bother servers with a status request
+
 #include "client/pch.hh"
 
 #include "client/gui/bother.hh"
diff --git a/src/game/client/gui/bother.hh b/src/game/client/gui/bother.hh
index ed4f84f..d702bde 100644
--- a/src/game/client/gui/bother.hh
+++ b/src/game/client/gui/bother.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: bother.hh
+// Description: Bother servers with a status request
+
+#ifndef CLIENT_GUI_BOTHER_HH
+#define CLIENT_GUI_BOTHER_HH
 #pragma once
 
 struct BotherResponseEvent final {
@@ -19,3 +26,5 @@ void update_late(void);
 void ping(unsigned int identity, std::string_view host, std::uint16_t port);
 void cancel(unsigned int identity);
 } // namespace bother
+
+#endif
diff --git a/src/game/client/gui/chat.cc b/src/game/client/gui/chat.cc
index f962e5d..9613aa5 100644
--- a/src/game/client/gui/chat.cc
+++ b/src/game/client/gui/chat.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chat.cc
+// Description: Client chat handling
+
 #include "client/pch.hh"
 
 #include "client/gui/chat.hh"
diff --git a/src/game/client/gui/chat.hh b/src/game/client/gui/chat.hh
index 91c3740..afe1965 100644
--- a/src/game/client/gui/chat.hh
+++ b/src/game/client/gui/chat.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chat.hh
+// Description: Client chat handling
+
+#ifndef CLIENT_GUI_CHAT_HH
+#define CLIENT_GUI_CHAT_HH
 #pragma once
 
 namespace client_chat
@@ -15,3 +22,5 @@ void clear(void);
 void refresh_timings(void);
 void print(const std::string& string);
 } // namespace client_chat
+
+#endif
diff --git a/src/game/client/gui/crosshair.cc b/src/game/client/gui/crosshair.cc
index 088796d..29314b9 100644
--- a/src/game/client/gui/crosshair.cc
+++ b/src/game/client/gui/crosshair.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: crosshair.cc
+// Description: Crosshair rendering
+
 #include "client/pch.hh"
 
 #include "client/gui/crosshair.hh"
diff --git a/src/game/client/gui/crosshair.hh b/src/game/client/gui/crosshair.hh
index 6789e1e..0775bb2 100644
--- a/src/game/client/gui/crosshair.hh
+++ b/src/game/client/gui/crosshair.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: crosshair.hh
+// Description: Crosshair rendering
+
+#ifndef CLIENT_GUI_CROSSHAIR_HH
+#define CLIENT_GUI_CROSSHAIR_HH
 #pragma once
 
 namespace crosshair
@@ -6,3 +13,5 @@ void init(void);
 void shutdown(void);
 void layout(void);
 } // namespace crosshair
+
+#endif
diff --git a/src/game/client/gui/direct_connection.cc b/src/game/client/gui/direct_connection.cc
index d7cea64..2b75a44 100644
--- a/src/game/client/gui/direct_connection.cc
+++ b/src/game/client/gui/direct_connection.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: direct_connection.cc
+// Description: Direct connection screen
+
 #include "client/pch.hh"
 
 #include "client/gui/direct_connection.hh"
diff --git a/src/game/client/gui/direct_connection.hh b/src/game/client/gui/direct_connection.hh
index 0a09a3f..609e326 100644
--- a/src/game/client/gui/direct_connection.hh
+++ b/src/game/client/gui/direct_connection.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: direct_connection.hh
+// Description: Direct connection screen
+
+#ifndef CLIENT_GUI_DIRECT_CONNECTION_HH
+#define CLIENT_GUI_DIRECT_CONNECTION_HH
 #pragma once
 
 namespace direct_connection
@@ -5,3 +12,5 @@ namespace direct_connection
 void init(void);
 void layout(void);
 } // namespace direct_connection
+
+#endif
diff --git a/src/game/client/gui/gui_screen.hh b/src/game/client/gui/gui_screen.hh
index 2eae310..7a1da10 100644
--- a/src/game/client/gui/gui_screen.hh
+++ b/src/game/client/gui/gui_screen.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: gui_screen.hh
+// Description: GUI screen constants
+
+#ifndef CLIENT_GUI_GUI_SCREEN_HH
+#define CLIENT_GUI_GUI_SCREEN_HH
 #pragma once
 
 constexpr static unsigned int GUI_SCREEN_NONE = 0x0000U;
@@ -8,3 +15,5 @@ constexpr static unsigned int GUI_PROGRESS_BAR = 0x0004U;
 constexpr static unsigned int GUI_MESSAGE_BOX = 0x0005U;
 constexpr static unsigned int GUI_CHAT = 0x0006U;
 constexpr static unsigned int GUI_DIRECT_CONNECTION = 0x0007U;
+
+#endif
diff --git a/src/game/client/gui/hotbar.cc b/src/game/client/gui/hotbar.cc
index b38c368..edcf8a9 100644
--- a/src/game/client/gui/hotbar.cc
+++ b/src/game/client/gui/hotbar.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: hotbar.cc
+// Description: Hotbar rendering
+
 #include "client/pch.hh"
 
 #include "client/gui/hotbar.hh"
diff --git a/src/game/client/gui/hotbar.hh b/src/game/client/gui/hotbar.hh
index bba5e63..54e53d5 100644
--- a/src/game/client/gui/hotbar.hh
+++ b/src/game/client/gui/hotbar.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: hotbar.hh
+// Description: Hotbar rendering
+
+#ifndef CLIENT_GUI_HOTBAR_HH
+#define CLIENT_GUI_HOTBAR_HH
 #pragma once
 
 // TODO: design an inventory system and an item
@@ -25,3 +32,5 @@ namespace hotbar
 void next_slot(void);
 void prev_slot(void);
 } // namespace hotbar
+
+#endif
diff --git a/src/game/client/gui/imutils_button.cc b/src/game/client/gui/imutils_button.cc
index 2017e33..05da90e 100644
--- a/src/game/client/gui/imutils_button.cc
+++ b/src/game/client/gui/imutils_button.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: imutils_button.cc
+// Description: Extended button layout
+
 #include "client/pch.hh"
 
 #include "client/gui/imutils_button.hh"
diff --git a/src/game/client/gui/imutils_button.hh b/src/game/client/gui/imutils_button.hh
index 0c80694..602b723 100644
--- a/src/game/client/gui/imutils_button.hh
+++ b/src/game/client/gui/imutils_button.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: imutils_button.hh
+// Description: Extended button layout
+
+#ifndef CLIENT_GUI_IMUTILS_BUTTON_HH
+#define CLIENT_GUI_IMUTILS_BUTTON_HH
 #pragma once
 
 namespace imutils
@@ -12,3 +19,5 @@ bool selectable_button(const char* label, const ImVec2& size, bool value);
 bool toggle_button(const char* label, const ImVec2& size, bool& value);
 bool toggle_button(const char* label, bool& value);
 } // namespace imutils
+
+#endif
diff --git a/src/game/client/gui/imutils_popup.cc b/src/game/client/gui/imutils_popup.cc
index f97facb..ba997d5 100644
--- a/src/game/client/gui/imutils_popup.cc
+++ b/src/game/client/gui/imutils_popup.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: imutils_popup.cc
+// Description: Popup utilities
+
 #include "client/pch.hh"
 
 #include "client/gui/imutils_popup.hh"
diff --git a/src/game/client/gui/imutils_popup.hh b/src/game/client/gui/imutils_popup.hh
index 1678f87..159503b 100644
--- a/src/game/client/gui/imutils_popup.hh
+++ b/src/game/client/gui/imutils_popup.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: imutils_popup.hh
+// Description: Popup utilities
+
+#ifndef CLIENT_GUI_IMUTILS_POPUP_HH
+#define CLIENT_GUI_IMUTILS_POPUP_HH
 #pragma once
 
 /// Returned by popup::show whenever the popup is opened
@@ -9,3 +16,5 @@ namespace imutils
 int popup(const std::string& title, const std::string& question, const std::string* choices, std::size_t num_choices,
     float font_scale = 1.75f);
 } // namespace imutils
+
+#endif
diff --git a/src/game/client/gui/imutils_text.cc b/src/game/client/gui/imutils_text.cc
index 1058c7f..1621c42 100644
--- a/src/game/client/gui/imutils_text.cc
+++ b/src/game/client/gui/imutils_text.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: imutils_text.cc
+// Description: Text with shadow
+
 #include "client/pch.hh"
 
 #include "client/gui/imutils_text.hh"
diff --git a/src/game/client/gui/imutils_text.hh b/src/game/client/gui/imutils_text.hh
index 64d06a4..0d888d4 100644
--- a/src/game/client/gui/imutils_text.hh
+++ b/src/game/client/gui/imutils_text.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: imutils_text.hh
+// Description: Text with shadow
+
+#ifndef CLIENT_GUI_IMUTILS_TEXT_HH
+#define CLIENT_GUI_IMUTILS_TEXT_HH
 #pragma once
 
 namespace imutils
@@ -7,3 +14,5 @@ void text_nw(ImDrawList* list, std::string_view text, const ImVec2& pos, ImU32 c
 void text_wr(ImDrawList* list, std::string_view text, const ImVec2& pos, ImU32 color, ImU32 shadow, ImFont* font, float wrap);
 void text_wr(ImDrawList* list, std::string_view text, const ImVec2& pos, ImU32 color, ImU32 shadow, ImFont* font, float wrap, float size);
 } // namespace imutils
+
+#endif
diff --git a/src/game/client/gui/language.cc b/src/game/client/gui/language.cc
index 8a2d8d1..4ad1f68 100644
--- a/src/game/client/gui/language.cc
+++ b/src/game/client/gui/language.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: language.cc
+// Description: Translations API
+
 #include "client/pch.hh"
 
 #include "client/gui/language.hh"
@@ -41,7 +46,7 @@ void language::init(void)
     auto file = PHYSFS_openRead(std::string(MANIFEST_PATH).c_str());
 
     if(file == nullptr) {
-        spdlog::critical("language: {}: {}", MANIFEST_PATH, physfs_error());
+        spdlog::critical("language: {}: {}", MANIFEST_PATH, physfs::last_error());
         std::terminate();
     }
 
@@ -114,7 +119,7 @@ void language::set(LanguageIterator new_language)
         auto file = PHYSFS_openRead(path.c_str());
 
         if(file == nullptr) {
-            spdlog::warn("language: {}: {}", path, physfs_error());
+            spdlog::warn("language: {}: {}", path, physfs::last_error());
             send_language_event(new_language);
             return;
         }
diff --git a/src/game/client/gui/language.hh b/src/game/client/gui/language.hh
index 20c7520..015e787 100644
--- a/src/game/client/gui/language.hh
+++ b/src/game/client/gui/language.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: language.hh
+// Description: Translations API
+
+#ifndef CLIENT_GUI_LANGUAGE_HH
+#define CLIENT_GUI_LANGUAGE_HH
 #pragma once
 
 struct LanguageInfo final {
@@ -37,3 +44,5 @@ namespace language
 std::string_view resolve(std::string_view key);
 std::string resolve_gui(std::string_view key);
 } // namespace language
+
+#endif
diff --git a/src/game/client/gui/main_menu.cc b/src/game/client/gui/main_menu.cc
index d764449..6fa5cc9 100644
--- a/src/game/client/gui/main_menu.cc
+++ b/src/game/client/gui/main_menu.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: main_menu.cc
+// Description: Main menu screen
+
 #include "client/pch.hh"
 
 #include "client/gui/main_menu.hh"
diff --git a/src/game/client/gui/main_menu.hh b/src/game/client/gui/main_menu.hh
index b5333d4..630a10e 100644
--- a/src/game/client/gui/main_menu.hh
+++ b/src/game/client/gui/main_menu.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: main_menu.hh
+// Description: Main menu screen
+
+#ifndef CLIENT_GUI_MAIN_MENU_HH
+#define CLIENT_GUI_MAIN_MENU_HH
 #pragma once
 
 namespace main_menu
@@ -6,3 +13,5 @@ void init(void);
 void shutdown(void);
 void layout(void);
 } // namespace main_menu
+
+#endif
diff --git a/src/game/client/gui/message_box.cc b/src/game/client/gui/message_box.cc
index d97267a..a97d4e3 100644
--- a/src/game/client/gui/message_box.cc
+++ b/src/game/client/gui/message_box.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: message_box.cc
+// Description: A single message screen
+
 #include "client/pch.hh"
 
 #include "client/gui/message_box.hh"
diff --git a/src/game/client/gui/message_box.hh b/src/game/client/gui/message_box.hh
index 9da5358..430b4fb 100644
--- a/src/game/client/gui/message_box.hh
+++ b/src/game/client/gui/message_box.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: message_box.hh
+// Description: A single message screen
+
+#ifndef CLIENT_GUI_MESSAGE_BOX_HH
+#define CLIENT_GUI_MESSAGE_BOX_HH
 #pragma once
 
 using message_box_action = void (*)(void);
@@ -15,3 +22,5 @@ void set_title(std::string_view title);
 void set_subtitle(std::string_view subtitle);
 void add_button(std::string_view text, const message_box_action& action);
 } // namespace message_box
+
+#endif
diff --git a/src/game/client/gui/metrics.cc b/src/game/client/gui/metrics.cc
index f39434a..0c510d9 100644
--- a/src/game/client/gui/metrics.cc
+++ b/src/game/client/gui/metrics.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: metrics.cc
+// Description: Display debug information
+
 #include "client/pch.hh"
 
 #include "client/gui/metrics.hh"
diff --git a/src/game/client/gui/metrics.hh b/src/game/client/gui/metrics.hh
index ab09c34..441a40d 100644
--- a/src/game/client/gui/metrics.hh
+++ b/src/game/client/gui/metrics.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: metrics.hh
+// Description: Display debug information
+
+#ifndef CLIENT_GUI_METRICS_HH
+#define CLIENT_GUI_METRICS_HH
 #pragma once
 
 namespace metrics
@@ -5,3 +12,5 @@ namespace metrics
 void init(void);
 void layout(void);
 } // namespace metrics
+
+#endif
diff --git a/src/game/client/gui/play_menu.cc b/src/game/client/gui/play_menu.cc
index ec263a7..61a99a4 100644
--- a/src/game/client/gui/play_menu.cc
+++ b/src/game/client/gui/play_menu.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: play_menu.cc
+// Description: Server and world list screen
+
 #include "client/pch.hh"
 
 #include "client/gui/play_menu.hh"
diff --git a/src/game/client/gui/play_menu.hh b/src/game/client/gui/play_menu.hh
index 5069592..eeaeca8 100644
--- a/src/game/client/gui/play_menu.hh
+++ b/src/game/client/gui/play_menu.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: play_menu.hh
+// Description: Server and world list screen
+
+#ifndef CLIENT_GUI_PLAY_MENU_HH
+#define CLIENT_GUI_PLAY_MENU_HH
 #pragma once
 
 namespace play_menu
@@ -7,3 +14,5 @@ void shutdown(void);
 void layout(void);
 void update_late(void);
 } // namespace play_menu
+
+#endif
diff --git a/src/game/client/gui/progress_bar.cc b/src/game/client/gui/progress_bar.cc
index 6cc7fae..6b85efe 100644
--- a/src/game/client/gui/progress_bar.cc
+++ b/src/game/client/gui/progress_bar.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: progress_bar.cc
+// Description: Screen with a progress bar
+
 #include "client/pch.hh"
 
 #include "client/gui/progress_bar.hh"
diff --git a/src/game/client/gui/progress_bar.hh b/src/game/client/gui/progress_bar.hh
index 931cad0..e4569e8 100644
--- a/src/game/client/gui/progress_bar.hh
+++ b/src/game/client/gui/progress_bar.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: progress_bar.hh
+// Description: Screen with a progress bar
+
+#ifndef CLIENT_GUI_PROGRESS_BAR_HH
+#define CLIENT_GUI_PROGRESS_BAR_HH
 #pragma once
 
 using progress_bar_action = void (*)(void);
@@ -14,3 +21,5 @@ void reset(void);
 void set_title(std::string_view title);
 void set_button(std::string_view text, const progress_bar_action& action);
 } // namespace progress_bar
+
+#endif
diff --git a/src/game/client/gui/scoreboard.cc b/src/game/client/gui/scoreboard.cc
index 23f3174..1405119 100644
--- a/src/game/client/gui/scoreboard.cc
+++ b/src/game/client/gui/scoreboard.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: scoreboard.cc
+// Description: Display player list
+
 #include "client/pch.hh"
 
 #include "client/gui/scoreboard.hh"
diff --git a/src/game/client/gui/scoreboard.hh b/src/game/client/gui/scoreboard.hh
index 86f8088..fd4bf32 100644
--- a/src/game/client/gui/scoreboard.hh
+++ b/src/game/client/gui/scoreboard.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: scoreboard.hh
+// Description: Display player list
+
+#ifndef CLIENT_GUI_SCOREBOARD_HH
+#define CLIENT_GUI_SCOREBOARD_HH
 #pragma once
 
 namespace scoreboard
@@ -5,3 +12,5 @@ namespace scoreboard
 void init(void);
 void layout(void);
 } // namespace scoreboard
+
+#endif
diff --git a/src/game/client/gui/settings.cc b/src/game/client/gui/settings.cc
index b456909..65e91aa 100644
--- a/src/game/client/gui/settings.cc
+++ b/src/game/client/gui/settings.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: settings.cc
+// Description: Visual config value editing
+
 #include "client/pch.hh"
 
 #include "client/gui/settings.hh"
diff --git a/src/game/client/gui/settings.hh b/src/game/client/gui/settings.hh
index efb8ca4..1a3a1f8 100644
--- a/src/game/client/gui/settings.hh
+++ b/src/game/client/gui/settings.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: settings.hh
+// Description: Visual config value editing
+
+#ifndef CLIENT_GUI_SETTINGS_HH
+#define CLIENT_GUI_SETTINGS_HH
 #pragma once
 
 namespace config
@@ -88,3 +95,5 @@ namespace settings
 {
 void add_language_select(int priority, settings_location location, std::string_view name);
 } // namespace settings
+
+#endif
diff --git a/src/game/client/gui/splash.cc b/src/game/client/gui/splash.cc
index 84ecb8b..7d7b86c 100644
--- a/src/game/client/gui/splash.cc
+++ b/src/game/client/gui/splash.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: splash.cc
+// Description: Startup splash screen
+
 #include "client/pch.hh"
 
 #include "client/gui/splash.hh"
diff --git a/src/game/client/gui/splash.hh b/src/game/client/gui/splash.hh
index ca612fe..abdeb5a 100644
--- a/src/game/client/gui/splash.hh
+++ b/src/game/client/gui/splash.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: splash.hh
+// Description: Startup splash screen
+
+#ifndef CLIENT_GUI_SPLASH_HH
+#define CLIENT_GUI_SPLASH_HH
 #pragma once
 
 namespace client_splash
@@ -6,3 +13,5 @@ void init(void);
 void init_late(void);
 void render(void);
 } // namespace client_splash
+
+#endif
diff --git a/src/game/client/gui/status_lines.cc b/src/game/client/gui/status_lines.cc
index ce661a3..39421b2 100644
--- a/src/game/client/gui/status_lines.cc
+++ b/src/game/client/gui/status_lines.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: status_lines.cc
+// Description: Display lines of text in-game
+
 #include "client/pch.hh"
 
 #include "client/gui/status_lines.hh"
diff --git a/src/game/client/gui/status_lines.hh b/src/game/client/gui/status_lines.hh
index b921947..706b4ad 100644
--- a/src/game/client/gui/status_lines.hh
+++ b/src/game/client/gui/status_lines.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: status_lines.hh
+// Description: Display lines of text in-game
+
+#ifndef CLIENT_GUI_STATUS_LINES_HH
+#define CLIENT_GUI_STATUS_LINES_HH
 #pragma once
 
 constexpr static unsigned int STATUS_DEBUG = 0x0000;  // generic debug line
@@ -16,3 +23,5 @@ namespace status_lines
 void set(unsigned int line, std::string_view text, const ImVec4& color, float fadeout);
 void unset(unsigned int line);
 } // namespace status_lines
+
+#endif
diff --git a/src/game/client/gui/window_title.cc b/src/game/client/gui/window_title.cc
index b15f2c5..ea65b64 100644
--- a/src/game/client/gui/window_title.cc
+++ b/src/game/client/gui/window_title.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: window_title.cc
+// Description: Random MOTD in the window title
+
 #include "client/pch.hh"
 
 #include "client/gui/window_title.hh"
diff --git a/src/game/client/gui/window_title.hh b/src/game/client/gui/window_title.hh
index 544ed44..78f7326 100644
--- a/src/game/client/gui/window_title.hh
+++ b/src/game/client/gui/window_title.hh
@@ -1,6 +1,15 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: window_title.hh
+// Description: Random MOTD in the window title
+
+#ifndef CLIENT_GUI_WINDOW_TITLE_HH
+#define CLIENT_GUI_WINDOW_TITLE_HH
 #pragma once
 
 namespace window_title
 {
 void update(void);
 } // namespace window_title
+
+#endif
diff --git a/src/game/client/io/gamepad.cc b/src/game/client/io/gamepad.cc
index 2c99107..768b18b 100644
--- a/src/game/client/io/gamepad.cc
+++ b/src/game/client/io/gamepad.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: gamepad.cc
+// Description: Gamepad support
+
 #include "client/pch.hh"
 
 #include "client/io/gamepad.hh"
diff --git a/src/game/client/io/gamepad.hh b/src/game/client/io/gamepad.hh
index 5f76277..b506cc2 100644
--- a/src/game/client/io/gamepad.hh
+++ b/src/game/client/io/gamepad.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: gamepad.hh
+// Description: Gamepad support
+
+#ifndef CLIENT_IO_GAMEPAD_HH
+#define CLIENT_IO_GAMEPAD_HH
 #pragma once
 
 constexpr static int INVALID_GAMEPAD_AXIS = INT_MAX;
@@ -42,3 +49,5 @@ struct GamepadButtonEvent final {
     int action;
     int button;
 };
+
+#endif
diff --git a/src/game/client/io/glfw.hh b/src/game/client/io/glfw.hh
index ad445f9..9da978b 100644
--- a/src/game/client/io/glfw.hh
+++ b/src/game/client/io/glfw.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: glfw.hh
+// Description: GLFW events passed through EnTT's signal system
+
+#ifndef CLIENT_IO_GLFW_HH
+#define CLIENT_IO_GLFW_HH
 #pragma once
 
 struct GlfwCursorPosEvent final {
@@ -31,3 +38,5 @@ struct GlfwScrollEvent final {
     float dx;
     float dy;
 };
+
+#endif
diff --git a/src/game/client/io/sound.cc b/src/game/client/io/sound.cc
index e67c456..886da2c 100644
--- a/src/game/client/io/sound.cc
+++ b/src/game/client/io/sound.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: sound.cc
+// Description: Sound handling
+
 #include "client/pch.hh"
 
 #include "client/io/sound.hh"
diff --git a/src/game/client/io/sound.hh b/src/game/client/io/sound.hh
index d96d0c4..f61410a 100644
--- a/src/game/client/io/sound.hh
+++ b/src/game/client/io/sound.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: sound.hh
+// Description: Sound handling
+
+#ifndef CLIENT_IO_SOUND_HH
+#define CLIENT_IO_SOUND_HH
 #pragma once
 
 #include "core/resource/resource.hh"
@@ -41,3 +48,5 @@ void play_entity(entt::entity entity, resource_ptr<SoundEffect> sound, bool loop
 void play_player(resource_ptr<SoundEffect> sound, bool looping, float pitch);
 void play_ui(resource_ptr<SoundEffect> sound, bool looping, float pitch);
 } // namespace sound
+
+#endif
diff --git a/src/game/client/main.cc b/src/game/client/main.cc
index 32333db..ab45db5 100644
--- a/src/game/client/main.cc
+++ b/src/game/client/main.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: main.cc
+// Description: Entry point
+
 #include "client/pch.hh"
 
 #include "core/io/cmdline.hh"
diff --git a/src/game/client/pch.hh b/src/game/client/pch.hh
index 3832081..b09dce5 100644
--- a/src/game/client/pch.hh
+++ b/src/game/client/pch.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: pch.hh
+// Description: Precompiled header
+
+#ifndef CLIENT_PCH_HH
+#define CLIENT_PCH_HH
 #pragma once
 
 #include <shared/pch.hh>
@@ -26,3 +33,5 @@
 #if defined(__unix__)
 #include <dlfcn.h>
 #endif
+
+#endif
diff --git a/src/game/client/program.cc b/src/game/client/program.cc
index 37cc964..5e7b5fb 100644
--- a/src/game/client/program.cc
+++ b/src/game/client/program.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: program.cc
+// Description: Varied OpenGL shader program
+
 #include "client/pch.hh"
 
 #include "client/program.hh"
@@ -78,7 +83,7 @@ bool GL_Program::setup(std::string_view vpath, std::string_view fpath)
     auto vfile = PHYSFS_openRead(vert_path.c_str());
 
     if(vfile == nullptr) {
-        spdlog::warn("gl_program: {}: {}", vpath, physfs_error());
+        spdlog::warn("gl_program: {}: {}", vpath, physfs::last_error());
         return false;
     }
 
@@ -89,7 +94,7 @@ bool GL_Program::setup(std::string_view vpath, std::string_view fpath)
     auto ffile = PHYSFS_openRead(frag_path.c_str());
 
     if(ffile == nullptr) {
-        spdlog::warn("gl_program: {}: {}", fpath, physfs_error());
+        spdlog::warn("gl_program: {}: {}", fpath, physfs::last_error());
         return false;
     }
 
diff --git a/src/game/client/program.hh b/src/game/client/program.hh
index af78513..6bf69ca 100644
--- a/src/game/client/program.hh
+++ b/src/game/client/program.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: program.hh
+// Description: Varied OpenGL shader program
+
+#ifndef CLIENT_PROGRAM_HH
+#define CLIENT_PROGRAM_HH
 #pragma once
 
 struct GL_VariedMacro final {
@@ -32,3 +39,5 @@ public:
     bool needs_update;
     GLuint handle;
 };
+
+#endif
diff --git a/src/game/client/receive.cc b/src/game/client/receive.cc
index bc7b92e..5331dc5 100644
--- a/src/game/client/receive.cc
+++ b/src/game/client/receive.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: receive.cc
+// Description: Handle incoming packets
+
 #include "client/pch.hh"
 
 #include "client/receive.hh"
diff --git a/src/game/client/receive.hh b/src/game/client/receive.hh
index d675392..9f35488 100644
--- a/src/game/client/receive.hh
+++ b/src/game/client/receive.hh
@@ -1,6 +1,15 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: receive.hh
+// Description: Handle incoming packets
+
+#ifndef CLIENT_RECEIVE_HH
+#define CLIENT_RECEIVE_HH
 #pragma once
 
 namespace client_receive
 {
 void init(void);
 } // namespace client_receive
+
+#endif
diff --git a/src/game/client/resource/sound_effect.cc b/src/game/client/resource/sound_effect.cc
index 4cc5b70..6b87dcc 100644
--- a/src/game/client/resource/sound_effect.cc
+++ b/src/game/client/resource/sound_effect.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: sound_effect.cc
+// Description: Sound effect resource
+
 #include "client/pch.hh"
 
 #include "client/resource/sound_effect.hh"
@@ -35,7 +40,7 @@ static const void* sound_effect_load_func(const char* name, std::uint32_t flags)
     auto file = PHYSFS_openRead(name);
 
     if(file == nullptr) {
-        spdlog::warn("sfx: {}: {}", name, physfs_error());
+        spdlog::warn("sfx: {}: {}", name, physfs::last_error());
         return nullptr;
     }
 
diff --git a/src/game/client/resource/sound_effect.hh b/src/game/client/resource/sound_effect.hh
index f2db33b..602293c 100644
--- a/src/game/client/resource/sound_effect.hh
+++ b/src/game/client/resource/sound_effect.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: sound_effect.hh
+// Description: Sound effect resource
+
+#ifndef CLIENT_RESOURCE_SOUND_EFFECT_HH
+#define CLIENT_RESOURCE_SOUND_EFFECT_HH
 #pragma once
 
 struct SoundEffect final {
@@ -6,3 +13,5 @@ struct SoundEffect final {
     std::string name;
     ALuint buffer;
 };
+
+#endif
diff --git a/src/game/client/resource/texture_gui.cc b/src/game/client/resource/texture_gui.cc
index beb2f54..b87a244 100644
--- a/src/game/client/resource/texture_gui.cc
+++ b/src/game/client/resource/texture_gui.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: texture_gui.cc
+// Description: GUI texture resource
+
 #include "client/pch.hh"
 
 #include "client/resource/texture_gui.hh"
@@ -12,11 +17,11 @@ static const void* texture_gui_load_func(const char* name, std::uint32_t flags)
     unsigned int image_load_flags = 0U;
 
     if(flags & TEXTURE_GUI_LOAD_VFLIP) {
-        image_load_flags |= IMAGE_LOAD_FLIP;
+        image_load_flags |= IMGFLAG_FLIP;
     }
 
     if(flags & TEXTURE_GUI_LOAD_GRAYSCALE) {
-        image_load_flags |= IMAGE_LOAD_GRAY;
+        image_load_flags |= IMGFLAG_GRAY;
     }
 
     if(auto image = resource::load<Image>(name, image_load_flags)) {
diff --git a/src/game/client/resource/texture_gui.hh b/src/game/client/resource/texture_gui.hh
index 2d42c83..2487a77 100644
--- a/src/game/client/resource/texture_gui.hh
+++ b/src/game/client/resource/texture_gui.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: texture_gui.hh
+// Description: GUI texture resource
+
+#ifndef CLIENT_RESOURCE_TEXTURE_GUI_HH
+#define CLIENT_RESOURCE_TEXTURE_GUI_HH
 #pragma once
 
 constexpr static unsigned int TEXTURE_GUI_LOAD_CLAMP_S = 0x0001;
@@ -13,3 +20,5 @@ struct TextureGUI final {
     ImTextureID handle;
     glm::ivec2 size;
 };
+
+#endif
diff --git a/src/game/client/screenshot.cc b/src/game/client/screenshot.cc
index d704f47..a4c043e 100644
--- a/src/game/client/screenshot.cc
+++ b/src/game/client/screenshot.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: screenshot.cc
+// Description: Screenshot handling
+
 #include "client/pch.hh"
 
 #include "client/screenshot.hh"
diff --git a/src/game/client/screenshot.hh b/src/game/client/screenshot.hh
index fecbd2f..17886f9 100644
--- a/src/game/client/screenshot.hh
+++ b/src/game/client/screenshot.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: screenshot.hh
+// Description: Screenshot handling
+
+#ifndef CLIENT_SCREENSHOT_HH
+#define CLIENT_SCREENSHOT_HH
 #pragma once
 
 namespace screenshot
@@ -5,3 +12,5 @@ namespace screenshot
 void init(void);
 void take(void);
 } // namespace screenshot
+
+#endif
diff --git a/src/game/client/session.cc b/src/game/client/session.cc
index 94af475..7c38b28 100644
--- a/src/game/client/session.cc
+++ b/src/game/client/session.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: session.cc
+// Description: Session handling
+
 #include "client/pch.hh"
 
 #include "client/session.hh"
diff --git a/src/game/client/session.hh b/src/game/client/session.hh
index f61d62d..a513974 100644
--- a/src/game/client/session.hh
+++ b/src/game/client/session.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: session.hh
+// Description: Session handling
+
+#ifndef CLIENT_SESSION_HH
+#define CLIENT_SESSION_HH
 #pragma once
 
 namespace session
@@ -25,3 +32,5 @@ namespace session
 {
 bool is_ingame(void);
 } // namespace session
+
+#endif
diff --git a/src/game/client/toggles.cc b/src/game/client/toggles.cc
index 5381993..96f9dfd 100644
--- a/src/game/client/toggles.cc
+++ b/src/game/client/toggles.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: toggles.cc
+// Description: Debug and not-so-debug toggles
+
 #include "client/pch.hh"
 
 #include "client/toggles.hh"
diff --git a/src/game/client/toggles.hh b/src/game/client/toggles.hh
index d051a92..b778ff7 100644
--- a/src/game/client/toggles.hh
+++ b/src/game/client/toggles.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: toggles.hh
+// Description: Debug and not-so-debug toggles
+
+#ifndef CLIENT_TOGGLES_HH
+#define CLIENT_TOGGLES_HH
 #pragma once
 
 using toggle_type = unsigned int;
@@ -33,3 +40,5 @@ void init_late(void);
 bool get(toggle_type type);
 void set(toggle_type type, bool value);
 } // namespace toggles
+
+#endif
diff --git a/src/game/client/world/chunk_mesher.cc b/src/game/client/world/chunk_mesher.cc
index 47ef4cb..a7cf4ee 100644
--- a/src/game/client/world/chunk_mesher.cc
+++ b/src/game/client/world/chunk_mesher.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chunk_mesher.cc
+// Description: Threaded voxel mesh generation
+
 #include "client/pch.hh"
 
 #include "client/world/chunk_mesher.hh"
diff --git a/src/game/client/world/chunk_mesher.hh b/src/game/client/world/chunk_mesher.hh
index d3ead5c..0a4639d 100644
--- a/src/game/client/world/chunk_mesher.hh
+++ b/src/game/client/world/chunk_mesher.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chunk_mesher.hh
+// Description: Threaded voxel mesh generation
+
+#ifndef CLIENT_WORLD_CHUNK_MESHER_HH
+#define CLIENT_WORLD_CHUNK_MESHER_HH
 #pragma once
 
 #include "client/world/chunk_vbo.hh"
@@ -13,3 +20,5 @@ void init(void);
 void shutdown(void);
 void update(void);
 } // namespace chunk_mesher
+
+#endif
diff --git a/src/game/client/world/chunk_quad.hh b/src/game/client/world/chunk_quad.hh
index a28193a..3fc3750 100644
--- a/src/game/client/world/chunk_quad.hh
+++ b/src/game/client/world/chunk_quad.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chunk_quad.hh
+// Description: Packed quad vertex format
+
+#ifndef CLIENT_WORLD_CHUNK_QUAD_HH
+#define CLIENT_WORLD_CHUNK_QUAD_HH
 #pragma once
 
 #include "core/math/constexpr.hh"
@@ -33,3 +40,5 @@ constexpr inline static ChunkQuad make_chunk_quad(const glm::fvec3& position, co
 
     return result;
 }
+
+#endif
diff --git a/src/game/client/world/chunk_renderer.cc b/src/game/client/world/chunk_renderer.cc
index ea85eee..9ea6799 100644
--- a/src/game/client/world/chunk_renderer.cc
+++ b/src/game/client/world/chunk_renderer.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chunk_renderer.cc
+// Description: Chunk mesh rendering
+
 #include "client/pch.hh"
 
 #include "client/world/chunk_renderer.hh"
diff --git a/src/game/client/world/chunk_renderer.hh b/src/game/client/world/chunk_renderer.hh
index 53272a4..ce077cd 100644
--- a/src/game/client/world/chunk_renderer.hh
+++ b/src/game/client/world/chunk_renderer.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chunk_renderer.hh
+// Description: Chunk mesh rendering
+
+#ifndef CLIENT_WORLD_CHUNK_RENDERER_HH
+#define CLIENT_WORLD_CHUNK_RENDERER_HH
 #pragma once
 
 namespace chunk_renderer
@@ -6,3 +13,5 @@ void init(void);
 void shutdown(void);
 void render(void);
 } // namespace chunk_renderer
+
+#endif
diff --git a/src/game/client/world/chunk_vbo.hh b/src/game/client/world/chunk_vbo.hh
index da8270e..e9061d8 100644
--- a/src/game/client/world/chunk_vbo.hh
+++ b/src/game/client/world/chunk_vbo.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chunk_vbo.hh
+// Description: Utility wrapper for OpenGL VBOs
+
+#ifndef CLIENT_WORLD_CHUNK_VBO_HH
+#define CLIENT_WORLD_CHUNK_VBO_HH
 #pragma once
 
 class ChunkVBO final {
@@ -17,3 +24,5 @@ public:
         }
     }
 };
+
+#endif
diff --git a/src/game/client/world/chunk_visibility.cc b/src/game/client/world/chunk_visibility.cc
index 5af2901..407ee69 100644
--- a/src/game/client/world/chunk_visibility.cc
+++ b/src/game/client/world/chunk_visibility.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chunk_visibility.cc
+// Description: Discard chunks out of view
+
 #include "client/pch.hh"
 
 #include "client/world/chunk_visibility.hh"
diff --git a/src/game/client/world/chunk_visibility.hh b/src/game/client/world/chunk_visibility.hh
index d0b4487..a8fcc20 100644
--- a/src/game/client/world/chunk_visibility.hh
+++ b/src/game/client/world/chunk_visibility.hh
@@ -1,6 +1,15 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chunk_visibility.hh
+// Description: Discard chunks out of view
+
+#ifndef CLIENT_WORLD_CHUNK_VISIBILITY_HH
+#define CLIENT_WORLD_CHUNK_VISIBILITY_HH
 #pragma once
 
 namespace chunk_visibility
 {
 void update_late(void);
 } // namespace chunk_visibility
+
+#endif
diff --git a/src/game/client/world/outline.cc b/src/game/client/world/outline.cc
index d4980c2..5e2a7cb 100644
--- a/src/game/client/world/outline.cc
+++ b/src/game/client/world/outline.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: outline.cc
+// Description: Debug-esque line rendering
+
 #include "client/pch.hh"
 
 #include "client/world/outline.hh"
diff --git a/src/game/client/world/outline.hh b/src/game/client/world/outline.hh
index 8fdfdeb..e2e2dfb 100644
--- a/src/game/client/world/outline.hh
+++ b/src/game/client/world/outline.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: outline.hh
+// Description: Debug-esque line rendering
+
+#ifndef CLIENT_WORLD_OUTLINE_HH
+#define CLIENT_WORLD_OUTLINE_HH
 #pragma once
 
 #include "shared/types.hh"
@@ -14,3 +21,5 @@ namespace outline
 void cube(const chunk_pos& cpos, const glm::fvec3& fpos, const glm::fvec3& size, float thickness, const glm::fvec4& color);
 void line(const chunk_pos& cpos, const glm::fvec3& fpos, const glm::fvec3& size, float thickness, const glm::fvec4& color);
 } // namespace outline
+
+#endif
diff --git a/src/game/client/world/player_target.cc b/src/game/client/world/player_target.cc
index c8a7583..b1be8e7 100644
--- a/src/game/client/world/player_target.cc
+++ b/src/game/client/world/player_target.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: player_target.cc
+// Description: Handle logic for targeting voxels
+
 #include "client/pch.hh"
 
 #include "client/world/player_target.hh"
diff --git a/src/game/client/world/player_target.hh b/src/game/client/world/player_target.hh
index 2c8bd22..f160bb3 100644
--- a/src/game/client/world/player_target.hh
+++ b/src/game/client/world/player_target.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: player_target.hh
+// Description: Handle logic for targeting voxels
+
+#ifndef CLIENT_WORLD_PLAYER_TARGET_HH
+#define CLIENT_WORLD_PLAYER_TARGET_HH
 #pragma once
 
 #include "shared/world/voxel_registry.hh"
@@ -15,3 +22,5 @@ void init(void);
 void update(void);
 void render(void);
 } // namespace player_target
+
+#endif
diff --git a/src/game/client/world/skybox.cc b/src/game/client/world/skybox.cc
index 393c260..8c97dc6 100644
--- a/src/game/client/world/skybox.cc
+++ b/src/game/client/world/skybox.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: skybox.cc
+// Description: Skybox rendering
+
 #include "client/pch.hh"
 
 #include "client/world/skybox.hh"
diff --git a/src/game/client/world/skybox.hh b/src/game/client/world/skybox.hh
index d90336a..421b891 100644
--- a/src/game/client/world/skybox.hh
+++ b/src/game/client/world/skybox.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: skybox.hh
+// Description: Skybox rendering
+
+#ifndef CLIENT_WORLD_SKYBOX_HH
+#define CLIENT_WORLD_SKYBOX_HH
 #pragma once
 
 namespace skybox
@@ -9,3 +16,5 @@ namespace skybox
 {
 void init(void);
 } // namespace skybox
+
+#endif
diff --git a/src/game/client/world/voxel_anims.cc b/src/game/client/world/voxel_anims.cc
index 2286027..6af5eaa 100644
--- a/src/game/client/world/voxel_anims.cc
+++ b/src/game/client/world/voxel_anims.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: voxel_anims.cc
+// Description: Voxel texture animations framerate control
+
 #include "client/pch.hh"
 
 #include "client/world/voxel_anims.hh"
diff --git a/src/game/client/world/voxel_anims.hh b/src/game/client/world/voxel_anims.hh
index 63a4fc1..76df53d 100644
--- a/src/game/client/world/voxel_anims.hh
+++ b/src/game/client/world/voxel_anims.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: voxel_anims.hh
+// Description: Voxel texture animations framerate control
+
+#ifndef CLIENT_WORLD_VOXEL_ANIMS_HH
+#define CLIENT_WORLD_VOXEL_ANIMS_HH
 #pragma once
 
 namespace voxel_anims
@@ -11,3 +18,5 @@ namespace voxel_anims
 void init(void);
 void update(void);
 } // namespace voxel_anims
+
+#endif
diff --git a/src/game/client/world/voxel_atlas.cc b/src/game/client/world/voxel_atlas.cc
index 9762998..ee3bca7 100644
--- a/src/game/client/world/voxel_atlas.cc
+++ b/src/game/client/world/voxel_atlas.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: voxel_atlas.cc
+// Description: Multi-array-texture that acts like a spritesheet
+
 #include "client/pch.hh"
 
 #include "client/world/voxel_atlas.hh"
@@ -66,7 +71,7 @@ static AtlasStrip* plane_new_strip(AtlasPlane& plane, const std::vector<std::str
     glBindTexture(GL_TEXTURE_2D_ARRAY, plane.gl_texture);
 
     for(std::size_t i = 0; i < paths.size(); ++i) {
-        if(auto image = resource::load<Image>(paths[i].c_str(), IMAGE_LOAD_FLIP)) {
+        if(auto image = resource::load<Image>(paths[i].c_str(), IMGFLAG_FLIP)) {
             if((image->size.x != atlas_width) || (image->size.y != atlas_height)) {
                 spdlog::warn("atlas: {}: size mismatch", paths[i]);
                 continue;
diff --git a/src/game/client/world/voxel_atlas.hh b/src/game/client/world/voxel_atlas.hh
index acfcfbd..ae04d7b 100644
--- a/src/game/client/world/voxel_atlas.hh
+++ b/src/game/client/world/voxel_atlas.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: voxel_atlas.hh
+// Description: Multi-array-texture that acts like a spritesheet
+
+#ifndef CLIENT_WORLD_VOXEL_ATLAS_HH
+#define CLIENT_WORLD_VOXEL_ATLAS_HH
 #pragma once
 
 struct AtlasStrip final {
@@ -23,3 +30,5 @@ namespace voxel_atlas
 AtlasStrip* find_or_load(const std::vector<std::string>& paths);
 AtlasStrip* find(const std::vector<std::string>& paths);
 } // namespace voxel_atlas
+
+#endif
diff --git a/src/game/client/world/voxel_sounds.cc b/src/game/client/world/voxel_sounds.cc
index b60df94..86aa8ee 100644
--- a/src/game/client/world/voxel_sounds.cc
+++ b/src/game/client/world/voxel_sounds.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: voxel_sounds.cc
+// Description: Handle voxel sounds
+
 #include "client/pch.hh"
 
 #include "client/world/voxel_sounds.hh"
diff --git a/src/game/client/world/voxel_sounds.hh b/src/game/client/world/voxel_sounds.hh
index 1b14698..1ed57e2 100644
--- a/src/game/client/world/voxel_sounds.hh
+++ b/src/game/client/world/voxel_sounds.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: voxel_sounds.hh
+// Description: Handle voxel sounds
+
+#ifndef CLIENT_WORLD_VOXEL_SOUNDS_HH
+#define CLIENT_WORLD_VOXEL_SOUNDS_HH
 #pragma once
 
 #include "core/resource/resource.hh"
@@ -17,3 +24,5 @@ namespace voxel_sounds
 resource_ptr<SoundEffect> get_footsteps(VoxelMaterial material);
 resource_ptr<SoundEffect> get_placebreak(VoxelMaterial material);
 } // namespace voxel_sounds
+
+#endif
diff --git a/src/game/server/chat.cc b/src/game/server/chat.cc
index a0ceba8..5bb2258 100644
--- a/src/game/server/chat.cc
+++ b/src/game/server/chat.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chat.cc
+// Description: Chat handling
+
 #include "server/pch.hh"
 
 #include "server/chat.hh"
diff --git a/src/game/server/chat.hh b/src/game/server/chat.hh
index 1b3e11b..671fd22 100644
--- a/src/game/server/chat.hh
+++ b/src/game/server/chat.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chat.hh
+// Description: Chat handling
+
+#ifndef SERVER_CHAT_HH
+#define SERVER_CHAT_HH
 #pragma once
 
 struct Session;
@@ -10,3 +17,5 @@ void broadcast(std::string_view message, std::string_view sender);
 void send(Session* session, std::string_view message);
 void send(Session* session, std::string_view message, std::string_view sender);
 } // namespace server_chat
+
+#endif
diff --git a/src/game/server/game.cc b/src/game/server/game.cc
index deb7d68..0aa976e 100644
--- a/src/game/server/game.cc
+++ b/src/game/server/game.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: game.cc
+// Description: Main game logic
+
 #include "server/pch.hh"
 
 #include "server/game.hh"
diff --git a/src/game/server/game.hh b/src/game/server/game.hh
index 1dbe4b8..dccd2f5 100644
--- a/src/game/server/game.hh
+++ b/src/game/server/game.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: game.hh
+// Description: Main game logic
+
+#ifndef SERVER_GAME_HH
+#define SERVER_GAME_HH
 #pragma once
 
 namespace config
@@ -23,3 +30,5 @@ void shutdown(void);
 void fixed_update(void);
 void fixed_update_late(void);
 } // namespace server_game
+
+#endif
diff --git a/src/game/server/globals.cc b/src/game/server/globals.cc
index 12fce4a..796d9f2 100644
--- a/src/game/server/globals.cc
+++ b/src/game/server/globals.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: globals.cc
+// Description: Global variables
+
 #include "server/pch.hh"
 
 #include "server/globals.hh"
diff --git a/src/game/server/globals.hh b/src/game/server/globals.hh
index 80e84bb..c44b03a 100644
--- a/src/game/server/globals.hh
+++ b/src/game/server/globals.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: globals.hh
+// Description: Global variables
+
+#ifndef SERVER_GLOBALS_HH
+#define SERVER_GLOBALS_HH
 #pragma once
 
 #include "shared/globals.hh"
@@ -19,3 +26,5 @@ extern std::uint64_t tickrate_dt;
 extern Dimension* spawn_dimension;
 extern std::unordered_map<std::string, Dimension*> dimensions;
 } // namespace globals
+
+#endif
diff --git a/src/game/server/main.cc b/src/game/server/main.cc
index 181145f..7c70ae1 100644
--- a/src/game/server/main.cc
+++ b/src/game/server/main.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: main.cc
+// Description: Entry point
+
 #include "server/pch.hh"
 
 #include "core/config/number.hh"
diff --git a/src/game/server/pch.hh b/src/game/server/pch.hh
index 6f42c17..a7892d8 100644
--- a/src/game/server/pch.hh
+++ b/src/game/server/pch.hh
@@ -1,3 +1,12 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: pch.hh
+// Description: Precompiled header
+
+#ifndef SERVER_PCH_HH
+#define SERVER_PCH_HH
 #pragma once
 
 #include <shared/pch.hh>
+
+#endif
diff --git a/src/game/server/receive.cc b/src/game/server/receive.cc
index a3ce14b..b9a0da0 100644
--- a/src/game/server/receive.cc
+++ b/src/game/server/receive.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: receive.cc
+// Description: Handle incoming packets
+
 #include "server/pch.hh"
 
 #include "server/receive.hh"
diff --git a/src/game/server/receive.hh b/src/game/server/receive.hh
index 4150226..99c5688 100644
--- a/src/game/server/receive.hh
+++ b/src/game/server/receive.hh
@@ -1,6 +1,15 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: receive.hh
+// Description: Handle incoming packets
+
+#ifndef SERVER_RECEIVE_HH
+#define SERVER_RECEIVE_HH
 #pragma once
 
 namespace server_recieve
 {
 void init(void);
 } // namespace server_recieve
+
+#endif
diff --git a/src/game/server/sessions.cc b/src/game/server/sessions.cc
index b161d55..f66dfa1 100644
--- a/src/game/server/sessions.cc
+++ b/src/game/server/sessions.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: sessions.cc
+// Description: Session handling
+
 #include "server/pch.hh"
 
 #include "server/sessions.hh"
diff --git a/src/game/server/sessions.hh b/src/game/server/sessions.hh
index 4c64f80..7806d71 100644
--- a/src/game/server/sessions.hh
+++ b/src/game/server/sessions.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: sessions.hh
+// Description: Session handling
+
+#ifndef SERVER_SESSIONS_HH
+#define SERVER_SESSIONS_HH
 #pragma once
 
 class Dimension;
@@ -50,3 +57,5 @@ namespace sessions
 {
 void refresh_scoreboard(void);
 } // namespace sessions
+
+#endif
diff --git a/src/game/server/status.cc b/src/game/server/status.cc
index 9414a76..592c5ce 100644
--- a/src/game/server/status.cc
+++ b/src/game/server/status.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: status.cc
+// Description: Respond to client bothering
+
 #include "server/pch.hh"
 
 #include "server/status.hh"
diff --git a/src/game/server/status.hh b/src/game/server/status.hh
index 35370a0..70eea40 100644
--- a/src/game/server/status.hh
+++ b/src/game/server/status.hh
@@ -1,6 +1,15 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: status.hh
+// Description: Respond to client bothering
+
+#ifndef SERVER_STATUS_HH
+#define SERVER_STATUS_HH
 #pragma once
 
 namespace status
 {
 void init(void);
 } // namespace status
+
+#endif
diff --git a/src/game/server/whitelist.cc b/src/game/server/whitelist.cc
index 555e5f3..2370c67 100644
--- a/src/game/server/whitelist.cc
+++ b/src/game/server/whitelist.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: whitelist.cc
+// Description: Player allow-list
+
 #include "server/pch.hh"
 
 #include "server/whitelist.hh"
@@ -48,7 +53,7 @@ void whitelist::init_late(void)
     PHYSFS_File* file = PHYSFS_openRead(whitelist::filename.c_str());
 
     if(file == nullptr) {
-        spdlog::warn("whitelist: {}: {}", whitelist::filename.get(), physfs_error());
+        spdlog::warn("whitelist: {}: {}", whitelist::filename.get(), physfs::last_error());
         whitelist::enabled.set_value(false);
         return;
     }
diff --git a/src/game/server/whitelist.hh b/src/game/server/whitelist.hh
index 4695d16..e9dc3aa 100644
--- a/src/game/server/whitelist.hh
+++ b/src/game/server/whitelist.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: whitelist.hh
+// Description: Player allow-list
+
+#ifndef SERVER_WHITELIST_HH
+#define SERVER_WHITELIST_HH
 #pragma once
 
 namespace config
@@ -24,3 +31,5 @@ namespace whitelist
 bool contains(std::string_view username);
 bool matches(std::string_view username, std::uint64_t password_hash);
 } // namespace whitelist
+
+#endif
diff --git a/src/game/server/world/inhabited.hh b/src/game/server/world/inhabited.hh
index e4b2344..fa34eb2 100644
--- a/src/game/server/world/inhabited.hh
+++ b/src/game/server/world/inhabited.hh
@@ -1,3 +1,12 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: inhabited.hh
+// Description: Flag component for chunks that should be saved on disk
+
+#ifndef SERVER_WORLD_INHABITED_HH
+#define SERVER_WORLD_INHABITED_HH
 #pragma once
 
 struct Inhabited final {};
+
+#endif
diff --git a/src/game/server/world/overworld.cc b/src/game/server/world/overworld.cc
index b03311d..3e9f15b 100644
--- a/src/game/server/world/overworld.cc
+++ b/src/game/server/world/overworld.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: overworld.cc
+// Description: Generic world dimension
+
 #include "server/pch.hh"
 
 #include "server/world/overworld.hh"
diff --git a/src/game/server/world/overworld.hh b/src/game/server/world/overworld.hh
index ef4bb54..fd21089 100644
--- a/src/game/server/world/overworld.hh
+++ b/src/game/server/world/overworld.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: overworld.hh
+// Description: Generic world dimension
+
+#ifndef SERVER_WORLD_OVERWORLD_HH
+#define SERVER_WORLD_OVERWORLD_HH
 #pragma once
 
 #include "core/config/number.hh"
@@ -60,3 +67,5 @@ private:
 private:
     std::mutex m_mutex;
 };
+
+#endif
diff --git a/src/game/server/world/random_tick.cc b/src/game/server/world/random_tick.cc
index 8fdcfeb..6e6c65a 100644
--- a/src/game/server/world/random_tick.cc
+++ b/src/game/server/world/random_tick.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: random_tick.cc
+// Description: Voxel random ticking
+
 #include "server/pch.hh"
 
 #include "server/world/random_tick.hh"
diff --git a/src/game/server/world/random_tick.hh b/src/game/server/world/random_tick.hh
index 9c67dc4..0d01267 100644
--- a/src/game/server/world/random_tick.hh
+++ b/src/game/server/world/random_tick.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: random_tick.hh
+// Description: Voxel random ticking
+
+#ifndef SERVER_WORLD_RANDOM_TICK_HH
+#define SERVER_WORLD_RANDOM_TICK_HH
 #pragma once
 
 #include "shared/types.hh"
@@ -9,3 +16,5 @@ namespace random_tick
 void init(void);
 void tick(const chunk_pos& cpos, Chunk* chunk);
 } // namespace random_tick
+
+#endif
diff --git a/src/game/server/world/universe.cc b/src/game/server/world/universe.cc
index defefc6..0a8d956 100644
--- a/src/game/server/world/universe.cc
+++ b/src/game/server/world/universe.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: universe.cc
+// Description: Dimension handling
+
 #include "server/pch.hh"
 
 #include "server/world/universe.hh"
@@ -52,7 +57,7 @@ static void add_new_dimension(Dimension* dimension)
     auto dimension_dir = std::format("{}/{}", universe_name.get(), dimension->get_name());
 
     if(!PHYSFS_mkdir(dimension_dir.c_str())) {
-        spdlog::critical("universe: {}: {}", dimension_dir, physfs_error());
+        spdlog::critical("universe: {}: {}", dimension_dir, physfs::last_error());
         std::terminate();
     }
 
@@ -61,7 +66,7 @@ static void add_new_dimension(Dimension* dimension)
     metadata->zvox_dir = std::format("{}/chunk", dimension_dir);
 
     if(!PHYSFS_mkdir(metadata->zvox_dir.c_str())) {
-        spdlog::critical("universe: {}: {}", metadata->zvox_dir, physfs_error());
+        spdlog::critical("universe: {}: {}", metadata->zvox_dir, physfs::last_error());
         std::terminate();
     }
 
@@ -109,7 +114,7 @@ void universe::init_late(void)
     const auto universe_dir = std::string(universe_name.get());
 
     if(!PHYSFS_mkdir(universe_dir.c_str())) {
-        spdlog::critical("universe: {}: {}", universe_dir, physfs_error());
+        spdlog::critical("universe: {}: {}", universe_dir, physfs::last_error());
         std::terminate();
     }
 
diff --git a/src/game/server/world/universe.hh b/src/game/server/world/universe.hh
index 31d3721..0901b9e 100644
--- a/src/game/server/world/universe.hh
+++ b/src/game/server/world/universe.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: universe.hh
+// Description: Dimension handling
+
+#ifndef SERVER_WORLD_UNIVERSE_HH
+#define SERVER_WORLD_UNIVERSE_HH
 #pragma once
 
 #include "shared/types.hh"
@@ -20,3 +27,5 @@ Chunk* load_chunk(Dimension* dimension, const chunk_pos& cpos);
 void save_chunk(Dimension* dimension, const chunk_pos& cpos);
 void save_all_chunks(Dimension* dimension);
 } // namespace universe
+
+#endif
diff --git a/src/game/server/world/unloader.cc b/src/game/server/world/unloader.cc
index 5842b14..bbb87d3 100644
--- a/src/game/server/world/unloader.cc
+++ b/src/game/server/world/unloader.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: unloader.cc
+// Description: Handle chunks that are out of view for all players
+
 #include "server/pch.hh"
 
 #include "server/world/unloader.hh"
diff --git a/src/game/server/world/unloader.hh b/src/game/server/world/unloader.hh
index bf816bd..85e7d5e 100644
--- a/src/game/server/world/unloader.hh
+++ b/src/game/server/world/unloader.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: unloader.hh
+// Description: Handle chunks that are out of view for all players
+
+#ifndef SERVER_WORLD_UNLOADER_HH
+#define SERVER_WORLD_UNLOADER_HH
 #pragma once
 
 class Dimension;
@@ -8,3 +15,5 @@ void init(void);
 void init_late(void);
 void fixed_update_late(Dimension* dimension);
 } // namespace unloader
+
+#endif
diff --git a/src/game/server/world/worldgen.cc b/src/game/server/world/worldgen.cc
index c8c7ade..e543208 100644
--- a/src/game/server/world/worldgen.cc
+++ b/src/game/server/world/worldgen.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: worldgen.cc
+// Description: Threaded requests for dimensions to generate chunks
+
 #include "server/pch.hh"
 
 #include "server/world/worldgen.hh"
diff --git a/src/game/server/world/worldgen.hh b/src/game/server/world/worldgen.hh
index f991744..ef0cc49 100644
--- a/src/game/server/world/worldgen.hh
+++ b/src/game/server/world/worldgen.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: worldgen.hh
+// Description: Threaded requests for dimensions to generate chunks
+
+#ifndef SERVER_WORLD_WORLDGEN_HH
+#define SERVER_WORLD_WORLDGEN_HH
 #pragma once
 
 #include "shared/types.hh"
@@ -16,3 +23,5 @@ namespace worldgen
 bool is_generating(Dimension* dimension, const chunk_pos& cpos);
 void request_chunk(Session* session, const chunk_pos& cpos);
 } // namespace worldgen
+
+#endif
diff --git a/src/game/shared/const.hh b/src/game/shared/const.hh
index 187962a..45e1731 100644
--- a/src/game/shared/const.hh
+++ b/src/game/shared/const.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: const.hh
+// Description: Constants
+
+#ifndef SHARED_CONST_HH
+#define SHARED_CONST_HH
 #pragma once
 
 #include "core/math/constexpr.hh"
@@ -41,3 +48,5 @@ constexpr static glm::vec<2, T> ZERO_VEC2 = glm::vec<2, T>(0, 0);
 
 template<typename T>
 constexpr static glm::vec<3, T> ZERO_VEC3 = glm::vec<3, T>(0, 0, 0);
+
+#endif
diff --git a/src/game/shared/coord.hh b/src/game/shared/coord.hh
index 9d9be18..bd66c9b 100644
--- a/src/game/shared/coord.hh
+++ b/src/game/shared/coord.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: coord.hh
+// Description: Coordinate domain change functions
+
+#ifndef SHARED_COORD_HH
+#define SHARED_COORD_HH
 #pragma once
 
 #include "shared/const.hh"
@@ -143,3 +150,5 @@ inline constexpr glm::fvec3 coord::to_fvec3(const chunk_pos& cpos, const glm::fv
         fpos.z + static_cast<float>(cpos.z << CHUNK_BITSHIFT),
     };
 }
+
+#endif
diff --git a/src/game/shared/entity/collision.cc b/src/game/shared/entity/collision.cc
index 322bb91..6878958 100644
--- a/src/game/shared/entity/collision.cc
+++ b/src/game/shared/entity/collision.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: collision.cc
+// Description: Collision detection
+
 #include "shared/pch.hh"
 
 #include "shared/entity/collision.hh"
diff --git a/src/game/shared/entity/collision.hh b/src/game/shared/entity/collision.hh
index 34a648c..89d9756 100644
--- a/src/game/shared/entity/collision.hh
+++ b/src/game/shared/entity/collision.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: collision.hh
+// Description: Collision detection
+
+#ifndef SHARED_ENTITY_COLLISION_HH
+#define SHARED_ENTITY_COLLISION_HH
 #pragma once
 
 #include "core/math/aabb.hh"
@@ -13,3 +20,5 @@ public:
     // because both transform and velocity may be updated internally
     static void fixed_update(Dimension* dimension);
 };
+
+#endif
diff --git a/src/game/shared/entity/factory.cc b/src/game/shared/entity/factory.cc
index f2031df..223e593 100644
--- a/src/game/shared/entity/factory.cc
+++ b/src/game/shared/entity/factory.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: factory.cc
+// Description: Boilerplate entity creation
+
 #include "shared/pch.hh"
 
 #include "shared/entity/factory.hh"
diff --git a/src/game/shared/entity/factory.hh b/src/game/shared/entity/factory.hh
index 7c94136..158b187 100644
--- a/src/game/shared/entity/factory.hh
+++ b/src/game/shared/entity/factory.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: factory.hh
+// Description: Boilerplate entity creation
+
+#ifndef SHARED_ENTITY_FACTORY_HH
+#define SHARED_ENTITY_FACTORY_HH
 #pragma once
 
 class Dimension;
@@ -6,3 +13,5 @@ namespace shared
 {
 void create_player(Dimension* dimension, entt::entity entity);
 } // namespace shared
+
+#endif
diff --git a/src/game/shared/entity/gravity.cc b/src/game/shared/entity/gravity.cc
index 6a5145f..893e819 100644
--- a/src/game/shared/entity/gravity.cc
+++ b/src/game/shared/entity/gravity.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: gravity.cc
+// Description: Gravity component
+
 #include "shared/pch.hh"
 
 #include "shared/entity/gravity.hh"
diff --git a/src/game/shared/entity/gravity.hh b/src/game/shared/entity/gravity.hh
index 38b3c9b..c6ad701 100644
--- a/src/game/shared/entity/gravity.hh
+++ b/src/game/shared/entity/gravity.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: gravity.hh
+// Description: Gravity component
+
+#ifndef SHARED_ENTITY_GRAVITY_HH
+#define SHARED_ENTITY_GRAVITY_HH
 #pragma once
 
 class Dimension;
@@ -6,3 +13,5 @@ struct Gravity final {
 public:
     static void fixed_update(Dimension* dimension);
 };
+
+#endif
diff --git a/src/game/shared/entity/grounded.hh b/src/game/shared/entity/grounded.hh
index 7307e79..38367ec 100644
--- a/src/game/shared/entity/grounded.hh
+++ b/src/game/shared/entity/grounded.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: grounded.hh
+// Description: Flag components for entites that rest on the ground
+
+#ifndef SHARED_ENTITY_GROUNDED_HH
+#define SHARED_ENTITY_GROUNDED_HH
 #pragma once
 
 #include "shared/world/voxel.hh"
@@ -7,3 +14,5 @@
 struct Grounded final {
     VoxelMaterial surface;
 };
+
+#endif
diff --git a/src/game/shared/entity/head.hh b/src/game/shared/entity/head.hh
index 9fa71d9..cec3be4 100644
--- a/src/game/shared/entity/head.hh
+++ b/src/game/shared/entity/head.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: head.hh
+// Description: Head component
+
+#ifndef SHARED_ENTITY_HEAD_HH
+#define SHARED_ENTITY_HEAD_HH
 #pragma once
 
 struct Head {
@@ -11,3 +18,5 @@ namespace client
 struct HeadIntr final : public Head {};
 struct HeadPrev final : public Head {};
 } // namespace client
+
+#endif
diff --git a/src/game/shared/entity/player.hh b/src/game/shared/entity/player.hh
index d7cd020..8edba5e 100644
--- a/src/game/shared/entity/player.hh
+++ b/src/game/shared/entity/player.hh
@@ -1,3 +1,12 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: player.hh
+// Description: Flag components for entites that are players
+
+#ifndef SHARED_ENTITY_PLAYER_HH
+#define SHARED_ENTITY_PLAYER_HH
 #pragma once
 
 struct Player final {};
+
+#endif
diff --git a/src/game/shared/entity/stasis.cc b/src/game/shared/entity/stasis.cc
index 0b8a0c8..72f7592 100644
--- a/src/game/shared/entity/stasis.cc
+++ b/src/game/shared/entity/stasis.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: stasis.cc
+// Description: Freeze entites that are in an unloaded chunk
+
 #include "shared/pch.hh"
 
 #include "shared/entity/stasis.hh"
diff --git a/src/game/shared/entity/stasis.hh b/src/game/shared/entity/stasis.hh
index 5adc592..dfb97b3 100644
--- a/src/game/shared/entity/stasis.hh
+++ b/src/game/shared/entity/stasis.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: stasis.hh
+// Description: Freeze entites that are in an unloaded chunk
+
+#ifndef SHARED_ENTITY_STASIS_HH
+#define SHARED_ENTITY_STASIS_HH
 #pragma once
 
 class Dimension;
@@ -8,3 +15,5 @@ struct Stasis final {
 public:
     static void fixed_update(Dimension* dimension);
 };
+
+#endif
diff --git a/src/game/shared/entity/transform.cc b/src/game/shared/entity/transform.cc
index cf09e2f..2ceee0d 100644
--- a/src/game/shared/entity/transform.cc
+++ b/src/game/shared/entity/transform.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: transform.cc
+// Description: Transform component
+
 #include "shared/pch.hh"
 
 #include "shared/entity/transform.hh"
diff --git a/src/game/shared/entity/transform.hh b/src/game/shared/entity/transform.hh
index afbe9fa..55a00ac 100644
--- a/src/game/shared/entity/transform.hh
+++ b/src/game/shared/entity/transform.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: transform.hh
+// Description: Transform component
+
+#ifndef SHARED_ENTITY_TRANSFORM_HH
+#define SHARED_ENTITY_TRANSFORM_HH
 #pragma once
 
 #include "shared/types.hh"
@@ -22,3 +29,5 @@ namespace client
 struct TransformIntr final : public Transform {};
 struct TransformPrev final : public Transform {};
 } // namespace client
+
+#endif
diff --git a/src/game/shared/entity/velocity.cc b/src/game/shared/entity/velocity.cc
index 6fb8c80..c08b749 100644
--- a/src/game/shared/entity/velocity.cc
+++ b/src/game/shared/entity/velocity.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: velocity.cc
+// Description: Velocity component
+
 #include "shared/pch.hh"
 
 #include "shared/entity/velocity.hh"
diff --git a/src/game/shared/entity/velocity.hh b/src/game/shared/entity/velocity.hh
index 0266bd0..8dccf09 100644
--- a/src/game/shared/entity/velocity.hh
+++ b/src/game/shared/entity/velocity.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: velocity.hh
+// Description: Velocity component
+
+#ifndef SHARED_ENTITY_VELOCITY_HH
+#define SHARED_ENTITY_VELOCITY_HH
 #pragma once
 
 class Dimension;
@@ -18,3 +25,5 @@ namespace client
 struct VelocityIntr final : public Velocity {};
 struct VelocityPrev final : public Velocity {};
 } // namespace client
+
+#endif
diff --git a/src/game/shared/game.cc b/src/game/shared/game.cc
index e839e6a..bac92fb 100644
--- a/src/game/shared/game.cc
+++ b/src/game/shared/game.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: game.cc
+// Description: Shared initialization logic
+
 #include "shared/pch.hh"
 
 #include "shared/game.hh"
@@ -81,7 +86,7 @@ void shared_game::init(int argc, char** argv, std::string_view logfile)
     logger->flush();
 
     if(!PHYSFS_init(argv[0])) {
-        spdlog::critical("physfs: init failed: {}", physfs_error());
+        spdlog::critical("physfs: init failed: {}", physfs::last_error());
         std::terminate();
     }
 
@@ -96,17 +101,17 @@ void shared_game::init(int argc, char** argv, std::string_view logfile)
     std::filesystem::create_directories(userpath, ignore_error);
 
     if(!PHYSFS_mount(gamepath.string().c_str(), nullptr, false)) {
-        spdlog::critical("physfs: mount {} failed: {}", gamepath.string(), physfs_error());
+        spdlog::critical("physfs: mount {} failed: {}", gamepath.string(), physfs::last_error());
         std::terminate();
     }
 
     if(!PHYSFS_mount(userpath.string().c_str(), nullptr, false)) {
-        spdlog::critical("physfs: mount {} failed: {}", userpath.string(), physfs_error());
+        spdlog::critical("physfs: mount {} failed: {}", userpath.string(), physfs::last_error());
         std::terminate();
     }
 
     if(!PHYSFS_setWriteDir(userpath.string().c_str())) {
-        spdlog::critical("physfs: setwritedir {} failed: {}", userpath.string(), physfs_error());
+        spdlog::critical("physfs: setwritedir {} failed: {}", userpath.string(), physfs::last_error());
         std::terminate();
     }
 
@@ -121,7 +126,7 @@ void shared_game::shutdown(void)
     enet_deinitialize();
 
     if(!PHYSFS_deinit()) {
-        spdlog::critical("physfs: deinit failed: {}", physfs_error());
+        spdlog::critical("physfs: deinit failed: {}", physfs::last_error());
         std::terminate();
     }
 }
diff --git a/src/game/shared/game.hh b/src/game/shared/game.hh
index 6e89a3c..8fe3c90 100644
--- a/src/game/shared/game.hh
+++ b/src/game/shared/game.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: game.hh
+// Description: Shared initialization logic
+
+#ifndef SHARED_GAME_HH
+#define SHARED_GAME_HH
 #pragma once
 
 namespace shared_game
@@ -5,3 +12,5 @@ namespace shared_game
 void init(int argc, char** argv, std::string_view logfile = {});
 void shutdown(void);
 } // namespace shared_game
+
+#endif
diff --git a/src/game/shared/game_items.cc b/src/game/shared/game_items.cc
index 73f7cef..5fe8ba3 100644
--- a/src/game/shared/game_items.cc
+++ b/src/game/shared/game_items.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: game_items.cc
+// Description: All the items in the game
+
 #include "shared/pch.hh"
 
 #include "shared/game_items.hh"
diff --git a/src/game/shared/game_items.hh b/src/game/shared/game_items.hh
index 1170543..9901e18 100644
--- a/src/game/shared/game_items.hh
+++ b/src/game/shared/game_items.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: game_items.hh
+// Description: All the items in the game
+
+#ifndef SHARED_GAME_ITEMS_HH
+#define SHARED_GAME_ITEMS_HH
 #pragma once
 
 class Item;
@@ -19,3 +26,5 @@ namespace game_items
 {
 void populate(void);
 } // namespace game_items
+
+#endif
diff --git a/src/game/shared/game_voxels.cc b/src/game/shared/game_voxels.cc
index 010053a..6682dd8 100644
--- a/src/game/shared/game_voxels.cc
+++ b/src/game/shared/game_voxels.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: game_voxels.cc
+// Description: All the voxels in the game
+
 #include "shared/pch.hh"
 
 #include "shared/game_voxels.hh"
diff --git a/src/game/shared/game_voxels.hh b/src/game/shared/game_voxels.hh
index f46385c..403ee86 100644
--- a/src/game/shared/game_voxels.hh
+++ b/src/game/shared/game_voxels.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: game_voxels.hh
+// Description: All the voxels in the game
+
+#ifndef SHARED_GAME_VOXELS_HH
+#define SHARED_GAME_VOXELS_HH
 #pragma once
 
 class Voxel;
@@ -21,3 +28,5 @@ namespace game_voxels
 {
 void populate(void);
 } // namespace game_voxels
+
+#endif
diff --git a/src/game/shared/globals.cc b/src/game/shared/globals.cc
index 8552214..92da492 100644
--- a/src/game/shared/globals.cc
+++ b/src/game/shared/globals.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: globals.cc
+// Description: Global variables
+
 #include "shared/pch.hh"
 
 #include "shared/globals.hh"
diff --git a/src/game/shared/globals.hh b/src/game/shared/globals.hh
index 39a12a7..4c02f43 100644
--- a/src/game/shared/globals.hh
+++ b/src/game/shared/globals.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: globals.hh
+// Description: Global variables
+
+#ifndef SHARED_GLOBALS_HH
+#define SHARED_GLOBALS_HH
 #pragma once
 
 namespace globals
@@ -17,3 +24,5 @@ namespace globals
 {
 extern std::uint64_t curtime;
 } // namespace globals
+
+#endif
diff --git a/src/game/shared/pch.hh b/src/game/shared/pch.hh
index e978e0f..13afb80 100644
--- a/src/game/shared/pch.hh
+++ b/src/game/shared/pch.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: pch.hh
+// Description: Precompiled header
+
+#ifndef SHARED_PCH_HH
+#define SHARED_PCH_HH
 #pragma once
 
 #include <core/pch.hh> // inherit dependent includes from core.lib
@@ -17,3 +24,5 @@
 
 #include <spdlog/sinks/basic_file_sink.h>
 #include <spdlog/sinks/stdout_color_sinks.h>
+
+#endif
diff --git a/src/game/shared/protocol.cc b/src/game/shared/protocol.cc
index d274955..9b18f8a 100644
--- a/src/game/shared/protocol.cc
+++ b/src/game/shared/protocol.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: protocol.cc
+// Description: Network protocol on top of ENet
+
 #include "shared/pch.hh"
 
 #include "shared/protocol.hh"
diff --git a/src/game/shared/protocol.hh b/src/game/shared/protocol.hh
index 2582406..46e0202 100644
--- a/src/game/shared/protocol.hh
+++ b/src/game/shared/protocol.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: protocol.hh
+// Description: Network protocol on top of ENet
+
+#ifndef SHARED_PROTOCOL_HH
+#define SHARED_PROTOCOL_HH
 #pragma once
 
 #include "shared/world/chunk.hh"
@@ -210,3 +217,5 @@ struct protocol::DimensionInfo final : public protocol::Base<0x0012> {
     std::string name;
     float gravity;
 };
+
+#endif
diff --git a/src/game/shared/splash.cc b/src/game/shared/splash.cc
index 86ed0d0..86b71bc 100644
--- a/src/game/shared/splash.cc
+++ b/src/game/shared/splash.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: splash.cc
+// Description: Randomized text messages
+
 #include "shared/pch.hh"
 
 #include "shared/splash.hh"
@@ -39,7 +44,7 @@ static void splash_init_filename(std::string_view filename)
         splash_random.seed(std::random_device()());
     }
     else {
-        splash_lines.push_back(std::format("{}: {}", filename, physfs_error()));
+        splash_lines.push_back(std::format("{}: {}", filename, physfs::last_error()));
         splash_random.seed(std::random_device()());
     }
 }
diff --git a/src/game/shared/splash.hh b/src/game/shared/splash.hh
index be80cd6..0acfe3b 100644
--- a/src/game/shared/splash.hh
+++ b/src/game/shared/splash.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: splash.hh
+// Description: Randomized text messages
+
+#ifndef SHARED_SPLASH_HH
+#define SHARED_SPLASH_HH
 #pragma once
 
 namespace splash
@@ -6,3 +13,5 @@ void init_client(void);
 void init_server(void);
 std::string_view get(void);
 } // namespace splash
+
+#endif
diff --git a/src/game/shared/types.hh b/src/game/shared/types.hh
index 792ed0f..801206c 100644
--- a/src/game/shared/types.hh
+++ b/src/game/shared/types.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: types.hh
+// Description: Type definitions
+
+#ifndef SHARED_TYPES_HH
+#define SHARED_TYPES_HH
 #pragma once
 
 using item_id = std::uint32_t;
@@ -38,3 +45,5 @@ struct std::hash<chunk_pos_xz> final {
         return value;
     }
 };
+
+#endif
diff --git a/src/game/shared/world/chunk.cc b/src/game/shared/world/chunk.cc
index 10da80e..2840fc1 100644
--- a/src/game/shared/world/chunk.cc
+++ b/src/game/shared/world/chunk.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chunk.cc
+// Description: A single chunk of voxels
+
 #include "shared/pch.hh"
 
 #include "shared/world/chunk.hh"
diff --git a/src/game/shared/world/chunk.hh b/src/game/shared/world/chunk.hh
index f8e38b4..b0b0604 100644
--- a/src/game/shared/world/chunk.hh
+++ b/src/game/shared/world/chunk.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chunk.hh
+// Description: A single chunk of voxels
+
+#ifndef SHARED_WORLD_CHUNK_HH
+#define SHARED_WORLD_CHUNK_HH
 #pragma once
 
 #include "shared/world/voxel_storage.hh"
@@ -35,3 +42,5 @@ private:
     VoxelStorage m_voxels;
     unsigned int m_biome;
 };
+
+#endif
diff --git a/src/game/shared/world/chunk_aabb.hh b/src/game/shared/world/chunk_aabb.hh
index 0f8851c..7cf042c 100644
--- a/src/game/shared/world/chunk_aabb.hh
+++ b/src/game/shared/world/chunk_aabb.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: chunk_aabb.hh
+// Description: Axis-aligned bounding box for chunk-domain coordinates
+
+#ifndef SHARED_WORLD_CHUNK_AABB_HH
+#define SHARED_WORLD_CHUNK_AABB_HH
 #pragma once
 
 #include "core/math/aabb.hh"
@@ -5,3 +12,5 @@
 #include "shared/types.hh"
 
 using ChunkAABB = math::AABB<chunk_pos::value_type>;
+
+#endif
diff --git a/src/game/shared/world/dimension.cc b/src/game/shared/world/dimension.cc
index 84ca539..393aa0c 100644
--- a/src/game/shared/world/dimension.cc
+++ b/src/game/shared/world/dimension.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: dimension.cc
+// Description: A single world
+
 #include "shared/pch.hh"
 
 #include "shared/world/dimension.hh"
diff --git a/src/game/shared/world/dimension.hh b/src/game/shared/world/dimension.hh
index b57640a..9845c5a 100644
--- a/src/game/shared/world/dimension.hh
+++ b/src/game/shared/world/dimension.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: dimension.hh
+// Description: A single world
+
+#ifndef SHARED_WORLD_DIMENSION_HH
+#define SHARED_WORLD_DIMENSION_HH
 #pragma once
 
 #include "shared/const.hh"
@@ -81,3 +88,5 @@ struct VoxelSetEvent final {
     local_pos lpos;
     Chunk* chunk;
 };
+
+#endif
diff --git a/src/game/shared/world/feature.cc b/src/game/shared/world/feature.cc
index 3974082..1226b1f 100644
--- a/src/game/shared/world/feature.cc
+++ b/src/game/shared/world/feature.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: feature.cc
+// Description: A world generation feature
+
 #include "shared/pch.hh"
 
 #include "shared/world/feature.hh"
diff --git a/src/game/shared/world/feature.hh b/src/game/shared/world/feature.hh
index b80869d..820ddc7 100644
--- a/src/game/shared/world/feature.hh
+++ b/src/game/shared/world/feature.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: feature.hh
+// Description: A world generation feature
+
+#ifndef SHARED_WORLD_FEATURE_HH
+#define SHARED_WORLD_FEATURE_HH
 #pragma once
 
 #include "shared/types.hh"
@@ -17,3 +24,5 @@ public:
     void place(const voxel_pos& vpos, const chunk_pos& cpos, Chunk& chunk) const;
     void place(const voxel_pos& vpos, const chunk_pos& cpos, VoxelStorage& voxels) const;
 };
+
+#endif
diff --git a/src/game/shared/world/item.cc b/src/game/shared/world/item.cc
index bc1546a..207e9da 100644
--- a/src/game/shared/world/item.cc
+++ b/src/game/shared/world/item.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: item.cc
+// Description: Item metadata
+
 #include "shared/pch.hh"
 
 #include "shared/world/item.hh"
diff --git a/src/game/shared/world/item.hh b/src/game/shared/world/item.hh
index bcec37a..3786b19 100644
--- a/src/game/shared/world/item.hh
+++ b/src/game/shared/world/item.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: item.hh
+// Description: Item metadata
+
+#ifndef SHARED_WORLD_ITEM_HH
+#define SHARED_WORLD_ITEM_HH
 #pragma once
 
 #include "core/resource/resource.hh"
@@ -73,3 +80,5 @@ constexpr resource_ptr<TextureGUI>& Item::get_cached_texture(void) const noexcep
 {
     return m_cached_texture;
 }
+
+#endif
diff --git a/src/game/shared/world/item_registry.cc b/src/game/shared/world/item_registry.cc
index c7d8d9b..6f5a8a0 100644
--- a/src/game/shared/world/item_registry.cc
+++ b/src/game/shared/world/item_registry.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: item_registry.cc
+// Description: Registry for all the items in the game
+
 #include "shared/pch.hh"
 
 #include "shared/world/item_registry.hh"
diff --git a/src/game/shared/world/item_registry.hh b/src/game/shared/world/item_registry.hh
index f8fe641..588211d 100644
--- a/src/game/shared/world/item_registry.hh
+++ b/src/game/shared/world/item_registry.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: item_registry.hh
+// Description: Registry for all the items in the game
+
+#ifndef SHARED_WORLD_ITEM_REGISTRY_HH
+#define SHARED_WORLD_ITEM_REGISTRY_HH
 #pragma once
 
 #include "shared/world/item.hh"
@@ -24,3 +31,5 @@ namespace item_registry
 {
 std::uint64_t get_checksum(void);
 } // namespace item_registry
+
+#endif
diff --git a/src/game/shared/world/ray_aabb.cc b/src/game/shared/world/ray_aabb.cc
index f6f2638..9bc2ee0 100644
--- a/src/game/shared/world/ray_aabb.cc
+++ b/src/game/shared/world/ray_aabb.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: ray_aabb.cc
+// Description: Check ray intersections against an AABB
+
 #include "shared/pch.hh"
 
 #include "shared/world/ray_aabb.hh"
diff --git a/src/game/shared/world/ray_aabb.hh b/src/game/shared/world/ray_aabb.hh
index 49c0846..640a02c 100644
--- a/src/game/shared/world/ray_aabb.hh
+++ b/src/game/shared/world/ray_aabb.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: ray_aabb.hh
+// Description: Check ray intersections against an AABB
+
+#ifndef SHARED_WORLD_RAY_AABB_HH
+#define SHARED_WORLD_RAY_AABB_HH
 #pragma once
 
 #include "core/math/aabb.hh"
@@ -28,3 +35,5 @@ constexpr const glm::fvec3& RayAABB::direction(void) const noexcept
 {
     return m_direction;
 }
+
+#endif
diff --git a/src/game/shared/world/ray_dda.cc b/src/game/shared/world/ray_dda.cc
index 5dbf82e..45480b8 100644
--- a/src/game/shared/world/ray_dda.cc
+++ b/src/game/shared/world/ray_dda.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: ray_dda.cc
+// Description: Fast voxel grid traversal with an arbitrary starting position
+
 #include "shared/pch.hh"
 
 #include "shared/world/ray_dda.hh"
diff --git a/src/game/shared/world/ray_dda.hh b/src/game/shared/world/ray_dda.hh
index 72f746e..c3cbb09 100644
--- a/src/game/shared/world/ray_dda.hh
+++ b/src/game/shared/world/ray_dda.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: ray_dda.hh
+// Description: Fast voxel grid traversal with an arbitrary starting position
+
+#ifndef SHARED_WORLD_RAY_DDA_HH
+#define SHARED_WORLD_RAY_DDA_HH
 #pragma once
 
 #include "shared/types.hh"
@@ -30,3 +37,5 @@ public:
     voxel_pos vnormal;
     voxel_pos vpos;
 };
+
+#endif
diff --git a/src/game/shared/world/voxel.cc b/src/game/shared/world/voxel.cc
index 4f47c2d..71ef7b8 100644
--- a/src/game/shared/world/voxel.cc
+++ b/src/game/shared/world/voxel.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: voxel.cc
+// Description: Voxel metadata... A metavoxel!
+
 #include "shared/pch.hh"
 
 #include "shared/world/voxel.hh"
diff --git a/src/game/shared/world/voxel.hh b/src/game/shared/world/voxel.hh
index 0a8c4a3..8f6e344 100644
--- a/src/game/shared/world/voxel.hh
+++ b/src/game/shared/world/voxel.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: voxel.hh
+// Description: Voxel metadata... A metavoxel!
+
+#ifndef SHARED_WORLD_VOXEL_HH
+#define SHARED_WORLD_VOXEL_HH
 #pragma once
 
 #include "core/math/aabb.hh"
@@ -269,3 +276,5 @@ constexpr bool Voxel::is_surface_material(void) const noexcept
 {
     return m_surface_material == Material;
 }
+
+#endif
diff --git a/src/game/shared/world/voxel_registry.cc b/src/game/shared/world/voxel_registry.cc
index f950a4d..530b100 100644
--- a/src/game/shared/world/voxel_registry.cc
+++ b/src/game/shared/world/voxel_registry.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: voxel_registry.cc
+// Description: Registry for all the voxels in the game
+
 #include "shared/pch.hh"
 
 #include "shared/world/voxel_registry.hh"
diff --git a/src/game/shared/world/voxel_registry.hh b/src/game/shared/world/voxel_registry.hh
index 5dbaf50..4e60808 100644
--- a/src/game/shared/world/voxel_registry.hh
+++ b/src/game/shared/world/voxel_registry.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: voxel_registry.hh
+// Description: Registry for all the voxels in the game
+
+#ifndef SHARED_WORLD_VOXEL_REGISTRY_HH
+#define SHARED_WORLD_VOXEL_REGISTRY_HH
 #pragma once
 
 #include "shared/world/voxel.hh"
@@ -24,3 +31,5 @@ namespace voxel_registry
 {
 std::uint64_t get_checksum(void);
 } // namespace voxel_registry
+
+#endif
diff --git a/src/game/shared/world/voxel_storage.cc b/src/game/shared/world/voxel_storage.cc
index 43ca116..7890894 100644
--- a/src/game/shared/world/voxel_storage.cc
+++ b/src/game/shared/world/voxel_storage.cc
@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: voxel_storage.cc
+// Description: Storage for voxels in a chunk
+
 #include "shared/pch.hh"
 
 #include "shared/world/voxel_storage.hh"
diff --git a/src/game/shared/world/voxel_storage.hh b/src/game/shared/world/voxel_storage.hh
index ef427b3..e3d149a 100644
--- a/src/game/shared/world/voxel_storage.hh
+++ b/src/game/shared/world/voxel_storage.hh
@@ -1,3 +1,10 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright (c) 2025 Kirill Dmitrievich
+// File: voxel_storage.hh
+// Description: Storage for voxels in a chunk
+
+#ifndef SHARED_WORLD_VOXEL_STORAGE_HH
+#define SHARED_WORLD_VOXEL_STORAGE_HH
 #pragma once
 
 #include "shared/const.hh"
@@ -12,3 +19,5 @@ public:
     void serialize(WriteBuffer& buffer) const;
     void deserialize(ReadBuffer& buffer);
 };
+
+#endif