diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index dd03e8d0..b8b42731 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -18,25 +18,43 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        os: [windows-latest, ubuntu-latest, macos-latest]
+        # os: [windows-latest, ubuntu-latest, macos-latest] // TODO:
+        os: [windows-latest, ubuntu-24.04]
         build-variant: [Debug, Release]
     steps:
       - uses: actions/checkout@v4
 
       # TODO: Install GCC without using a script.
-      - if: matrix.os == 'ubuntu-latest'
+      - if: matrix.os == 'ubuntu-24.04'
         name: Installing GCC
         uses: egor-tensin/setup-gcc@v1
         with:
-          version: 12
+          version: 14
 
-      - if: matrix.os == 'ubuntu-latest'
+      # - if: matrix.os == 'ubuntu-24.04'
+      #   name: Installing GCC
+      #   run: |
+      #       sudo apt-get install gcc-14.2.0 g++-14.2.0
+      #       echo "gcc=$gcc" >> $env:GITHUB_OUTPUT
+      #       echo "gxx=$gxx" >> $env:GITHUB_OUTPUT
+      - if: matrix.os == 'ubuntu-24.04'
+        name: Setup Ninja
+        uses: ashutoshvarma/setup-ninja@master
+        with:
+          version: 1.12.1
+
+      - if: matrix.os == 'ubuntu-24.04'
         name: Installing Linux dependencies
         run: |
             sudo apt update
             sudo apt-get install -y libx11-dev libxkbcommon-x11-dev libx11-xcb-dev
 
-      - name: Configuring
+      - if: matrix.os == 'ubuntu-24.04'
+        name: Configuring
+        run: cmake -B build -G Ninja -DCMAKE_BUILD_TYPE=${{matrix.build-variant}} -DCORE_BUILD_UNITY=OFF # TODO: Re-enable unity build.
+
+      - if: matrix.os != 'ubuntu-24.04'
+        name: Configuring
         run: cmake -B build -DCMAKE_BUILD_TYPE=${{matrix.build-variant}} -DCORE_BUILD_UNITY=OFF # TODO: Re-enable unity build.
 
       - name: Building
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d89b002a..933f4cc7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.20)
+cmake_minimum_required(VERSION 3.28.2)
 
 project(core VERSION 0.0.1)
 
@@ -18,6 +18,7 @@ set(CMAKE_PDB_OUTPUT_DIRECTORY     "${CMAKE_BINARY_DIR}/bin/$<CONFIG>")
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin/$<CONFIG>")
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin/$<CONFIG>")
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/bin/$<CONFIG>")
+set(PREBUILT_MODULE_PATH           "${CMAKE_BINARY_DIR}/bin/$<CONFIG>")
 
 # Global compile definitions.
 set(GLOBAL_COMPILE_DEFINITIONS
@@ -34,9 +35,11 @@ set(GLOBAL_COMPILE_DEFINITIONS
     $<$<PLATFORM_ID:Darwin>:PLATFORM_MACOS=1>
 )
 
+set(CMAKE_CXX_STANDARD 20)
+
 # Global compile options.
 if(MSVC)
-    set(GLOBAL_COMPILE_OPTIONS -W4 -WX -std:c++20 -Zc:preprocessor -wd5105)
+    set(GLOBAL_COMPILE_OPTIONS -W4 -WX -std:c++20 -Zc:preprocessor -wd5105 -wd4273)
 else()
     # TODO: -Wno-deprecated-declarations is due to doctest.h sprintf() function.
     set(GLOBAL_COMPILE_OPTIONS -Wall -Wextra -pedantic -Werror -std=c++2b -fno-exceptions -Wno-invalid-offsetof -Wno-nested-anon-types -Wno-c++11-narrowing -Wno-gnu-zero-variadic-macro-arguments -Wno-deprecated-declarations -Wno-enum-constexpr-conversion -Wno-unknown-warning-option
diff --git a/core/CMakeLists.txt b/core/CMakeLists.txt
index 298f1276..fae5a380 100644
--- a/core/CMakeLists.txt
+++ b/core/CMakeLists.txt
@@ -1,8 +1,6 @@
 set(HEADER_FILES
-    base64.h
     defer.h
     defines.h
-    ecs.h
     formatter.h
     hash.h
     json.h
@@ -26,8 +24,6 @@ set(HEADER_FILES
 )
 
 set(SOURCE_FILES
-    base64.cpp
-    ecs.cpp
     formatter.cpp
     json.cpp
     log.cpp
@@ -76,6 +72,18 @@ if(${CORE_BUILD_STATIC})
     set(BUILD_TYPE STATIC)
 endif()
 add_library(core ${BUILD_TYPE} ${HEADER_FILES} ${SOURCE_FILES})
+
+# TODO:
+target_sources(core
+  PUBLIC
+    FILE_SET all_my_modules TYPE CXX_MODULES
+    BASE_DIRS
+        ${PROJECT_SOURCE_DIR}
+    FILES
+        base64.cppm
+        ecs.cppm
+)
+
 target_link_libraries(core PUBLIC ${LIBS})
 target_compile_options(core PRIVATE ${GLOBAL_COMPILE_OPTIONS})
 target_compile_definitions(core PRIVATE ${GLOBAL_COMPILE_DEFINITIONS})
diff --git a/core/base64.cpp b/core/base64.cppm
similarity index 52%
rename from core/base64.cpp
rename to core/base64.cppm
index 1dd6ef63..ad159ded 100644
--- a/core/base64.cpp
+++ b/core/base64.cppm
@@ -1,9 +1,23 @@
-#include "core/base64.h"
+module;
+
+#include "core/export.h"
+#include "core/defines.h"
+#include "core/export.h"
+#include "core/memory/memory.h"
+#include "core/containers/string.h"
+
+export module base64;
+
+/*
+	TODO:
+	- [ ] Should decode return a String or an Array<u8>?
+	- [ ] Should use Result<T>?
+*/
 
 inline static constexpr const char *BASE64_CHARACTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
-String
-base64_encode(const u8 *data, u64 size, memory::Allocator *allocator)
+export CORE_API String
+base64_encode(const u8 *data, u64 size, memory::Allocator *allocator = memory::heap_allocator())
 {
 	String out = string_init(allocator);
 
@@ -30,8 +44,8 @@ base64_encode(const u8 *data, u64 size, memory::Allocator *allocator)
 	return out;
 }
 
-String
-base64_decode(const String &data, memory::Allocator *allocator)
+export CORE_API String
+base64_decode(const String &data, memory::Allocator *allocator = memory::heap_allocator())
 {
 	constexpr auto index = [](const String &data, char c) -> u8 {
 		for (u8 i = 0; i < data.count; ++i)
@@ -81,4 +95,34 @@ base64_decode(const String &data, memory::Allocator *allocator)
 	}
 
 	return out;
+}
+
+export inline String
+base64_encode(const Block &data, memory::Allocator *allocator = memory::heap_allocator())
+{
+	return base64_encode((const u8 *)data.data, data.size, allocator);
+}
+
+export inline String
+base64_encode(const Array<u8> &data, memory::Allocator *allocator = memory::heap_allocator())
+{
+	return base64_encode(data.data, data.count, allocator);
+}
+
+export inline String
+base64_encode(const String &data, memory::Allocator *allocator = memory::heap_allocator())
+{
+	return base64_encode((const u8 *)data.data, data.count, allocator);
+}
+
+export inline String
+base64_encode(const char *data, memory::Allocator *allocator = memory::heap_allocator())
+{
+	return base64_encode(string_literal(data), allocator);
+}
+
+export inline String
+base64_decode(const char *data, memory::Allocator *allocator = memory::heap_allocator())
+{
+	return base64_decode(string_literal(data), allocator);
 }
\ No newline at end of file
diff --git a/core/base64.h b/core/base64.h
deleted file mode 100644
index 0d24c9d6..00000000
--- a/core/base64.h
+++ /dev/null
@@ -1,48 +0,0 @@
-#pragma once
-
-#include "core/defines.h"
-#include "core/export.h"
-#include "core/memory/memory.h"
-#include "core/containers/string.h"
-
-/*
-	TODO:
-	- [ ] Should decode return a String or an Array<u8>?
-	- [ ] Should use Result<T>?
-*/
-
-CORE_API String
-base64_encode(const u8 *data, u64 size, memory::Allocator *allocator = memory::heap_allocator());
-
-inline static String
-base64_encode(const Block &data, memory::Allocator *allocator = memory::heap_allocator())
-{
-	return base64_encode((const u8 *)data.data, data.size, allocator);
-}
-
-inline static String
-base64_encode(const Array<u8> &data, memory::Allocator *allocator = memory::heap_allocator())
-{
-	return base64_encode(data.data, data.count, allocator);
-}
-
-inline static String
-base64_encode(const String &data, memory::Allocator *allocator = memory::heap_allocator())
-{
-	return base64_encode((const u8 *)data.data, data.count, allocator);
-}
-
-inline static String
-base64_encode(const char *data, memory::Allocator *allocator = memory::heap_allocator())
-{
-	return base64_encode(string_literal(data), allocator);
-}
-
-CORE_API String
-base64_decode(const String &data, memory::Allocator *allocator = memory::heap_allocator());
-
-inline static String
-base64_decode(const char *data, memory::Allocator *allocator = memory::heap_allocator())
-{
-	return base64_decode(string_literal(data), allocator);
-}
\ No newline at end of file
diff --git a/core/ecs.cpp b/core/ecs.cpp
deleted file mode 100644
index 8009a9a3..00000000
--- a/core/ecs.cpp
+++ /dev/null
@@ -1,13 +0,0 @@
-#include "ecs.h"
-
-#include <atomic>
-
-namespace ecs
-{
-	Entity
-	entity_new()
-	{
-		static std::atomic<u64> id = 0;
-		return Entity{id.fetch_add(1)};
-	}
-}
\ No newline at end of file
diff --git a/core/ecs.h b/core/ecs.cppm
similarity index 86%
rename from core/ecs.h
rename to core/ecs.cppm
index 6aa0c5dc..ab7c297d 100644
--- a/core/ecs.h
+++ b/core/ecs.cppm
@@ -1,4 +1,4 @@
-#pragma once
+module;
 
 #include "core/export.h"
 #include "core/defines.h"
@@ -8,10 +8,13 @@
 #include <type_traits>
 #include <typeinfo>
 #include <concepts>
+#include <atomic>
+
+export module ecs;
 
 namespace ecs
 {
-	struct Entity
+	export struct Entity
 	{
 		u64 id = U64_MAX;
 
@@ -28,9 +31,6 @@ namespace ecs
 		}
 	};
 
-	CORE_API Entity
-	entity_new();
-
 	typedef u64 Component_Hash;
 
 	struct IComponent_Table
@@ -121,7 +121,7 @@ namespace ecs
 		}
 	};
 
-	struct ECS
+	export struct ECS
 	{
 		Hash_Table<Component_Hash, IComponent_Table *> component_tables;
 
@@ -186,13 +186,13 @@ namespace ecs
 		}
 	};
 
-	inline static ECS
+	export inline ECS
 	ecs_new()
 	{
 		return {hash_table_init<Component_Hash, IComponent_Table *>()};
 	}
 
-	inline static void
+	export inline void
 	ecs_free(ECS &self)
 	{
 		for (auto &[_, v] : self.component_tables)
@@ -201,50 +201,59 @@ namespace ecs
 		hash_table_deinit(self.component_tables);
 	}
 
-	template <typename T>
-	inline static void
+	export template <typename T>
+	inline void
 	ecs_add_table(ECS &self)
 	{
-		hash_table_insert(self.component_tables, (u64)typeid(T).hash_code(), (IComponent_Table *)memory::allocate_and_call_constructor<Component_Table<T>>());
+		const std::type_info &info = typeid(T);
+		hash_table_insert(self.component_tables, (u64)info.hash_code(), (IComponent_Table *)memory::allocate_and_call_constructor<Component_Table<T>>());
 	}
 
-	template <Component_Type T>
-	inline static const T *
+	export template <Component_Type T>
+	inline const T *
 	ecs_component_read(ECS &self, Entity e)
 	{
 		return self.read<T>(e);
 	}
 
-	template <Component_Type T>
-	inline static T *
+	export template <Component_Type T>
+	inline T *
 	ecs_component_write(ECS &self, Entity e)
 	{
 		return self.write<T>(e);
 	}
 
-	template <Component_Type T>
-	inline static void
+	export template <Component_Type T>
+	inline void
 	ecs_component_remove(ECS &self, Entity e)
 	{
 		self.remove<T>(e);
 	}
 
-	template <Component_Type ...TArgs>
-	inline static Array<Entity>
+	export template <Component_Type ...TArgs>
+	inline Array<Entity>
 	ecs_entity_list(ECS &self)
 	{
 		return self.list<TArgs...>();
 	}
 
 	// TODO: Test this.
-	inline static void
+	export inline void
 	ecs_reload(ECS &self)
 	{
 		self.reload();
 	}
 
+	export CORE_API Entity
+	entity_new()
+	{
+		static std::atomic<u64> id = 0;
+		return Entity{id.fetch_add(1)};
+	}
+
 	// TODO: Rename this to ecs_entity_remove()?
-	inline static void
+	// TODO: Should set the id of the removed entity to U64_MAX?
+	export inline void
 	ecs_entity_free(ECS &self, Entity e)
 	{
 		self.entity_free(e);
diff --git a/core/hash.h b/core/hash.h
index 2c19a67e..8a1ef754 100644
--- a/core/hash.h
+++ b/core/hash.h
@@ -3,7 +3,7 @@
 #include "core/defines.h"
 
 // 32 bit Fowler-Noll-Vo hash.
-inline static u64
+inline u64
 hash_fnv_x32(const void *key, u64 key_length)
 {
 	const u32 p = 16777619U;
@@ -22,7 +22,7 @@ hash_fnv_x32(const void *key, u64 key_length)
 }
 
 template <typename T>
-inline static u64
+inline u64
 hash(const T &)
 {
 	static_assert(sizeof(T) == 0, "There is no 'u64 hash(const T &)' function overload defined for this type.");
@@ -30,86 +30,86 @@ hash(const T &)
 }
 
 template <typename T>
-inline static u64
+inline u64
 hash(T *key)
 {
 	return u64(key);
 };
 
 template <typename T>
-inline static u64
+inline u64
 hash(const T *key)
 {
 	return u64(key);
 };
 
-inline static u64
+inline u64
 hash(bool key)
 {
 	return u64(key);
 }
 
-inline static u64
+inline u64
 hash(char key)
 {
 	return u64(key);
 }
 
-inline static u64
+inline u64
 hash(i8 key)
 {
 	return u64(key);
 }
 
-inline static u64
+inline u64
 hash(i16 key)
 {
 	return u64(key);
 }
 
-inline static u64
+inline u64
 hash(i32 key)
 {
 	return u64(key);
 }
 
-inline static u64
+inline u64
 hash(i64 key)
 {
 	return u64(key);
 }
 
-inline static u64
+inline u64
 hash(u8 key)
 {
 	return u64(key);
 }
 
-inline static u64
+inline u64
 hash(u16 key)
 {
 	return u64(key);
 }
 
-inline static u64
+inline u64
 hash(u32 key)
 {
 	return u64(key);
 }
 
-inline static u64
+inline u64
 hash(u64 key)
 {
 	return u64(key);
 }
 
-inline static u64
+inline u64
 hash(f32 key)
 {
 	return hash_fnv_x32(&key, sizeof(f32));
 }
 
-inline static u64
+inline u64
 hash(f64 key)
 {
 	return hash_fnv_x32(&key, sizeof(f64));
diff --git a/core/json.cpp b/core/json.cpp
index 8ea42bd9..7e9da69b 100644
--- a/core/json.cpp
+++ b/core/json.cpp
@@ -2,6 +2,7 @@
 
 #include "core/platform/platform.h"
 
+#include <stdlib.h>
 #include <cerrno>
 
 struct JSON_Parser
diff --git a/core/memory/heap_allocator.cpp b/core/memory/heap_allocator.cpp
index d011e22c..7aff51c9 100644
--- a/core/memory/heap_allocator.cpp
+++ b/core/memory/heap_allocator.cpp
@@ -3,6 +3,7 @@
 #include "core/log.h"
 #include "core/platform/platform.h"
 
+#include <stdio.h>
 #include <stdlib.h>
 #include <inttypes.h>
 #if DEBUG
diff --git a/core/memory/memory.h b/core/memory/memory.h
index 16d99294..4e26ce99 100644
--- a/core/memory/memory.h
+++ b/core/memory/memory.h
@@ -37,35 +37,35 @@ namespace memory
 	CORE_API Allocator *
 	temp_allocator();
 
-	inline static void *
+	inline void *
 	allocate(u64 size)
 	{
 		auto allocator = heap_allocator();
 		return allocator->allocate(size);
 	}
 
-	inline static void *
+	inline void *
 	allocate(Allocator *allocator, u64 size)
 	{
 		return allocator->allocate(size);
 	}
 
 	template <typename T>
-	inline static T *
+	inline T *
 	allocate()
 	{
 		return (T *)allocate(sizeof(T));
 	}
 
 	template <typename T>
-	inline static T *
+	inline T *
 	allocate(Allocator *allocator)
 	{
 		return (T *)allocate(allocator, sizeof(T));
 	}
 
 	template <typename T, typename ...TArgs>
-	inline static T *
+	inline T *
 	allocate_and_call_constructor(TArgs &&...args)
 	{
 		T *data = allocate<T>();
@@ -74,7 +74,7 @@ namespace memory
 	}
 
 	template <typename T, typename ...TArgs>
-	inline static T *
+	inline T *
 	allocate_and_call_constructor(Allocator *allocator, TArgs &&...args)
 	{
 		T *data = allocate<T>(allocator);
@@ -82,7 +82,7 @@ namespace memory
 		return data;
 	}
 
-	inline static void *
+	inline void *
 	allocate_zeroed(u64 size)
 	{
 		void *data = allocate(size);
@@ -90,7 +90,7 @@ namespace memory
 		return data;
 	}
 
-	inline static void *
+	inline void *
 	allocate_zeroed(Allocator *allocator, u64 size)
 	{
 		void *data = allocate(allocator, size);
@@ -99,34 +99,34 @@ namespace memory
 	}
 
 	template <typename T>
-	inline static T *
+	inline T *
 	allocate_zeroed()
 	{
 		return (T *)allocate_zeroed(sizeof(T));
 	}
 
 	template <typename T>
-	inline static T *
+	inline T *
 	allocate_zeroed(Allocator *allocator)
 	{
 		return (T *)allocate_zeroed(allocator, sizeof(T));
 	}
 
-	inline static void
+	inline void
 	deallocate(void *data)
 	{
 		auto allocator = heap_allocator();
 		allocator->deallocate(data);
 	}
 
-	inline static void
+	inline void
 	deallocate(Allocator *allocator, void *data)
 	{
 		allocator->deallocate(data);
 	}
 
 	template <typename T>
-	inline static void
+	inline void
 	deallocate_and_call_destructor(T *data)
 	{
 		data->~T();
@@ -134,7 +134,7 @@ namespace memory
 	}
 
 	template <typename T>
-	inline static void
+	inline void
 	deallocate_and_call_destructor(Allocator *allocator, T *data)
 	{
 		data->~T();
diff --git a/core/platform/platform_linux.cpp b/core/platform/platform_linux.cpp
index 248c89e9..86754593 100644
--- a/core/platform/platform_linux.cpp
+++ b/core/platform/platform_linux.cpp
@@ -20,6 +20,7 @@
 #include <pthread.h>
 #include <atomic>
 #include <inttypes.h>
+#include <stdio.h>
 
 static char current_executable_directory[PATH_MAX] = {};
 
diff --git a/core/serialization/json_serializer.h b/core/serialization/json_serializer.h
index 6e3b6a8d..1a018479 100644
--- a/core/serialization/json_serializer.h
+++ b/core/serialization/json_serializer.h
@@ -4,11 +4,12 @@
 #include "core/defines.h"
 #include "core/json.h"
 #include "core/log.h"
-#include "core/base64.h"
 #include "core/containers/array.h"
 #include "core/containers/string.h"
 #include "core/containers/hash_table.h"
 
+import base64;
+
 struct Json_Serializer
 {
 	memory::Allocator *allocator;
diff --git a/core/utils.h b/core/utils.h
index aa42597e..113ed3da 100644
--- a/core/utils.h
+++ b/core/utils.h
@@ -2,7 +2,7 @@
 
 #include "core/defines.h"
 
-inline static u64
+inline u64
 next_power_of_two(i32 value)
 {
 	--value;
diff --git a/unittest/CMakeLists.txt b/unittest/CMakeLists.txt
index abd393d9..5ac782bd 100644
--- a/unittest/CMakeLists.txt
+++ b/unittest/CMakeLists.txt
@@ -16,6 +16,7 @@ set(HEADER_FILES
 set(SOURCE_FILES
     src/unittest.cpp
     src/unittest_core.cpp
+    src/unittest_ecs.cpp
     src/unittest_containers.cpp
     src/unittest_platform.cpp
     src/unittest_reflect.cpp
diff --git a/unittest/src/unittest_core.cpp b/unittest/src/unittest_core.cpp
index a4aa205d..16e77981 100644
--- a/unittest/src/unittest_core.cpp
+++ b/unittest/src/unittest_core.cpp
@@ -1,5 +1,4 @@
 #include <core/json.h>
-#include <core/base64.h>
 #include <core/log.h>
 #include <core/result.h>
 #include <core/formatter.h>
@@ -8,6 +7,8 @@
 #include <core/memory/arena_allocator.h>
 #include <core/platform/platform.h>
 
+import base64;
+
 #include <doctest/doctest.h>
 
 TEST_CASE("[CORE]: Arena_Allocator")
diff --git a/unittest/src/unittest_ecs.cpp b/unittest/src/unittest_ecs.cpp
new file mode 100644
index 00000000..18437027
--- /dev/null
+++ b/unittest/src/unittest_ecs.cpp
@@ -0,0 +1,38 @@
+#include <core/defines.h>
+#include <core/defer.h>
+
+import ecs;
+
+#include <doctest/doctest.h>
+
+struct Position
+{
+	f32 x, y;
+};
+
+TEST_CASE("[ECS]")
+{
+	ecs::ECS world = ecs::ecs_new();
+	DEFER(ecs::ecs_free(world));
+
+	ecs::ecs_add_table<Position>(world);
+
+	ecs::Entity entity1 = ecs::entity_new();
+	DEFER(ecs::ecs_entity_free(world, entity1));
+	CHECK(entity1.id == 0);
+
+	auto *position_read = ecs::ecs_component_read<Position>(world, entity1);
+	CHECK(position_read == nullptr);
+
+	auto &position1 = *ecs::ecs_component_write<Position>(world, entity1);
+	position1 = Position{1.0f, 1.0f};
+
+	position_read = ecs::ecs_component_read<Position>(world, entity1);
+	CHECK(position_read != nullptr);
+	CHECK(position_read->x == 1.0f);
+	CHECK(position_read->y == 1.0f);
+
+	ecs::Entity entity2 = ecs::entity_new();
+	CHECK(entity2.id == 1);
+	DEFER(ecs::ecs_entity_free(world, entity2));
+}
\ No newline at end of file