Merge remote-tracking branch 'origin/master' into max/POC-ECS-homemade

44 files changed, 783 insertions, 173 deletions

diff --git a/.clang-format b/.clang-format
index 5d233eb..3ae6c28 100644
--- a/.clang-format
+++ b/.clang-format
@@ -22,6 +22,7 @@ AlignTrailingComments:
 ReflowComments: false
 AlignEscapedNewlines: DontAlign
 BreakBeforeBinaryOperators: All
+AlwaysBreakTemplateDeclarations: Yes
 ...
 
 # vim: ft=yaml
diff --git a/.clang-tidy b/.clang-tidy
index b242e3f..214a5ab 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -1,18 +1,35 @@
 Checks: '-*,readability-identifier-naming'
 CheckOptions:
-	- { key: readability-identifier-naming.EnumCase, value: lower_case }
-	- { key: readability-identifier-naming.GlobalFunctionCase, value: lower_case }
-	- { key: readability-identifier-naming.ClassCase, value: CamelCase }
-	- { key: readability-identifier-naming.ClassMethodCase, value: lower_case }
-	- { key: readability-identifier-naming.ClassMethodPrefix, value: '' }
-	- { key: readability-identifier-naming.ClassMemberCase, value: lower_case }
-	- { key: readability-identifier-naming.ClassMemberPrefix, value: '' }
-	- { key: readability-identifier-naming.GlobalConstantCase, value: UPPER_CASE }
-	- { key: readability-identifier-naming.GlobalConstantIgnoredRegexp, value: _.* }
-	- { key: readability-identifier-naming.GlobalVariableCase, value: lower_case }
-	- { key: readability-identifier-naming.GlobalVariableIgnoredRegexp, value: _.* }
-	- { key: readability-identifier-naming.MacroDefinitionCase, value: UPPER_CASE }
-	- { key: readability-identifier-naming.MacroDefinitionIgnoredRegexp, value: _.* }
-	- { key: readability-identifier-naming.StructCase, value: lower_case }
+  - key: 'readability-identifier-naming.EnumCase'
+    value: 'lower_case'
+  - key: 'readability-identifier-naming.GlobalFunctionCase'
+    value: 'lower_case'
+  - key: 'readability-identifier-naming.ClassCase'
+    value: 'CamelCase'
+  - key: 'readability-identifier-naming.MethodCase'
+    value: 'lower_case'
+  - key: 'readability-identifier-naming.MethodPrefix'
+    value: ''
+  - key: 'readability-identifier-naming.MemberCase'
+    value: 'lower_case'
+  - key: 'readability-identifier-naming.MemberPrefix'
+    value: ''
+  - key: 'readability-identifier-naming.ConstantCase'
+    value: 'UPPER_CASE'
+  - key: 'readability-identifier-naming.ConstantIgnoredRegexp'
+    value: '_.*'
+  - key: 'readability-identifier-naming.ConstantParameterCase'
+    value: 'lower_case'
+  - key: 'readability-identifier-naming.VariableCase'
+    value: 'lower_case'
+  - key: 'readability-identifier-naming.VariableIgnoredRegexp'
+    value: '_.*'
+  - key: 'readability-identifier-naming.MacroDefinitionCase'
+    value: 'UPPER_CASE'
+  - key: 'readability-identifier-naming.MacroDefinitionIgnoredRegexp'
+    value: '_.*'
+  - key: 'readability-identifier-naming.StructCase'
+    value: 'lower_case'
 
 # vim: ft=yaml
+
diff --git a/.editorconfig b/.editorconfig
index 1bd7da9..df2cf5e 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -5,7 +5,7 @@ indent_style = tab
 end_of_line = lf
 insert_final_newline = true
 
-[*.{md,yml}]
+[{*.{md,yml},.clang-*}]
 indent_style = space
 indent_size = 2
 
diff --git a/.gitmodules b/.gitmodules
index bb860c0..7dd39b2 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -3,7 +3,7 @@
 	url = https://github.com/google/googletest
 	shallow = true
 [submodule "lib/soloud/src"]
-	path = lib/soloud/src
+	path = lib/soloud
 	url = https://github.com/jarikomppa/soloud
 	shallow = true
 [submodule "lib/sdl2"]
diff --git a/.vscode/tasks.json b/.vscode/tasks.json
index 0fd5d23..19afa6f 100644
--- a/.vscode/tasks.json
+++ b/.vscode/tasks.json
@@ -1,28 +1,38 @@
 {
+    "version": "2.0.0",
     "tasks": [
         {
-            "type": "cppbuild",
-            "label": "C/C++: g++ build active file",
-            "command": "/usr/bin/g++",
+            "label": "configure",
+            "type": "shell",
+            "command": "cmake",
             "args": [
-                "-fdiagnostics-color=always",
-                "-g",
-                "${file}",
-                "-o",
-                "${fileDirname}/${fileBasenameNoExtension}"
+                "-G",
+                "Ninja",
+                "-B",
+                "${workspaceFolder}/mwe/ecs-homemade/build",  // Create build folder here
+                "${workspaceFolder}/mwe/ecs-homemade"  // Path to your source directory
             ],
-            "options": {
-                "cwd": "${fileDirname}"
+            "group": {
+                "kind": "build",
+                "isDefault": false
             },
-            "problemMatcher": [
-                "$gcc"
+            "problemMatcher": []
+        },
+        {
+            "label": "build",
+            "type": "shell",
+            "command": "cmake",
+            "args": [
+                "--build",
+                "${workspaceFolder}/mwe/ecs-homemade/build"  // Build directory
             ],
+            "dependsOn": "configure",  // Ensure the configure task runs first
             "group": {
                 "kind": "build",
                 "isDefault": true
             },
-            "detail": "Task generated by Debugger."
+            "problemMatcher": ["$gcc"],
+            "detail": "Generated task for building the project."
         }
-    ],
-    "version": "2.0.0"
+    ]
 }
diff --git a/contributing.md b/contributing.md
index 2ff411a..364e835 100644
--- a/contributing.md
+++ b/contributing.md
@@ -17,6 +17,12 @@
 # Code style
 
 - ASCII only
+- Class names are always singular
+- Explanatory comments are placed above the line(s) they are explaining
+- Source files should only contain comments that plainly state what the code is
+  supposed to do
+- Explanatory comments in headers may be used to clarify implementation design
+  decisions
 - Formatting nitty-gritty is handled by clang-format/clang-tidy (run `make
   format` in the root folder of this repository to format all sources files)
 - When using libraries of which the header include order is important, make
@@ -30,6 +36,29 @@
   as these are no longer accessible when the engine is installed
 - Getter and setter functions are appropriately prefixed with `get_` and
   `set_`.
+- Doxygen commands are used with a backslash instead of an at-sign (i.e.
+  `\brief` instead of `@brief`)
+- A singleton's instance is always accessed using a getter function that
+  instantiates its own class as a static variable within the getter function
+  scope, instead of storing the instance as a member variable directly:
+
+  ```cpp
+  class Bad {
+    static Bad instance;
+    Bad & get_instance() { return instance; }
+  };
+
+  class Good {
+    Good & get_instance() {
+      static Good instance;
+      return instance;
+    }
+  };
+  ```
+- Member variable default values should be directly defined in the class
+  declaration instead of using the constructor.
+- Header files declare either a single class or symbols within a single
+  namespace.
 
 ## CMakeLists specific
 
diff --git a/lib/soloud/src b/lib/soloud
-Subproject e82fd32c1f62183922f08c14c814a02b58db187
+Subproject e82fd32c1f62183922f08c14c814a02b58db187
diff --git a/lib/soloud/CMakeLists.txt b/lib/soloud/CMakeLists.txt
deleted file mode 100644
index aaccd96..0000000
--- a/lib/soloud/CMakeLists.txt
+++ /dev/null
@@ -1,97 +0,0 @@
-cmake_minimum_required(VERSION 3.28)
-
-set(CMAKE_C_STANDARD 11)
-set(CMAKE_CXX_STANDARD 20)
-
-add_compile_definitions(WITH_SDL2)
-
-add_subdirectory(../sdl2 sdl2)
-
-project(soloud C CXX)
-
-add_library(soloud SHARED
-	src/src/audiosource/ay/chipplayer.cpp
-	src/src/audiosource/ay/sndbuffer.cpp
-	src/src/audiosource/ay/sndchip.cpp
-	src/src/audiosource/ay/sndrender.cpp
-	src/src/audiosource/ay/soloud_ay.cpp
-	src/src/audiosource/monotone/soloud_monotone.cpp
-	src/src/audiosource/noise/soloud_noise.cpp
-	src/src/audiosource/openmpt/soloud_openmpt.cpp
-	src/src/audiosource/openmpt/soloud_openmpt_dll.c
-	src/src/audiosource/sfxr/soloud_sfxr.cpp
-	src/src/audiosource/speech/darray.cpp
-	src/src/audiosource/speech/klatt.cpp
-	src/src/audiosource/speech/resonator.cpp
-	src/src/audiosource/speech/soloud_speech.cpp
-	src/src/audiosource/speech/tts.cpp
-	src/src/audiosource/tedsid/sid.cpp
-	src/src/audiosource/tedsid/soloud_tedsid.cpp
-	src/src/audiosource/tedsid/ted.cpp
-	src/src/audiosource/vic/soloud_vic.cpp
-	src/src/audiosource/vizsn/soloud_vizsn.cpp
-	src/src/audiosource/wav/dr_impl.cpp
-	src/src/audiosource/wav/soloud_wav.cpp
-	src/src/audiosource/wav/soloud_wavstream.cpp
-	src/src/audiosource/wav/stb_vorbis.c
-
-	src/src/backend/alsa/soloud_alsa.cpp
-	src/src/backend/coreaudio/soloud_coreaudio.cpp
-	src/src/backend/jack/soloud_jack.cpp
-	src/src/backend/miniaudio/soloud_miniaudio.cpp
-	src/src/backend/nosound/soloud_nosound.cpp
-	src/src/backend/null/soloud_null.cpp
-	src/src/backend/openal/soloud_openal.cpp
-	src/src/backend/openal/soloud_openal_dll.c
-	src/src/backend/opensles/soloud_opensles.cpp
-	src/src/backend/oss/soloud_oss.cpp
-	src/src/backend/portaudio/soloud_portaudio.cpp
-	src/src/backend/portaudio/soloud_portaudio_dll.c
-	src/src/backend/sdl/soloud_sdl1.cpp
-	src/src/backend/sdl/soloud_sdl1_dll.c
-	src/src/backend/sdl/soloud_sdl2.cpp
-	src/src/backend/sdl/soloud_sdl2_dll.c
-	src/src/backend/sdl2_static/soloud_sdl2_static.cpp
-	src/src/backend/sdl_static/soloud_sdl_static.cpp
-	src/src/backend/wasapi/soloud_wasapi.cpp
-	src/src/backend/winmm/soloud_winmm.cpp
-	src/src/backend/xaudio2/soloud_xaudio2.cpp
-
-	src/src/core/soloud.cpp
-	src/src/core/soloud_audiosource.cpp
-	src/src/core/soloud_bus.cpp
-	src/src/core/soloud_core_3d.cpp
-	src/src/core/soloud_core_basicops.cpp
-	src/src/core/soloud_core_faderops.cpp
-	src/src/core/soloud_core_filterops.cpp
-	src/src/core/soloud_core_getters.cpp
-	src/src/core/soloud_core_setters.cpp
-	src/src/core/soloud_core_voicegroup.cpp
-	src/src/core/soloud_core_voiceops.cpp
-	src/src/core/soloud_fader.cpp
-	src/src/core/soloud_fft.cpp
-	src/src/core/soloud_fft_lut.cpp
-	src/src/core/soloud_file.cpp
-	src/src/core/soloud_filter.cpp
-	src/src/core/soloud_misc.cpp
-	src/src/core/soloud_queue.cpp
-	src/src/core/soloud_thread.cpp
-
-	# src/src/filter/soloud_bassboostfilter.cpp
-	# src/src/filter/soloud_biquadresonantfilter.cpp
-	# src/src/filter/soloud_dcremovalfilter.cpp
-	# src/src/filter/soloud_duckfilter.cpp
-	# src/src/filter/soloud_echofilter.cpp
-	# src/src/filter/soloud_eqfilter.cpp
-	# src/src/filter/soloud_fftfilter.cpp
-	# src/src/filter/soloud_flangerfilter.cpp
-	# src/src/filter/soloud_freeverbfilter.cpp
-	# src/src/filter/soloud_lofifilter.cpp
-	# src/src/filter/soloud_robotizefilter.cpp
-	# src/src/filter/soloud_waveshaperfilter.cpp
-)
-target_include_directories(soloud PRIVATE src/include)
-target_include_directories(soloud SYSTEM INTERFACE src/include)
-
-target_link_libraries(soloud PRIVATE SDL2)
-
diff --git a/mwe/ecs-homemade/inc/ComponentManager.hpp b/mwe/ecs-homemade/inc/ComponentManager.hpp
index 161ce71..d6da8e8 100644
--- a/mwe/ecs-homemade/inc/ComponentManager.hpp
+++ b/mwe/ecs-homemade/inc/ComponentManager.hpp
@@ -42,7 +42,8 @@ void ComponentManager::DeleteComponentsById(std::uint32_t id) {
 	}
 }
 
-template <typename T> void ComponentManager::DeleteComponents() {
+template <typename T>
+void ComponentManager::DeleteComponents() {
 	std::type_index type = typeid(
 		T); //Determine the type of T (this is used as the key of the unordered_map<>)
 
diff --git a/mwe/ecs-homemade/inc/GameObjectMax.h b/mwe/ecs-homemade/inc/GameObjectMax.h
index c88a834..3029053 100644
--- a/mwe/ecs-homemade/inc/GameObjectMax.h
+++ b/mwe/ecs-homemade/inc/GameObjectMax.h
@@ -7,7 +7,8 @@ class GameObject {
 public:
 	GameObject(std::uint32_t id, std::string name, std::string tag, int layer);
 
-	template <typename T, typename... Args> void AddComponent(Args &&... args);
+	template <typename T, typename... Args>
+	void AddComponent(Args &&... args);
 
 	std::uint32_t mId;
 	std::string mName;
diff --git a/readme.md b/readme.md
index 5351dfe..24bb66f 100644
--- a/readme.md
+++ b/readme.md
@@ -8,18 +8,45 @@ This repository contains:
 |`mwe/`|minimal working examples and proof-of-concepts|
 |`src/crepe/`|game engine source code|
 |`src/test/`|unit tests|
-|`src/example`|standalone examples using game engine|
+|`src/example/`|standalone examples using game engine|
 
 ## Compilation
 
 This repository uses CMake (the makefile in the root of this repository is for
-running auxiliary tasks only). Make sure you have initialized and updated the
-submodules before compiling.
+running auxiliary tasks only). See [src/readme.md](src/readme.md) for detailed
+building instructions.
+
+## Installing libraries
+
+The expected library (source) versions are included in this repository as git
+submodules. Follow these steps for manually building one of the required
+libraries from source:
+
+1. Ensure the git submodules are initialized:
+   ```
+   $ git submodule update --init --recursive --depth 1
+   ```
+2. `cd` into the library source folder:
+   ```
+   $ cd lib/googletest
+   or
+   $ cd lib/sdl2
+   or
+   $ cd lib/soloud/contrib
+   ```
+3. Configure the build, run the build and install:
+   ```
+   $ cmake -B build -G Ninja
+   $ ninja -C build
+   # ninja -C build install
+   ```
 
 ## Documentation
 
-API documentation is done using Doxygen. To generate the docs, run `make
-doxygen`.
+API documentation is done using Doxygen. To generate the docs, run
+```
+$ make doxygen
+```
 
 ## Code style
 
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 62ca9a0..09c60bd 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -3,16 +3,14 @@ cmake_minimum_required(VERSION 3.28)
 set(CMAKE_C_STANDARD 11)
 set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_EXPORT_COMPILE_COMMANDS 1)
-
-# enable debug features
 set(CMAKE_BUILD_TYPE Debug)
-add_compile_definitions(DEBUG)
-
-add_subdirectory(../lib/soloud soloud)
-add_subdirectory(../lib/googletest googletest)
 
 project(crepe C CXX)
 
+find_package(SDL2 REQUIRED)
+find_package(SoLoud REQUIRED)
+find_package(GTest REQUIRED)
+
 add_library(crepe SHARED)
 add_executable(test_main EXCLUDE_FROM_ALL)
 
@@ -20,9 +18,9 @@ target_include_directories(crepe
 	PUBLIC SYSTEM INTERFACE .
 )
 
-# TODO: libraries should be linked as PRIVATE
 target_link_libraries(crepe
-	PUBLIC soloud
+	PRIVATE soloud
+	PRIVATE SDL2
 )
 
 add_subdirectory(crepe)
diff --git a/src/crepe/CMakeLists.txt b/src/crepe/CMakeLists.txt
index 208ba1f..d85aef0 100644
--- a/src/crepe/CMakeLists.txt
+++ b/src/crepe/CMakeLists.txt
@@ -2,12 +2,30 @@ target_sources(crepe PUBLIC
 	Asset.cpp
 	Sound.cpp
 	SoundContext.cpp
+	ComponentManager.cpp
+	Component.cpp
+	GameObject.cpp
+	Collider.cpp
+	Rigidbody.cpp
+	Sprite.cpp
+	ScriptSystem.cpp
+	Script.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	Asset.h
 	Sound.h
 	SoundContext.h
+	ComponentManager.h
+	ComponentManager.hpp
+	Component.h
+	GameObject.h
+	GameObject.hpp
+	Collider.h
+	Rigidbody.h
+	Sprite.h
+	System.h
+	ScriptSystem.h
 )
 
 add_subdirectory(api)
diff --git a/src/crepe/Collider.cpp b/src/crepe/Collider.cpp
new file mode 100644
index 0000000..3f12afd
--- /dev/null
+++ b/src/crepe/Collider.cpp
@@ -0,0 +1,5 @@
+#include "Collider.h"
+
+using namespace crepe;
+
+Collider::Collider(int size) : size(size) {}
diff --git a/src/crepe/Collider.h b/src/crepe/Collider.h
new file mode 100644
index 0000000..120da05
--- /dev/null
+++ b/src/crepe/Collider.h
@@ -0,0 +1,14 @@
+#pragma once
+
+#include "Component.h"
+
+namespace crepe {
+
+class Collider : public Component {
+public:
+	Collider(int size);
+
+	int size;
+};
+
+} // namespace crepe
diff --git a/src/crepe/Component.cpp b/src/crepe/Component.cpp
new file mode 100644
index 0000000..d14159c
--- /dev/null
+++ b/src/crepe/Component.cpp
@@ -0,0 +1,5 @@
+#include "Component.h"
+
+using namespace crepe;
+
+Component::Component() : active(true) {}
diff --git a/src/crepe/Component.h b/src/crepe/Component.h
new file mode 100644
index 0000000..16a4ce5
--- /dev/null
+++ b/src/crepe/Component.h
@@ -0,0 +1,14 @@
+#pragma once
+
+namespace crepe {
+
+class Component {
+public:
+	Component();
+	// TODO: shouldn't this constructor be deleted because this class will never
+	// directly be instantiated?
+
+	bool active;
+};
+
+} // namespace crepe
diff --git a/src/crepe/ComponentManager.cpp b/src/crepe/ComponentManager.cpp
new file mode 100644
index 0000000..9a3fec7
--- /dev/null
+++ b/src/crepe/ComponentManager.cpp
@@ -0,0 +1,24 @@
+#include "ComponentManager.h"
+
+using namespace crepe;
+
+ComponentManager & ComponentManager::get_instance() {
+	static ComponentManager instance;
+	return instance;
+}
+
+void ComponentManager::delete_all_components_of_id(uint32_t id) {
+	// Loop through all the types (in the unordered_map<>)
+	for (auto & [type, componentArray] : components) {
+		// Make sure that the id (that we are looking for) is within the boundaries of the vector<>
+		if (id < componentArray.size()) {
+			// Clear the components at this specific id
+			componentArray[id].clear();
+		}
+	}
+}
+
+void ComponentManager::delete_all_components() {
+	// Clear the whole unordered_map<>
+	components.clear();
+}
diff --git a/src/crepe/ComponentManager.h b/src/crepe/ComponentManager.h
new file mode 100644
index 0000000..2ab9dc8
--- /dev/null
+++ b/src/crepe/ComponentManager.h
@@ -0,0 +1,62 @@
+#pragma once
+
+#include <cstdint>
+#include <memory>
+#include <typeindex>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
+#include "Component.h"
+
+namespace crepe {
+
+class ComponentManager {
+public:
+	// Singleton
+	static ComponentManager & get_instance();
+	ComponentManager(const ComponentManager &) = delete;
+	ComponentManager(ComponentManager &&) = delete;
+	ComponentManager & operator=(const ComponentManager &) = delete;
+	ComponentManager & operator=(ComponentManager &&) = delete;
+
+public:
+	//! Add a component of a specific type
+	template <typename T, typename... Args>
+	void add_component(uint32_t id, Args &&... args);
+	//! Deletes all components of a specific type and id
+	template <typename T>
+	void delete_components_by_id(uint32_t id);
+	//! Deletes all components of a specific type
+	template <typename T>
+	void delete_components();
+	//! Deletes all components of a specific id
+	void delete_all_components_of_id(uint32_t id);
+	//! Deletes all components
+	void delete_all_components();
+
+	//! Get a vector<> of all components at specific type and id
+	template <typename T>
+	std::vector<std::reference_wrapper<T>>
+	get_components_by_id(uint32_t id) const;
+	//! Get a vector<> of all components of a specific type
+	template <typename T>
+	std::vector<std::reference_wrapper<T>> get_components_by_type() const;
+
+private:
+	ComponentManager() = default;
+
+	/*
+	 * The std::unordered_map<std::type_index, std::vector<std::vector<std::unique_ptr<Component>>>> below might seem a bit strange, let me explain this structure:
+	 * The std::unordered_map<> has a key and value. The key is a std::type_index and the value is a std::vector. So, a new std::vector will be created for each new std::type_index.
+	 * The first std::vector<> stores another vector<>. This first vector<> is to bind the entity's id to a component.
+	 * The second std::vector<> stores unique_ptrs. Each component can be gathered via an unique_ptr. This second vector<> allows multiple components of the same std::type_index for one entity (id).
+	 */
+	std::unordered_map<std::type_index,
+					   std::vector<std::vector<std::unique_ptr<Component>>>>
+		components;
+};
+
+} // namespace crepe
+
+#include "ComponentManager.hpp"
diff --git a/src/crepe/ComponentManager.hpp b/src/crepe/ComponentManager.hpp
new file mode 100644
index 0000000..084cd33
--- /dev/null
+++ b/src/crepe/ComponentManager.hpp
@@ -0,0 +1,152 @@
+#pragma once
+
+#include <type_traits>
+
+#include "ComponentManager.h"
+
+namespace crepe {
+
+template <class T, typename... Args>
+void ComponentManager::add_component(uint32_t id, Args &&... args) {
+	using namespace std;
+
+	static_assert(is_base_of<Component, T>::value, "add_component must recieve a derivative class of Component");
+
+	// Determine the type of T (this is used as the key of the unordered_map<>)
+	type_index type = typeid(T);
+
+	// Check if this component type is already in the unordered_map<>
+	if (components.find(type) == components.end()) {
+		//If not, create a new (empty) vector<> of vector<unique_ptr<Component>>
+		components[type] = vector<vector<unique_ptr<Component>>>();
+	}
+
+	// Resize the vector<> if the id is greater than the current size
+	if (id >= components[type].size()) {
+		// Initialize new slots to nullptr (resize does automatically init to nullptr)
+		components[type].resize(id + 1);
+	}
+
+	// Create a new component of type T (arguments directly forwarded). The
+	// constructor must be called by ComponentManager.
+	T * instance = new T(forward<Args>(args)...);
+	// store its unique_ptr in the vector<>
+	components[type][id].push_back(unique_ptr<T>(instance));
+}
+
+template <typename T>
+void ComponentManager::delete_components_by_id(uint32_t id) {
+	using namespace std;
+
+	// Determine the type of T (this is used as the key of the unordered_map<>)
+	type_index type = typeid(T);
+
+	// Find the type (in the unordered_map<>)
+	if (components.find(type) != components.end()) {
+		// Get the correct vector<>
+		vector<vector<unique_ptr<Component>>> & component_array
+			= components[type];
+
+		// Make sure that the id (that we are looking for) is within the boundaries of the vector<>
+		if (id < component_array.size()) {
+			// Clear the whole vector<> of this specific type and id
+			component_array[id].clear();
+		}
+	}
+}
+
+template <typename T>
+void ComponentManager::delete_components() {
+	// Determine the type of T (this is used as the key of the unordered_map<>)
+	std::type_index type = typeid(T);
+
+	// Find the type (in the unordered_map<>)
+	if (components.find(type) != components.end()) {
+		// Clear the whole vector<> of this specific type
+		components[type].clear();
+	}
+}
+
+template <typename T>
+std::vector<std::reference_wrapper<T>>
+ComponentManager::get_components_by_id(uint32_t id) const {
+	using namespace std;
+
+	// Determine the type of T (this is used as the key of the unordered_map<>)
+	type_index type = typeid(T);
+
+	// Create an empty vector<>
+	vector<reference_wrapper<T>> component_vector;
+
+	// Find the type (in the unordered_map<>)
+	if (components.find(type) != components.end()) {
+		// Get the correct vector<>
+		const vector<vector<unique_ptr<Component>>> & component_array
+			= components.at(type);
+
+		// Make sure that the id (that we are looking for) is within the boundaries of the vector<>
+		if (id < component_array.size()) {
+			// Loop trough the whole vector<>
+			for (const unique_ptr<Component> & component_ptr :
+				 component_array[id]) {
+				// Cast the unique_ptr to a raw pointer
+				T * casted_component = static_cast<T *>(component_ptr.get());
+
+				// Ensure that the cast was successful
+				if (casted_component) {
+					// Add the dereferenced raw pointer to the vector<>
+					component_vector.push_back(*casted_component);
+				}
+			}
+		}
+	}
+
+	// Return the vector<>
+	return component_vector;
+}
+
+template <typename T>
+std::vector<std::reference_wrapper<T>>
+ComponentManager::get_components_by_type() const {
+	using namespace std;
+
+	// Determine the type of T (this is used as the key of the unordered_map<>)
+	type_index type = typeid(T);
+
+	// Create an empty vector<>
+	vector<reference_wrapper<T>> component_vector;
+	// Set the id to 0 (the id will also be stored in the returned vector<>)
+	// uint32_t id = 0;
+
+	// Find the type (in the unordered_map<>)
+	if (components.find(type) != components.end()) {
+
+		// Get the correct vector<>
+		const vector<vector<unique_ptr<Component>>> & component_array
+			= components.at(type);
+
+		// Loop through the whole vector<>
+		for (const vector<unique_ptr<Component>> & component :
+			 component_array) {
+			// Loop trough the whole vector<>
+			for (const unique_ptr<Component> & component_ptr : component) {
+				// Cast the unique_ptr to a raw pointer
+				T * casted_component = static_cast<T *>(component_ptr.get());
+
+				// Ensure that the cast was successful
+				if (casted_component) {
+					// Pair the dereferenced raw pointer and the id and add it to the vector<>
+					component_vector.emplace_back(ref(*casted_component));
+				}
+			}
+
+			// Increase the id (the id will also be stored in the returned vector<>)
+			//++id;
+		}
+	}
+
+	// Return the vector<>
+	return component_vector;
+}
+
+} // namespace crepe
diff --git a/src/crepe/GameObject.cpp b/src/crepe/GameObject.cpp
new file mode 100644
index 0000000..de3beb6
--- /dev/null
+++ b/src/crepe/GameObject.cpp
@@ -0,0 +1,7 @@
+#include "GameObject.h"
+
+using namespace crepe;
+
+GameObject::GameObject(uint32_t id, std::string name, std::string tag,
+					   int layer)
+	: id(id), name(name), tag(tag), active(true), layer(layer) {}
diff --git a/src/crepe/GameObject.h b/src/crepe/GameObject.h
new file mode 100644
index 0000000..3588d9a
--- /dev/null
+++ b/src/crepe/GameObject.h
@@ -0,0 +1,24 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+
+namespace crepe {
+
+class GameObject {
+public:
+	GameObject(uint32_t id, std::string name, std::string tag, int layer);
+
+	template <typename T, typename... Args>
+	void add_component(Args &&... args);
+
+	uint32_t id;
+	std::string name;
+	std::string tag;
+	bool active;
+	int layer;
+};
+
+} // namespace crepe
+
+#include "GameObject.hpp"
diff --git a/src/crepe/GameObject.hpp b/src/crepe/GameObject.hpp
new file mode 100644
index 0000000..5966fbf
--- /dev/null
+++ b/src/crepe/GameObject.hpp
@@ -0,0 +1,15 @@
+#pragma once
+
+#include "GameObject.h"
+
+#include "ComponentManager.h"
+
+namespace crepe {
+
+template <typename T, typename... Args>
+void GameObject::add_component(Args &&... args) {
+	auto & mgr = ComponentManager::get_instance();
+	mgr.add_component<T>(id, std::forward<Args>(args)...);
+}
+
+} // namespace crepe
diff --git a/src/crepe/Rigidbody.cpp b/src/crepe/Rigidbody.cpp
new file mode 100644
index 0000000..495d908
--- /dev/null
+++ b/src/crepe/Rigidbody.cpp
@@ -0,0 +1,6 @@
+#include "Rigidbody.h"
+
+using namespace crepe;
+
+Rigidbody::Rigidbody(int mass, int gravityScale, int bodyType)
+	: mass(mass), gravity_scale(gravityScale), body_type(bodyType) {}
diff --git a/src/crepe/Rigidbody.h b/src/crepe/Rigidbody.h
new file mode 100644
index 0000000..63a8877
--- /dev/null
+++ b/src/crepe/Rigidbody.h
@@ -0,0 +1,16 @@
+#pragma once
+
+#include "Component.h"
+
+namespace crepe {
+
+class Rigidbody : public Component {
+public:
+	Rigidbody(int mass, int gravityScale, int bodyType);
+
+	int mass;
+	int gravity_scale;
+	int body_type;
+};
+
+} // namespace crepe
diff --git a/src/crepe/Script.cpp b/src/crepe/Script.cpp
new file mode 100644
index 0000000..42e3666
--- /dev/null
+++ b/src/crepe/Script.cpp
@@ -0,0 +1,7 @@
+#include "Script.h"
+
+using namespace crepe;
+
+void Script::init() { }
+void Script::update() { }
+
diff --git a/src/crepe/Script.h b/src/crepe/Script.h
new file mode 100644
index 0000000..ba4073a
--- /dev/null
+++ b/src/crepe/Script.h
@@ -0,0 +1,16 @@
+#pragma once
+
+namespace crepe {
+
+class Script {
+protected:
+	virtual void init();
+	virtual void update();
+	// NOTE: additional *events* (like unity's OnDisable and OnEnable) should be
+	// implemented as member methods in derivative user script classes and
+	// registered in init(), otherwise this class will balloon in size with each
+	// added event.
+};
+
+}
+
diff --git a/src/crepe/ScriptSystem.cpp b/src/crepe/ScriptSystem.cpp
new file mode 100644
index 0000000..e301c71
--- /dev/null
+++ b/src/crepe/ScriptSystem.cpp
@@ -0,0 +1,22 @@
+#include "util/log.h"
+
+#include "ScriptSystem.h"
+
+using namespace crepe;
+
+ScriptSystem::ScriptSystem() {
+	dbg_trace();
+}
+ScriptSystem::~ScriptSystem() {
+	dbg_trace();
+}
+
+ScriptSystem & ScriptSystem::get_instance() {
+	static ScriptSystem instance;
+	return instance;
+}
+
+void ScriptSystem::update() {
+	dbg_trace();
+}
+
diff --git a/src/crepe/ScriptSystem.h b/src/crepe/ScriptSystem.h
new file mode 100644
index 0000000..e1ed290
--- /dev/null
+++ b/src/crepe/ScriptSystem.h
@@ -0,0 +1,18 @@
+#pragma once
+
+#include "System.h"
+
+namespace crepe {
+
+class ScriptSystem : public System {
+public:
+	static ScriptSystem & get_instance();
+	virtual void update();
+
+private:
+	ScriptSystem();
+	~ScriptSystem();
+};
+
+}
+
diff --git a/src/crepe/Sound.h b/src/crepe/Sound.h
index 1ac20a7..b7cfbb8 100644
--- a/src/crepe/Sound.h
+++ b/src/crepe/Sound.h
@@ -1,7 +1,7 @@
 #pragma once
 
-#include <soloud.h>
-#include <soloud_wav.h>
+#include <soloud/soloud.h>
+#include <soloud/soloud_wav.h>
 
 #include <memory>
 
diff --git a/src/crepe/SoundContext.h b/src/crepe/SoundContext.h
index 090966d..d3123d2 100644
--- a/src/crepe/SoundContext.h
+++ b/src/crepe/SoundContext.h
@@ -1,6 +1,6 @@
 #pragma once
 
-#include <soloud.h>
+#include <soloud/soloud.h>
 
 #include "Sound.h"
 
diff --git a/src/crepe/Sprite.cpp b/src/crepe/Sprite.cpp
new file mode 100644
index 0000000..a5a5e68
--- /dev/null
+++ b/src/crepe/Sprite.cpp
@@ -0,0 +1,8 @@
+#include <string>
+
+#include "Sprite.h"
+
+using namespace crepe;
+using namespace std;
+
+Sprite::Sprite(string path) : path(path) {}
diff --git a/src/crepe/Sprite.h b/src/crepe/Sprite.h
new file mode 100644
index 0000000..143e702
--- /dev/null
+++ b/src/crepe/Sprite.h
@@ -0,0 +1,16 @@
+#pragma once
+
+#include <string>
+
+#include "Component.h"
+
+namespace crepe {
+
+class Sprite : public Component {
+public:
+	Sprite(std::string path);
+
+	std::string path;
+};
+
+} // namespace crepe
diff --git a/src/crepe/System.h b/src/crepe/System.h
new file mode 100644
index 0000000..3fe3d66
--- /dev/null
+++ b/src/crepe/System.h
@@ -0,0 +1,23 @@
+#pragma once
+
+namespace crepe {
+
+class System {
+public:
+	static System & get_instance();
+	virtual void update() = 0;
+
+protected:
+	System() { };
+	virtual ~System() { };
+
+private:
+	// singleton
+	System(const System &) = delete;
+	System(System &&) = delete;
+	System & operator=(const System &) = delete;
+	System & operator=(System &&) = delete;
+};
+
+}
+
diff --git a/src/crepe/api/BehaviorScript.cpp b/src/crepe/api/BehaviorScript.cpp
new file mode 100644
index 0000000..2dd933e
--- /dev/null
+++ b/src/crepe/api/BehaviorScript.cpp
@@ -0,0 +1,10 @@
+#include "../util/log.h"
+
+#include "BehaviorScript.h"
+
+using namespace crepe::api;
+
+BehaviorScript::BehaviorScript() {
+	dbg_trace();
+}
+
diff --git a/src/crepe/api/BehaviorScript.h b/src/crepe/api/BehaviorScript.h
new file mode 100644
index 0000000..e9542c1
--- /dev/null
+++ b/src/crepe/api/BehaviorScript.h
@@ -0,0 +1,17 @@
+#pragma once
+
+#include "../Script.h"
+#include "../Component.h"
+
+namespace crepe::api {
+
+class BehaviorScript : public Script, public Component {
+	// only allow ComponentManager to instantiate scripts
+	friend class ComponentManager;
+
+protected:
+	BehaviorScript();
+};
+
+}
+
diff --git a/src/crepe/api/CMakeLists.txt b/src/crepe/api/CMakeLists.txt
index 9548594..86623de 100644
--- a/src/crepe/api/CMakeLists.txt
+++ b/src/crepe/api/CMakeLists.txt
@@ -1,9 +1,10 @@
 target_sources(crepe PUBLIC
 	# AudioSource.cpp
+	BehaviorScript.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
-	AudioSource.h
-	Component.h
+	# AudioSource.h
+	BehaviorScript.h
 )
 
diff --git a/src/crepe/api/Component.h b/src/crepe/api/Component.h
deleted file mode 100644
index d5e0499..0000000
--- a/src/crepe/api/Component.h
+++ /dev/null
@@ -1,10 +0,0 @@
-#pragma once
-
-namespace crepe::api {
-
-class Component {
-public:
-	bool active;
-};
-
-} // namespace crepe::api
diff --git a/src/crepe/util/log.cpp b/src/crepe/util/log.cpp
index 6829ec3..f91d52c 100644
--- a/src/crepe/util/log.cpp
+++ b/src/crepe/util/log.cpp
@@ -8,10 +8,10 @@
 using namespace crepe::util;
 
 static const char * const LOG_PREFIX[] = {
-	[log_level::debug] = "[DBG] ",
-	[log_level::info] = "[INFO] ",
-	[log_level::warning] = "[WARN] ",
-	[log_level::error] = "[ERR] ",
+	[log_level::DEBUG] = "[DBG] ",
+	[log_level::INFO] = "[INFO] ",
+	[log_level::WARNING] = "[WARN] ",
+	[log_level::ERROR] = "[ERR] ",
 };
 
 static void va_logf(enum log_level level, va_list args, const std::string fmt) {
@@ -38,7 +38,7 @@ static void va_logf(enum log_level level, va_list args, const std::string fmt) {
 void crepe::util::logf(const char * fmt, ...) {
 	va_list args;
 	va_start(args, fmt);
-	va_logf(crepe::util::log_level::debug, args, fmt);
+	va_logf(crepe::util::log_level::DEBUG, args, fmt);
 	va_end(args);
 }
 
diff --git a/src/crepe/util/log.h b/src/crepe/util/log.h
index bfe7291..2b0fbe1 100644
--- a/src/crepe/util/log.h
+++ b/src/crepe/util/log.h
@@ -7,7 +7,7 @@
 
 // utility macros
 #define _crepe_logf_here(fmt, ...) \
-	crepe::util::logf(util::log_level::debug, "%s%s (%s:%d)" fmt "\n", \
+	crepe::util::logf(util::log_level::DEBUG, "%s%s (%s:%d)" fmt "\n", \
 					  crepe::util::color::FG_WHITE, __PRETTY_FUNCTION__, \
 					  __FILE_NAME__, __LINE__, crepe::util::color::RESET, \
 					  __VA_ARGS__)
@@ -24,10 +24,10 @@
 namespace crepe::util {
 
 enum log_level {
-	debug,
-	info,
-	warning,
-	error,
+	DEBUG,
+	INFO,
+	WARNING,
+	ERROR,
 };
 
 void logf(const char * fmt, ...);
diff --git a/src/example/CMakeLists.txt b/src/example/CMakeLists.txt
index bcc9271..6df4ce7 100644
--- a/src/example/CMakeLists.txt
+++ b/src/example/CMakeLists.txt
@@ -1,3 +1,18 @@
-add_executable(audio_internal EXCLUDE_FROM_ALL audio_internal.cpp)
-target_link_libraries(audio_internal PUBLIC crepe)
+# add_example(target_name [SOURCES...])
+function(add_example target_name)
+	# if SOURCES is not specified
+	if(NOT ARGV1)
+		# A .cpp file with target_name exists, and should be used
+		set(sources ${target_name}.cpp)
+	else()
+		set(sources ${ARGV})
+	endif()
+
+	add_executable(${target_name} EXCLUDE_FROM_ALL ${sources})
+	target_link_libraries(${target_name} PUBLIC crepe)
+endfunction()
+
+add_example(audio_internal)
+add_example(components_internal)
+add_example(script)
 
diff --git a/src/example/components_internal.cpp b/src/example/components_internal.cpp
new file mode 100644
index 0000000..54ce295
--- /dev/null
+++ b/src/example/components_internal.cpp
@@ -0,0 +1,60 @@
+/** \file
+ * 
+ * Standalone example for usage of the internal ECS
+ */
+
+#include <cassert>
+#include <chrono>
+
+#include <crepe/Collider.h>
+#include <crepe/Component.h>
+#include <crepe/ComponentManager.h>
+#include <crepe/GameObject.h>
+#include <crepe/Rigidbody.h>
+#include <crepe/Sprite.h>
+#include <crepe/util/log.h>
+
+using namespace crepe;
+using namespace std;
+
+#define OBJ_COUNT 100000
+
+int main() {
+	dbg_trace();
+
+	auto & mgr = ComponentManager::get_instance();
+
+	auto start_adding = chrono::high_resolution_clock::now();
+
+	GameObject * game_object[OBJ_COUNT];
+
+	for (int i = 0; i < OBJ_COUNT; ++i) {
+		game_object[i] = new GameObject(i, "Name", "Tag", 0);
+
+		game_object[i]->add_component<Sprite>("test");
+		game_object[i]->add_component<Rigidbody>(0, 0, i);
+		game_object[i]->add_component<Collider>(i);
+	}
+
+	auto stop_adding = chrono::high_resolution_clock::now();
+
+	auto sprites = mgr.get_components_by_type<Sprite>();
+	for (auto sprite : sprites) {
+		assert(sprite.get().path == "test");
+	}
+
+	auto stop_looping = chrono::high_resolution_clock::now();
+
+	for (int i = 0; i < OBJ_COUNT; ++i) {
+		delete game_object[i];
+	}
+
+	auto add_time = chrono::duration_cast<chrono::microseconds>(stop_adding
+																- start_adding);
+	auto loop_time = chrono::duration_cast<chrono::microseconds>(stop_looping
+																 - stop_adding);
+	printf("add time:  %ldus\n", add_time.count());
+	printf("loop time: %ldus\n", loop_time.count());
+
+	return 0;
+}
diff --git a/src/example/script.cpp b/src/example/script.cpp
new file mode 100644
index 0000000..28605c7
--- /dev/null
+++ b/src/example/script.cpp
@@ -0,0 +1,33 @@
+/** \file
+ * 
+ * Standalone example for usage of the script component and system
+ */
+
+#include <crepe/util/log.h>
+#include <crepe/ScriptSystem.h>
+#include <crepe/ComponentManager.h>
+#include <crepe/GameObject.h>
+
+#include <crepe/api/BehaviorScript.h>
+
+using namespace crepe;
+using namespace std;
+
+class MyScript : public api::BehaviorScript {
+	void update() {
+		dbg_trace();
+	}
+};
+
+int main() {
+	dbg_trace();
+
+	auto obj = GameObject(0, "name", "tag", 0);
+	obj.add_component<MyScript>();
+
+	auto & sys = ScriptSystem::get_instance();
+	sys.update(); // -> MyScript::update
+
+	return 0;
+}
+
diff --git a/src/readme.md b/src/readme.md
index 1c5d3a2..a4a71e7 100644
--- a/src/readme.md
+++ b/src/readme.md
@@ -2,7 +2,32 @@
 
 This folder contains the crêpe engine source files, unit tests, and some toy
 examples. The only target built by default by the CMakeLists.txt in this folder
-is the crêpe shared library object. Unit tests can be built by explicitly
-specifying the target `test_main` when running the build command. Each source
-file in the example/ folder corresponds to a CMake target as well.
+is the crêpe shared library object.
+
+Examples (using Ninja):
+
+```
+$ cmake -B build -G Ninja
+$ ninja -C build
+```
+
+Unit tests can be built by explicitly specifying the target `test_main` when
+running the build command:
+
+```
+$ ninja -C build test_main
+```
+
+Each source file in the example/ folder corresponds to a CMake target as well:
+
+```
+$ ninja -C build audio_internal components_internal
+```
+
+For installing crêpe system-wide after building (install must be run with
+elevated privileges):
+
+```
+# ninja -C build install
+```