example_game.cpp

This example shows a basic game project consisting of a single source file. The main application class, ExampleGame, is defined at the top while the main function is defined at the bottom.

This can be used to study how various libdonut features are combined to form a working application. Note however that for a real project, the code that this example represents would typically be split across multiple files to make the main application file less cluttered.

The game uses the included examples/data/ folder as its main resource directory for all asset files that are loaded at runtime.

 
#include <donut/aliases.hpp>
#include <donut/donut.hpp>
 
#include <array>         // std::array
#include <charconv>      // std::from_chars_result, std::from_chars
#include <chrono>        // std::chrono_literals
#include <concepts>      // std::integral
#include <cstddef>       // std::size_t, std::byte, std::max_align_t
#include <cstdio>        // stderr, std::sscanf, std::fprintf
#include <cstdlib>       // EXIT_SUCCESS, EXIT_FAILURE
#include <exception>     // std::exception
#include <fmt/format.h>  // fmt::format
#include <forward_list>  // std::forward_list
#include <optional>      // std::optional
#include <span>          // std::span
#include <stdexcept>     // std::runtime_error
#include <string>        // std::string
#include <string_view>   // std::string_view
#include <system_error>  // std::errc
#include <unordered_map> // std::unordered_map
 
namespace {
 
struct GameOptions {
    app::ApplicationOptions applicationOptions{
        .tickRate = 30.0f,
        .maxFrameRate = 240.0f,
    };
    gfx::WindowOptions windowOptions{
        .title = "Example Game",
        .size{640, 480},
        .resizable = true,
    };
    const char* mainMenuMusicFilepath = "sounds/music/donauwalzer.ogg";
    float fieldOfView = 90.0f;
};
 
class ExampleGame final : public app::Application {
public:
    ExampleGame(Filesystem& filesystem, const GameOptions& options)
        : app::Application(options.applicationOptions)
        , window(options.windowOptions)
        , testTexture(gfx::Image{filesystem, "textures/test.png"})
        , circleTexture(gfx::Image{filesystem, "textures/circle.png"}, {.useLinearFiltering = false, .useMipmap = false})
        , carrotCakeModel(filesystem, "models/carrot_cake.obj")
        , testSprite(spriteAtlas.insert(renderer, gfx::Image{filesystem, "textures/test.png"}))
        , testSubSprite(spriteAtlas.createSubSprite(testSprite, 200, 200, 100, 100, gfx::SpriteAtlas::FLIP_HORIZONTALLY))
        , mainFont(filesystem, "fonts/unscii/unscii-8.ttf")
        , verticalFieldOfView(2.0f * atan((3.0f / 4.0f) * tan(radians(options.fieldOfView) * 0.5f))) {
        loadBindingsConfiguration(filesystem, "configuration/bindings.json");
 
        initializeSoundStage();
        playMainMenuMusic(filesystem, options.mainMenuMusicFilepath);
 
        loadCircles();
 
        resize();
    }
 
protected:
    void update(app::FrameInfo frameInfo) override {
        using namespace std::chrono_literals;
 
        handleEvents();
 
        if (soundStage) {
            soundStage->update(frameInfo.deltaTime, listener);
        }
 
        if (inputManager.justPressed(events::Input::KEY_F10)) {
            quit();
        }
 
        if (inputManager.justPressed(events::Input::KEY_F11) ||
            (inputManager.justPressed(events::Input::KEY_RETURN) && (inputManager.isPressed(events::Input::KEY_LALT) || inputManager.isPressed(events::Input::KEY_RALT)))) {
            window.setFullscreen(!window.isFullscreen());
        }
 
        if (inputManager.justPressed(events::Input::KEY_F2)) {
            if (soundStage) {
                soundStage->stopSound(musicId);
            }
        }
 
        const float sprintInput = (inputManager.isPressed(Action::SPRINT)) ? 4.0f : 1.0f;
 
        vec2 movementInput = inputManager.getAbsoluteValue(Action::MOVE_LEFT, Action::MOVE_RIGHT, Action::MOVE_DOWN, Action::MOVE_UP);
        if (const float movementInputLengthSquared = length2(movementInput); movementInputLengthSquared > 1.0f) {
            movementInput /= sqrt(movementInputLengthSquared);
        }
        const float carrotCakeSpeed = 2.0f * sprintInput;
        carrotCakeVelocity = {movementInput * carrotCakeSpeed, 0.0f};
 
        if (inputManager.isPressed(Action::CONFIRM)) {
            const vec2 aimInput = inputManager.getRelativeValue(Action::AIM_LEFT, Action::AIM_RIGHT, Action::AIM_DOWN, Action::AIM_UP);
            carrotCakeScale = clamp(carrotCakeScale + aimInput * 10.0f, 0.25f, 4.0f);
        }
 
        const float scrollInput = inputManager.getRelativeValue(Action::SCROLL_DOWN, Action::SCROLL_UP);
        carrotCakeCurrentPosition.z -= scrollInput * 0.25f * sprintInput;
 
        const bool triggerInput = inputManager.isPressed(Action::CANCEL);
        counterA += timerA.countUpLoop(frameInfo.deltaTime, 1s, triggerInput);
        counterB += timerB.countDownLoop(frameInfo.deltaTime, 1s, triggerInput);
    }
 
    void tick(app::TickInfo tickInfo) override {
        carrotCakePreviousPosition = carrotCakeCurrentPosition;
        carrotCakeCurrentPosition += carrotCakeVelocity * tickInfo.tickInterval;
    }
 
    void display(app::TickInfo /*tickInfo*/, app::FrameInfo frameInfo) override {
        carrotCakeDisplayPosition = mix(carrotCakePreviousPosition, carrotCakeCurrentPosition, frameInfo.tickInterpolationAlpha);
 
        uploadShaderData(frameInfo);
 
        gfx::Framebuffer& framebuffer = window.getFramebuffer();
 
        renderer.clearFramebufferColorAndDepth(framebuffer, Color::PURPLE * 0.25f);
 
        alignas(std::max_align_t) std::array<std::byte, 1024> renderPassStorage;
 
        {
            gfx::RenderPass renderPass{renderPassStorage};
            drawWorld3D(renderPass, frameInfo);
            renderer.render(framebuffer, renderPass, worldViewport, worldCamera);
        }
 
        {
            gfx::RenderPass renderPass{renderPassStorage};
            drawWorld2D(renderPass, frameInfo);
            renderer.render(framebuffer, renderPass, screenViewport, screenCamera, worldScissor);
        }
 
        {
            gfx::RenderPass renderPass{renderPassStorage};
            drawUserInterface(renderPass, frameInfo);
            drawFrameRateCounter(renderPass);
            renderer.render(framebuffer, renderPass, screenViewport, screenCamera);
        }
 
        window.present();
    }
 
private:
    enum class Action {
        CONFIRM,
        CANCEL,
        MOVE_UP,
        MOVE_DOWN,
        MOVE_LEFT,
        MOVE_RIGHT,
        AIM_UP,
        AIM_DOWN,
        AIM_LEFT,
        AIM_RIGHT,
        SPRINT,
        ATTACK,
        SCROLL_UP,
        SCROLL_DOWN,
    };
 
    struct ExampleShader2D : gfx::Shader2D {
        static constexpr const char* FRAGMENT_SHADER_SOURCE_CODE = R"GLSL(
            in vec2 fragmentTextureCoordinates;
            in vec4 fragmentTintColor;
 
            out vec4 outputColor;
 
            uniform sampler2D textureUnit;
            uniform float time;
 
            void main() {
                outputColor = fragmentTintColor * vec4(0.5 + 0.5 * cos(time), 0.5 + 0.5 * sin(time), 0.5 + 0.5 * sin(time + 1.5), 1.0) * texture(textureUnit, fragmentTextureCoordinates);
            }
        )GLSL";
 
        ExampleShader2D()
            : gfx::Shader2D({
                  .vertexShaderSourceCode = gfx::Shader2D::VERTEX_SHADER_SOURCE_CODE_INSTANCED_TEXTURED_QUAD,
                  .fragmentShaderSourceCode = FRAGMENT_SHADER_SOURCE_CODE,
              }) {}
 
        void setTime(float elapsedTime) {
            program.setUniformFloat(time, elapsedTime);
        }
 
    private:
        gfx::ShaderParameter time{program, "time"};
    };
 
    struct ExampleShader3D : gfx::Shader3D {
        struct PointLight {
            vec3 position;
            vec3 ambient;
            vec3 diffuse;
            vec3 specular;
            float constantFalloff;
            float linearFalloff;
            float quadraticFalloff;
        };
 
        struct PointLightParameters {
            PointLightParameters(const gfx::ShaderProgram& program, const char* name)
                : position(program, fmt::format("{}.position", name).c_str())
                , ambient(program, fmt::format("{}.ambient", name).c_str())
                , diffuse(program, fmt::format("{}.diffuse", name).c_str())
                , specular(program, fmt::format("{}.specular", name).c_str())
                , constantFalloff(program, fmt::format("{}.constantFalloff", name).c_str())
                , linearFalloff(program, fmt::format("{}.linearFalloff", name).c_str())
                , quadraticFalloff(program, fmt::format("{}.quadraticFalloff", name).c_str()) {}
 
            gfx::ShaderParameter position;
            gfx::ShaderParameter ambient;
            gfx::ShaderParameter diffuse;
            gfx::ShaderParameter specular;
            gfx::ShaderParameter constantFalloff;
            gfx::ShaderParameter linearFalloff;
            gfx::ShaderParameter quadraticFalloff;
        };
 
        static constexpr std::size_t POINT_LIGHT_COUNT = 4;
        static constexpr const char* FRAGMENT_SHADER_SOURCE_CODE = R"GLSL(
            #ifndef GAMMA
            #define GAMMA 2.2
            #endif
 
            struct PointLight {
                vec3 position;
                vec3 ambient;
                vec3 diffuse;
                vec3 specular;
                float constantFalloff;
                float linearFalloff;
                float quadraticFalloff;
            };
 
            in vec3 fragmentPosition;
            in vec3 fragmentNormal;
            in vec3 fragmentTangent;
            in vec3 fragmentBitangent;
            in vec2 fragmentTextureCoordinates;
            in vec4 fragmentTintColor;
            in vec3 fragmentSpecularFactor;
            in vec3 fragmentEmissiveFactor;
 
            out vec4 outputColor;
 
            uniform sampler2D diffuseMap;
            uniform sampler2D specularMap;
            uniform sampler2D normalMap;
            uniform sampler2D emissiveMap;
            uniform vec3 diffuseColor;
            uniform vec3 specularColor;
            uniform vec3 normalScale;
            uniform vec3 emissiveColor;
            uniform float specularExponent;
            uniform float dissolveFactor;
            uniform float occlusionFactor;
 
            uniform PointLight pointLights[POINT_LIGHT_COUNT];
            uniform vec3 viewPosition;
            uniform sampler2D tintTexture;
 
            float lambert(float cosine) {
                return max(cosine, 0.0);
            }
 
            float blinnPhong(vec3 normal, vec3 lightDirection, vec3 viewDirection) {
                vec3 halfwayDirection = normalize(lightDirection + viewDirection);
                return pow(max(dot(normal, halfwayDirection), 0.0), specularExponent);
            }
 
            vec3 calculatePointLight(PointLight light, vec3 normal, vec3 viewDirection, vec3 ambient, vec3 diffuse, vec3 specular) {
                vec3 lightDifference = light.position - fragmentPosition;
                float lightDistanceSquared = dot(lightDifference, lightDifference);
                float lightDistance = sqrt(lightDistanceSquared);
                vec3 lightDirection = lightDifference * (1.0 / lightDistance);
                float cosine = dot(normal, lightDirection);
                float diffuseFactor = lambert(cosine);
                float specularFactor = blinnPhong(normal, lightDirection, viewDirection);
                float attenuation = 1.0 / (light.constantFalloff + light.linearFalloff * lightDistance + light.quadraticFalloff * lightDistanceSquared);
                vec3 ambientTerm = light.ambient * ambient;
                vec3 diffuseTerm = light.diffuse * diffuseFactor * diffuse;
                vec3 specularTerm = light.specular * specularFactor * specular;
                const float visibility = 1.0;
                return attenuation * (ambientTerm * occlusionFactor + (diffuseTerm + specularTerm) * visibility);
            }
 
            vec3 tonemap(vec3 color) {
                return color / (color + vec3(1.0));
            }
 
            void main() {
                vec4 sampledDiffuse = texture(diffuseMap, fragmentTextureCoordinates);
                vec4 diffuse = fragmentTintColor * vec4(diffuseColor, 1.0 - dissolveFactor) * vec4(pow(sampledDiffuse.rgb, vec3(GAMMA)), sampledDiffuse.a);
                vec3 specular = fragmentSpecularFactor * specularColor * texture(specularMap, fragmentTextureCoordinates).rgb;
                vec3 emissive = fragmentEmissiveFactor * emissiveColor * texture(emissiveMap, fragmentTextureCoordinates).rgb;
 
                mat3 TBN = mat3(normalize(fragmentTangent), normalize(fragmentBitangent), normalize(fragmentNormal));
                vec3 surfaceNormal = normalScale * (texture(normalMap, fragmentTextureCoordinates).xyz * 2.0 - vec3(1.0));
                vec3 normal = normalize(TBN * surfaceNormal);
 
                vec3 viewDirection = normalize(viewPosition - fragmentPosition);
 
                vec3 color = emissive;
                for (uint i = uint(0); i < uint(POINT_LIGHT_COUNT); ++i) {
                    color += calculatePointLight(pointLights[i], normal, viewDirection, vec3(1.0), diffuse.rgb, specular);
                }
 
                color *= texture(tintTexture, fragmentTextureCoordinates).rgb;
 
                outputColor = vec4(pow(tonemap(color), vec3(1.0 / GAMMA)), diffuse.a);
            }
        )GLSL";
 
        ExampleShader3D()
            : gfx::Shader3D({
                  .definitions = fmt::format("#define POINT_LIGHT_COUNT {}", POINT_LIGHT_COUNT).c_str(),
                  .vertexShaderSourceCode = gfx::Shader3D::VERTEX_SHADER_SOURCE_CODE_INSTANCED_MODEL,
                  .fragmentShaderSourceCode = FRAGMENT_SHADER_SOURCE_CODE,
              }) {}
 
        void setPointLights(std::span<const PointLight, POINT_LIGHT_COUNT> values) {
            for (std::size_t i = 0; i < POINT_LIGHT_COUNT; ++i) {
                program.setUniformVec3(pointLights[i].position, values[i].position);
                program.setUniformVec3(pointLights[i].ambient, values[i].ambient);
                program.setUniformVec3(pointLights[i].diffuse, values[i].diffuse);
                program.setUniformVec3(pointLights[i].specular, values[i].specular);
                program.setUniformFloat(pointLights[i].constantFalloff, values[i].constantFalloff);
                program.setUniformFloat(pointLights[i].linearFalloff, values[i].linearFalloff);
                program.setUniformFloat(pointLights[i].quadraticFalloff, values[i].quadraticFalloff);
            }
        }
 
        void setViewPosition(vec3 position) {
            program.setUniformVec3(viewPosition, position);
        }
 
        void setTintTexture(const gfx::Texture* texture) {
            program.setUniformSampler(tintTexture, texture);
        }
 
    private:
        gfx::ShaderArray<PointLightParameters, POINT_LIGHT_COUNT> pointLights{program, "pointLights"};
        gfx::ShaderParameter viewPosition{program, "viewPosition"};
        gfx::ShaderParameter tintTexture{program, "tintTexture"};
    };
 
    void resize() {
        constexpr ivec2 RENDER_RESOLUTION{640, 480};
        constexpr ivec2 WORLD_VIEWPORT_POSITION{15, 15};
        constexpr ivec2 WORLD_VIEWPORT_SIZE{380, 450};
 
        const ivec2 size = window.getDrawableSize();
 
        const auto [viewport, scale] = gfx::Viewport::createIntegerScaled(size, RENDER_RESOLUTION);
        screenViewport = viewport;
        screenCamera = gfx::Camera::createOrthographic({
            .offset{0.0f, 0.0f},
            .size = RENDER_RESOLUTION,
        });
 
        worldViewport = {
            .position = screenViewport.position + WORLD_VIEWPORT_POSITION * scale,
            .size = WORLD_VIEWPORT_SIZE * scale,
        };
        worldScissor = {.position = worldViewport.position, .size = worldViewport.size};
        worldCamera = gfx::Camera::createPerspective({
            .verticalFieldOfView = verticalFieldOfView,
            .aspectRatio = static_cast<float>(worldViewport.size.x) / static_cast<float>(worldViewport.size.y),
            .nearZ = 0.1f,
            .farZ = 100.0f,
        });
    }
 
    void loadBindingsConfiguration(const Filesystem& filesystem, const char* filepath) {
        const std::unordered_map<std::string_view, Action> actionsByIdentifier{
            {"confirm", Action::CONFIRM},
            {"cancel", Action::CANCEL},
            {"move_up", Action::MOVE_UP},
            {"move_down", Action::MOVE_DOWN},
            {"move_left", Action::MOVE_LEFT},
            {"move_right", Action::MOVE_RIGHT},
            {"aim_up", Action::AIM_UP},
            {"aim_down", Action::AIM_DOWN},
            {"aim_left", Action::AIM_LEFT},
            {"aim_right", Action::AIM_RIGHT},
            {"sprint", Action::SPRINT},
            {"attack", Action::ATTACK},
            {"scroll_up", Action::SCROLL_UP},
            {"scroll_down", Action::SCROLL_DOWN},
        };
 
        try {
            json::StringParser{filesystem.openFile(filepath).readAllIntoString()}.parseObject(
                json::onProperty([&](const json::SourceLocation&, const json::String& key, json::StringParser& parser) -> void {
                    if (const events::Input input = events::findInput(key); input != events::Input::UNKNOWN) {
                        const auto bindAction = [&](const json::SourceLocation&, const json::String& value) -> void {
                            if (const auto it = actionsByIdentifier.find(value); it != actionsByIdentifier.end()) {
                                inputManager.addBinding(input, it->second);
                            } else {
                                throw std::runtime_error{fmt::format("Invalid action identifier \"{}\".", value)};
                            }
                        };
                        parser.parseValue(json::onArray([&](const json::SourceLocation&, json::StringParser& parser) -> void { parser.parseArray(json::onString(bindAction)); }) |
                                          json::onString(bindAction));
                    } else {
                        throw std::runtime_error{fmt::format("Invalid input identifier \"{}\".", key)};
                    }
                }));
        } catch (const json::Error& e) {
            throw std::runtime_error{fmt::format("{}:{}:{}: {}", filepath, e.source.lineNumber, e.source.columnNumber, e.what())};
        } catch (const std::exception& e) {
            throw std::runtime_error{fmt::format("{}: {}", filepath, e.what())};
        }
    }
 
    void initializeSoundStage() {
        try {
            soundStage.emplace();
        } catch (const audio::Error& e) {
            // Don't crash on failure, since the user might just not have a working sound card.
            // Just print an error message instead.
            std::fprintf(stderr, "%s\n", e.what());
        }
    }
 
    void playMainMenuMusic(const Filesystem& filesystem, const char* filepath) {
        using namespace std::chrono_literals;
 
        if (soundStage) {
            if (filesystem.fileExists(filepath)) {
                music.emplace(filesystem, filepath,
                    audio::SoundOptions{
                        .attenuationModel = audio::SoundAttenuationModel::NO_ATTENUATION,
                        .volume = 0.1f,
                        .listenerRelative = true,
                        .looping = true,
                    });
                musicId = soundStage->createPausedSoundInBackground(*music);
                soundStage->seekToSoundTime(musicId, 46700ms);
                soundStage->resumeSound(musicId);
            }
        }
    }
 
    void loadCircles() {
        constexpr Circle<float> CIRCLE_A{.center{60.0f, 80.0f}, .radius = 20.0f};
        constexpr Circle<float> CIRCLE_B{.center{50.0f, 90.0f}, .radius = 20.0f};
        constexpr Circle<float> CIRCLE_C{.center{60.0f, 120.0f}, .radius = 20.0f};
        constexpr Circle<float> CIRCLE_D{.center{300.0f, 100.0f}, .radius = 10.0f};
        constexpr Circle<float> CIRCLE_E{.center{200.0f, 180.0f}, .radius = 30.0f};
        constexpr Circle<float> CIRCLE_F{.center{140.0f, 440.0f}, .radius = 20.0f};
        quadtree[getAabbOf(CIRCLE_A)].push_front(CIRCLE_A);
        quadtree[getAabbOf(CIRCLE_B)].push_front(CIRCLE_B);
        quadtree[getAabbOf(CIRCLE_C)].push_front(CIRCLE_C);
        quadtree[getAabbOf(CIRCLE_D)].push_front(CIRCLE_D);
        quadtree[getAabbOf(CIRCLE_E)].push_front(CIRCLE_E);
        quadtree[getAabbOf(CIRCLE_F)].push_front(CIRCLE_F);
    }
 
    void handleEvents() {
        inputManager.prepareForEvents();
        for (const events::Event& event : eventPump.pollEvents()) {
            if (event.is<events::ApplicationQuitRequestedEvent>()) {
                quit();
            } else if (event.is<events::WindowSizeChangedEvent>()) {
                resize();
            }
            inputManager.handleEvent(event);
        }
    }
 
    void uploadShaderData(app::FrameInfo frameInfo) {
        const ExampleShader3D::PointLight baseLight = {
            .position = carrotCakeDisplayPosition,
            .ambient{0.001f, 0.001f, 0.001f},
            .diffuse{0.5f + 0.5f * sin(frameInfo.elapsedTime), 0.8f, 0.8f},
            .specular{0.8f, 0.8f, 0.8f},
            .constantFalloff = 1.0f,
            .linearFalloff = 0.04f,
            .quadraticFalloff = 0.03f,
        };
 
        const auto baseLightWithOffset = [&](vec3 offset) -> ExampleShader3D::PointLight {
            ExampleShader3D::PointLight result = baseLight;
            result.position += offset;
            return result;
        };
 
        const std::array<ExampleShader3D::PointLight, ExampleShader3D::POINT_LIGHT_COUNT> pointLights{{
            baseLightWithOffset({-2.0f, 0.0f, 0.0f}),
            baseLightWithOffset({0.0f, -2.0f, 0.0f}),
            baseLightWithOffset({0.0f, 2.0f, 0.0f}),
            baseLightWithOffset({0.0f, 0.0f, 2.0f}),
        }};
 
        const vec3 viewPosition{0.0f, 0.0f, 0.0f};
 
        exampleShader2D.setTime(frameInfo.elapsedTime);
 
        exampleShader3D.setPointLights(pointLights);
        exampleShader3D.setViewPosition(viewPosition);
        exampleShader3D.setTintTexture(&testTexture);
    }
 
    void drawWorld3D(gfx::RenderPass& renderPass, const app::FrameInfo& frameInfo) {
        constexpr vec3 BACKGROUND_OFFSET{0.0f, 3.5f, -10.0f};
        constexpr vec2 BACKGROUND_SCALE{9.0f, 9.0f};
        constexpr float BACKGROUND_ANGLE = -30.0f;
        constexpr float BACKGROUND_SPEED = 2.0f;
 
        renderPass.draw(gfx::ModelInstance{
            .shader = &exampleShader3D,
            .model = gfx::Model::QUAD,
            .diffuseMapOverride = &testTexture,
            .transformation = translate(BACKGROUND_OFFSET) *                            //
                              orientate4(vec3{radians(BACKGROUND_ANGLE), 0.0f, 0.0f}) * //
                              scale(vec3{BACKGROUND_SCALE, 1.0f}),
            .textureOffset{0.0f, frameInfo.elapsedTime * BACKGROUND_SPEED},
            .textureScale = 1000.0f * BACKGROUND_SCALE / testTexture.getSize2D(),
        });
 
        renderPass.draw(gfx::ModelInstance{
            .shader = &exampleShader3D,
            .model = &carrotCakeModel,
            .transformation = translate(vec3{-0.6f, 0.2f, -3.0f}) *                                                //
                              scale(vec3{5.0f, 5.0f, 5.0f}) *                                                      //
                              orientate4(vec3{0.0f, frameInfo.elapsedTime * 1.5f, frameInfo.elapsedTime * 2.0f}) * //
                              translate(vec3{0.0f, -0.05f, 0.0f}),
        });
 
        renderPass.draw(gfx::ModelInstance{
            .shader = &exampleShader3D,
            .model = &carrotCakeModel,
            .transformation = translate(vec3{-0.5f, -2.0f, -5.0f}) *                                               //
                              scale(vec3{5.0f, 5.0f, 5.0f}) *                                                      //
                              orientate4(vec3{frameInfo.elapsedTime * 2.0f, frameInfo.elapsedTime * 1.5f, 0.0f}) * //
                              translate(vec3{0.0f, -0.05f, 0.0f}),
        });
 
        renderPass.draw(gfx::ModelInstance{
            .model = gfx::Model::CUBE,
            .transformation = translate(vec3{1.0f, -1.0f, -5.0f}) * //
                              scale(vec3{0.5f, 0.5, 0.5f}) *        //
                              orientate4(vec3{frameInfo.elapsedTime * 2.0f, frameInfo.elapsedTime * 1.5f, 0.0f}),
            .tintColor = Color::RED,
        });
 
        renderPass.draw(gfx::ModelInstance{
            .model = &carrotCakeModel,
            .transformation = translate(vec3{0.6f, 0.7f, -3.0f} + carrotCakeDisplayPosition) *                     //
                              scale(vec3{5.0f * carrotCakeScale.x, 5.0f * carrotCakeScale.y, 5.0f}) *              //
                              orientate4(vec3{0.0f, frameInfo.elapsedTime * 1.5f, frameInfo.elapsedTime * 2.0f}) * //
                              translate(vec3{0.0f, -0.05f, 0.0f}),
        });
    }
 
    void drawWorld2D(gfx::RenderPass& renderPass, const app::FrameInfo& frameInfo) {
        renderPass.draw(gfx::RectangleInstance{
            .shader = &exampleShader2D,
            .texture = &testTexture,
            .position{40.0f, 370.0f},
            .size{180.0f, 70.0f},
            .angle = frameInfo.elapsedTime,
            .origin{0.5f, 0.5f},
            .tintColor{1.0f, 1.0f, 1.0f, 0.2f},
        });
 
        renderPass.draw(gfx::RectangleInstance{
            .texture = &testTexture,
            .position{100.0f, 380.0f},
            .size{180.0f, 70.0f},
            .angle = frameInfo.elapsedTime,
            .origin{0.5f, 0.5f},
        });
 
        renderPass.draw(gfx::RectangleInstance{
            .shader = &exampleShader2D,
            .texture = &testTexture,
            .position{160.0f, 390.0f},
            .size{180.0f, 70.0f},
            .angle = frameInfo.elapsedTime,
            .origin{0.5f, 0.5f},
            .tintColor{1.0f, 1.0f, 1.0f, 0.2f},
        });
    }
 
    void drawUserInterface(gfx::RenderPass& renderPass, const app::FrameInfo& frameInfo) {
        renderPass.draw(gfx::TextureInstance{
            .texture = &testTexture,
            .position{200.0f + cos(frameInfo.elapsedTime) * 50.0f, 120.0f + sin(frameInfo.elapsedTime) * 50.0f},
            .scale{0.2f + sin(frameInfo.elapsedTime) * 0.1f, 0.2f + cos(frameInfo.elapsedTime) * 0.1f},
            .origin{0.5f, 0.5f},
        });
 
        renderPass.draw(gfx::SpriteInstance{
            .atlas = &spriteAtlas,
            .id = testSprite,
            .position{450.0f + cos(frameInfo.elapsedTime) * 50.0f, 120.0f + sin(frameInfo.elapsedTime) * 50.0f},
            .scale{0.2f + sin(frameInfo.elapsedTime) * 0.1f, 0.2f + cos(frameInfo.elapsedTime) * 0.1f},
            .origin{0.5f, 0.5f},
        });
 
        renderPass.draw(gfx::SpriteInstance{
            .atlas = &spriteAtlas,
            .id = testSubSprite,
            .position{450.0f + cos(frameInfo.elapsedTime) * 50.0f, 320.0f + sin(frameInfo.elapsedTime) * 50.0f},
            .scale{0.2f + sin(frameInfo.elapsedTime) * 0.1f, 0.2f + cos(frameInfo.elapsedTime) * 0.1f},
            .origin{0.5f, 0.5f},
        });
 
        renderPass.draw(gfx::TextInstance{
            .text = &longTestText,
            .position{410.0f, 416.0f},
            .color = Color::LIME,
        });
 
        temporaryText.reshape(mainFont, 8,
            fmt::format("Position:\n({:.2f}, {:.2f}, {:.2f})\n\nScale:\n({:.2f}, {:.2f})", carrotCakeDisplayPosition.x, carrotCakeDisplayPosition.y, carrotCakeDisplayPosition.z,
                carrotCakeScale.x, carrotCakeScale.y));
 
        renderPass.draw(gfx::TextCopyInstance{
            .text = &temporaryText,
            .position{410.0f, 310.0f},
        });
 
        if (inputManager.isPressed(Action::MOVE_UP) || inputManager.justPressed(Action::MOVE_UP)) {
            renderPass.draw(gfx::TextInstance{.text = &upArrowText, .position{590.0f, 320.0f}});
        }
        if (inputManager.isPressed(Action::MOVE_DOWN) || inputManager.justPressed(Action::MOVE_DOWN)) {
            renderPass.draw(gfx::TextInstance{.text = &downArrowText, .position{590.0f, 300.0f}});
        }
        if (inputManager.isPressed(Action::MOVE_LEFT) || inputManager.justPressed(Action::MOVE_LEFT)) {
            renderPass.draw(gfx::TextInstance{.text = &leftArrowText, .position{580.0f, 310.0f}});
        }
        if (inputManager.isPressed(Action::MOVE_RIGHT) || inputManager.justPressed(Action::MOVE_RIGHT)) {
            renderPass.draw(gfx::TextInstance{.text = &rightArrowText, .position{600.0f, 310.0f}});
        }
 
        if (inputManager.isPressed(Action::AIM_UP) || inputManager.justPressed(Action::AIM_UP)) {
            renderPass.draw(gfx::TextInstance{.text = &upArrowText, .position{590.0f, 280.0f}});
        }
        if (inputManager.isPressed(Action::AIM_DOWN) || inputManager.justPressed(Action::AIM_DOWN)) {
            renderPass.draw(gfx::TextInstance{.text = &downArrowText, .position{590.0f, 260.0f}});
        }
        if (inputManager.isPressed(Action::AIM_LEFT) || inputManager.justPressed(Action::AIM_LEFT)) {
            renderPass.draw(gfx::TextInstance{.text = &leftArrowText, .position{580.0f, 270.0f}});
        }
        if (inputManager.isPressed(Action::AIM_RIGHT) || inputManager.justPressed(Action::AIM_RIGHT)) {
            renderPass.draw(gfx::TextInstance{.text = &rightArrowText, .position{600.0f, 270.0f}});
        }
 
        renderPass.draw(gfx::TextStringInstance{
            .font = &mainFont,
            .characterSize = 8,
            .position{410.0f, 240.0f},
            .string =
                fmt::format("Timer   A: {:.2f}\nCounter A: {}\n\nTimer   B: {:.2f}\nCounter B: {}", static_cast<float>(timerA), counterA, static_cast<float>(timerB), counterB),
        });
 
        if (inputManager.isPressed(events::Input::KEY_SPACE)) {
            constexpr Capsule<2, float> STATIC_CAPSULE{.centerLine{.pointA{80.0f, 80.0f}, .pointB{300.0f, 200.0f}}, .radius = 50.0f};
            constexpr vec2 STATIC_CAPSULE_VECTOR = STATIC_CAPSULE.centerLine.pointB - STATIC_CAPSULE.centerLine.pointA;
            const Circle<float> movingCircle{.center = vec2{200.0f, 50.0f} + vec2{carrotCakeDisplayPosition} * 50.0f, .radius = 32.0f};
            const Color movingCircleColor = (intersects(movingCircle, STATIC_CAPSULE)) ? Color::RED : Color::YELLOW;
 
            renderPass.draw(gfx::RectangleInstance{
                .texture = &circleTexture,
                .position = STATIC_CAPSULE.centerLine.pointA,
                .size{STATIC_CAPSULE.radius * 2.0f, STATIC_CAPSULE.radius * 2.0f},
                .origin{0.5f, 0.5f},
                .tintColor = Color::GREEN,
            });
            renderPass.draw(gfx::RectangleInstance{
                .texture = &circleTexture,
                .position = STATIC_CAPSULE.centerLine.pointB,
                .size{STATIC_CAPSULE.radius * 2.0f, STATIC_CAPSULE.radius * 2.0f},
                .origin{0.5f, 0.5f},
                .tintColor = Color::GREEN,
            });
            renderPass.draw(gfx::RectangleInstance{
                .position = STATIC_CAPSULE.centerLine.pointA,
                .size{length(STATIC_CAPSULE_VECTOR), STATIC_CAPSULE.radius * 2.0f},
                .angle = static_cast<float>(atan2(STATIC_CAPSULE_VECTOR.y, STATIC_CAPSULE_VECTOR.x)),
                .origin{0.0f, 0.5f},
                .tintColor = Color::GREEN,
            });
 
            renderPass.draw(gfx::RectangleInstance{
                .texture = &circleTexture,
                .position = movingCircle.center,
                .size{movingCircle.radius * 2.0f, movingCircle.radius * 2.0f},
                .origin{0.5f, 0.5f},
                .tintColor = movingCircleColor,
            });
 
            const auto drawBorder = [&](const Box<2, float>& box, float lineThickness, Color color) -> void {
                const vec2 extent = box.max - box.min;
                renderPass.draw(gfx::RectangleInstance{.position = box.min, .size{extent.x, lineThickness}, .origin{0.0f, 0.0f}, .tintColor = color});
                renderPass.draw(gfx::RectangleInstance{.position{box.min.x, box.max.y}, .size{extent.x, lineThickness}, .origin{0.0f, 1.0f}, .tintColor = color});
                renderPass.draw(gfx::RectangleInstance{.position = box.min, .size{lineThickness, extent.y}, .origin{0.0f, 0.0f}, .tintColor = color});
                renderPass.draw(gfx::RectangleInstance{.position{box.max.x, box.min.y}, .size{lineThickness, extent.y}, .origin{1.0f, 0.0f}, .tintColor = color});
            };
 
            quadtree.traverseActiveNodes([&](const Box<2, float>& looseBounds, const std::forward_list<Circle<float>>* circles) -> void {
                drawBorder(looseBounds, 2.0f, Color::BLANCHED_ALMOND);
                if (circles) {
                    for (const Circle<float>& circle : *circles) {
                        renderPass.draw(gfx::RectangleInstance{
                            .texture = &circleTexture,
                            .position = circle.center,
                            .size{circle.radius * 2.0f, circle.radius * 2.0f},
                            .origin{0.5f, 0.5f},
                            .tintColor = Color::BLUE,
                        });
                    }
                }
            });
            const Box<2, float> movingCircleAabb = getAabbOf(movingCircle);
            std::size_t aabbTestCount = 0;
            std::size_t circleTestCount = 0;
            quadtree.traverseActiveNodes(
                [&](const Box<2, float>& looseBounds, const std::forward_list<Circle<float>>* circles) -> void {
                    drawBorder(looseBounds, 2.0f, Color::DARK_BLUE);
                    if (circles) {
                        for (const Circle<float>& circle : *circles) {
                            ++circleTestCount;
                            if (intersects(circle, movingCircle)) {
                                renderPass.draw(gfx::RectangleInstance{
                                    .texture = &circleTexture,
                                    .position = circle.center,
                                    .size{circle.radius * 2.0f, circle.radius * 2.0f},
                                    .origin{0.5f, 0.5f},
                                    .tintColor = Color::DARK_GOLDEN_ROD,
                                });
                            }
                        }
                    }
                },
                [&](const Box<2, float>& looseBounds) -> bool {
                    ++aabbTestCount;
                    return intersects(movingCircleAabb, looseBounds);
                });
 
            renderPass.draw(gfx::TextStringInstance{
                .font = &mainFont,
                .characterSize = 8,
                .position{410.0f, 450.0f},
                .color = Color::BURLY_WOOD,
                .string = fmt::format("AABB tests: {}\nCircle tests: {}", aabbTestCount, circleTestCount),
            });
        }
 
        if (inputManager.justReleased(events::Input::KEY_SPACE)) {
            inputManager.resetAllInputs();
        }
    }
 
    void drawFrameRateCounter(gfx::RenderPass& renderPass) {
        const unsigned fps = getLastSecondFrameCount();
        temporaryText.reshape(mainFont, 8, fmt::format("FPS: {}", fps), {0.0f, 0.0f}, {2.0f, 2.0f});
        const vec2 fpsPosition{15.0f + 2.0f, 480.0f - 15.0f - 20.0f};
        const Color fpsColor = (fps < 60) ? Color::RED : (fps < 120) ? Color::YELLOW : (fps < 240) ? Color::GRAY : Color::LIME;
        renderPass.draw(gfx::TextCopyInstance{.text = &temporaryText, .position = fpsPosition + vec2{1.0f, -1.0f}, .color = Color::BLACK});
        renderPass.draw(gfx::TextCopyInstance{.text = &temporaryText, .position = fpsPosition, .color = fpsColor});
    }
 
    events::EventPump eventPump{};
    gfx::Window window;
    gfx::Renderer renderer{};
    gfx::Viewport screenViewport{};
    gfx::Viewport worldViewport{};
    Rectangle<int> worldScissor{};
    gfx::Camera screenCamera{};
    gfx::Camera worldCamera{};
    audio::Listener listener{};
    gfx::SpriteAtlas spriteAtlas{};
    gfx::Texture testTexture;
    gfx::Texture circleTexture;
    gfx::Model carrotCakeModel;
    gfx::SpriteAtlas::SpriteId testSprite;
    gfx::SpriteAtlas::SpriteId testSubSprite;
    gfx::Font mainFont;
    gfx::Text longTestText{mainFont, 8,
        "The quick brown fox\n"
        "jumps over the lazy dog\n"
        "\n"
        "FLYGANDE BÄCKASINER SÖKA\n"
        "HWILA PÅ MJUKA TUVOR QXZ\n"
        "0123456789\n"
        "\n"
        "+!\"#%&/()=?`@${[]}\\\n"
        "~\'<>|,.-;:_"};
    gfx::Text upArrowText{mainFont, 8, "^"};
    gfx::Text downArrowText{mainFont, 8, "v"};
    gfx::Text leftArrowText{mainFont, 8, "<"};
    gfx::Text rightArrowText{mainFont, 8, ">"};
    gfx::Text temporaryText{};
    ExampleShader2D exampleShader2D{};
    ExampleShader3D exampleShader3D{};
    events::InputManager inputManager{};
    std::optional<audio::SoundStage> soundStage{};
    std::optional<audio::Sound> music{};
    audio::SoundStage::SoundInstanceId musicId{};
    float verticalFieldOfView;
    vec3 carrotCakeCurrentPosition{0.0f, 0.0f, 0.0f};
    vec3 carrotCakePreviousPosition{0.0f, 0.0f, 0.0f};
    vec3 carrotCakeDisplayPosition{0.0f, 0.0f, 0.0f};
    vec2 carrotCakeScale{1.0f, 1.0f};
    vec3 carrotCakeVelocity{0.0f, 0.0f, 0.0f};
    Time<float> timerA{};
    Time<float> timerB{};
    std::size_t counterA = 0;
    std::size_t counterB = 0;
    LooseQuadtree<std::forward_list<Circle<float>>> quadtree{
        Box<2, float>{.min{15.0f, 15.0f}, .max{15.0f + 380.0f, 15.0f + 450.0f}},
        vec2{32.0f, 32.0f},
    };
};
 
class OptionsParser {
public:
    OptionsParser(int argc, char* argv[]) noexcept
        : argumentCount(argc)
        , arguments(argv) {
        assert(argc > 0);
    }
 
    [[nodiscard]] Variant<GameOptions, std::string> parseGameOptions() {
        GameOptions options{};
        while (argumentIndex < argumentCount) {
            const std::string_view argument{arguments[argumentIndex]};
            if (argument == "-help" || argument == "--help" || argument == "-?" || argument == "/?") {
                return "Options:\n"
                       "  -help                        Show this information.\n"
                       "  -title <string>              Title of the main window.\n"
                       "  -width <pixels>              Width of the main window.\n"
                       "  -height <pixels>             Height of the main window.\n"
                       "  -resizable                   Enable window resizing.\n"
                       "  -fullscreen                  Enable fullscreen.\n"
                       "  -vsync                       Enable vertical synchronization.\n"
                       "  -min-fps <Hz>                Minimum frame rate before slowdown.\n"
                       "  -max-fps <Hz>                Frame rate limit. 0 = unlimited.\n"
                       "  -msaa <level>                Level of multisample anti-aliasing.\n"
                       "  -main-menu-music <filepath>  Music file to use for the main menu.\n"
                       "  -fov <degrees>               Field of view for world rendering.";
            }
 
            if (argument == "-title") {
                parseOptionValue("title", options.windowOptions.title);
            } else if (argument == "-width") {
                parseOptionValue("width", options.windowOptions.size.x);
            } else if (argument == "-height") {
                parseOptionValue("height", options.windowOptions.size.y);
            } else if (argument == "-resizable") {
                parseOptionValue("resizable", options.windowOptions.resizable);
            } else if (argument == "-fullscreen") {
                parseOptionValue("fullscreen", options.windowOptions.fullscreen);
            } else if (argument == "-vsync") {
                parseOptionValue("vsync", options.windowOptions.vSync);
            } else if (argument == "-min-fps") {
                parseOptionValue("min fps", options.applicationOptions.minFrameRate);
            } else if (argument == "-max-fps") {
                parseOptionValue("max fps", options.applicationOptions.maxFrameRate);
            } else if (argument == "-msaa") {
                parseOptionValue("msaa", options.windowOptions.msaaLevel);
            } else if (argument == "-main-menu-music") {
                parseOptionValue("main menu music file", options.mainMenuMusicFilepath);
            } else if (argument == "-fov") {
                parseOptionValue("fov", options.fieldOfView);
            } else {
                throw std::runtime_error{fmt::format("Unknown option {}. Try -help.", argument)};
            }
            ++argumentIndex;
        }
        return options;
    }
 
private:
    void parseOptionValue(std::string_view optionName, const char*& output) {
        if (++argumentIndex >= argumentCount) {
            throw std::runtime_error{fmt::format("Missing {} value.", optionName)};
        }
        output = arguments[argumentIndex];
    }
 
    void parseOptionValue(std::string_view optionName, std::integral auto& output) {
        if (++argumentIndex >= argumentCount) {
            throw std::runtime_error{fmt::format("Missing {} value.", optionName)};
        }
        const std::string_view string{arguments[argumentIndex]};
        if (const std::from_chars_result result = std::from_chars(string.data(), string.data() + string.size(), output); result.ec != std::errc{}) {
            throw std::runtime_error{fmt::format("Invalid {} value \"{}\": {}", optionName, string, std::make_error_code(result.ec).message())};
        }
    }
 
    void parseOptionValue(std::string_view optionName, float& output) {
        if (++argumentIndex >= argumentCount) {
            throw std::runtime_error{fmt::format("Missing {} value.", optionName)};
        }
        if (std::sscanf(arguments[argumentIndex], "%f", &output) != 1) {
            throw std::runtime_error{fmt::format("Invalid {} value \"{}\".", optionName, arguments[argumentIndex])};
        }
    }
 
    void parseOptionValue(std::string_view /*optionName*/, bool& output) {
        output = true;
    }
 
    const int argumentCount;
    char** const arguments;
    int argumentIndex = 1;
};
 
} // namespace
 
int main(int argc, char* argv[]) {
    try {
        Filesystem filesystem{argv[0],
            FilesystemOptions{
                .organizationName = "Donut",
                .applicationName = "ExampleGame",
                .dataDirectory = "data",
                .archiveSearchPath = ".",
                .archiveSearchFileExtension = "pk3",
            }};
 
        const Variant<GameOptions, std::string> options = OptionsParser{argc, argv}.parseGameOptions();
        if (options.is<std::string>()) {
            std::fprintf(stderr, "%s\n", options.as<std::string>().c_str());
            return EXIT_SUCCESS;
        }
 
        ExampleGame game{filesystem, options.as<GameOptions>()};
 
        game.run();
    } catch (const std::exception& e) {
        std::fprintf(stderr, "%s\n", e.what());
        events::MessageBox::show(events::MessageBox::Type::ERROR_MESSAGE, "Error", e.what());
        return EXIT_FAILURE;
    }
    return EXIT_SUCCESS;
}