fix

Firmware/main/src/app_main.cpp

@@ -4,6 +4,7 @@
 #include "cardboy/apps/gameboy_app.hpp"
 #include "cardboy/apps/menu_app.hpp"
 #include "cardboy/apps/settings_app.hpp"
+#include "cardboy/apps/snake_app.hpp"
 #include "cardboy/apps/tetris_app.hpp"
 #include "cardboy/backend/esp_backend.hpp"
 #include "cardboy/sdk/app_system.hpp"
@@ -234,6 +235,7 @@ extern "C" void app_main() {
     system.registerApp(apps::createMenuAppFactory());
     system.registerApp(apps::createSettingsAppFactory());
     system.registerApp(apps::createClockAppFactory());
+    system.registerApp(apps::createSnakeAppFactory());
     system.registerApp(apps::createTetrisAppFactory());
     system.registerApp(apps::createGameboyAppFactory());
 

Firmware/sdk/apps/CMakeLists.txt

@@ -16,4 +16,5 @@ add_subdirectory(menu)
 add_subdirectory(clock)
 add_subdirectory(settings)
 add_subdirectory(gameboy)
+add_subdirectory(snake)
 add_subdirectory(tetris)

Firmware/sdk/apps/gameboy/src/gameboy_app.cpp

@@ -299,6 +299,9 @@ public:
                     break;
                 }
 
+                if (mode != Mode::Running)
+                    break;
+
 
                 GB_PERF_ONLY(perf.geometryUs = 0;)
 
@@ -306,11 +309,49 @@ public:
                 gb_run_frame(&gb);
                 GB_PERF_ONLY(perf.runUs = nowMicros() - runStartUs;)
 
+                {
+                    uint32_t freqHz = 0;
+                    uint8_t  loud   = 0;
+                    if (apu.computeEffectiveTone(freqHz, loud)) {
+                        // Basic smoothing: if freq didn't change much, keep it; otherwise snap quickly
+                        const uint32_t prev = lastFreqHz;
+                        if (prev != 0 && freqHz != 0) {
+                            const uint32_t diff = (prev > freqHz) ? (prev - freqHz) : (freqHz - prev);
+                            if (diff < 15) {
+                                freqHz = prev; // minor jitter suppression
+                                ++stableFrames;
+                            } else {
+                                stableFrames = 0;
+                            }
+                        } else {
+                            stableFrames = 0;
+                        }
+                        lastFreqHz           = freqHz;
+                        lastLoud             = loud;
+                        const uint32_t durMs = 16;
+                        playTone(freqHz, durMs, 0);
+                    } else {
+                        lastFreqHz = 0;
+                        lastLoud   = 0;
+                        // Don't enqueue anything; queue naturally drains and buzzer stops
+                    }
+                }
+
                 GB_PERF_ONLY(const uint64_t renderStartUs = nowMicros();)
                 renderGameFrame();
                 GB_PERF_ONLY(perf.renderUs = nowMicros() - renderStartUs;)
                 break;
             }
+            case Mode::Prompt: {
+                GB_PERF_ONLY(const uint64_t handleStartUs = nowMicros();)
+                handlePromptInput(input);
+                GB_PERF_ONLY(perf.handleUs = nowMicros() - handleStartUs;)
+
+                GB_PERF_ONLY(const uint64_t renderStartUs = nowMicros();)
+                renderPrompt();
+                GB_PERF_ONLY(perf.renderUs = nowMicros() - renderStartUs;)
+                break;
+            }
         }
 
         prevInput = input;
@@ -777,8 +818,9 @@ public:
         }
     };
 
-    enum class Mode { Browse, Running };
+    enum class Mode { Browse, Running, Prompt };
     enum class ScaleMode { Original, FullHeight, FullHeightWide };
+    enum class PromptKind { None, LoadState, SaveState };
 
     struct PerfTracker {
         enum class CallbackKind { RomRead, CartRamRead, CartRamWrite, LcdDraw, Error };
@@ -905,8 +947,19 @@ public:
 
         void printStep(Mode stepMode, bool gbReady, bool frameDirty, uint32_t fps, const std::string& romName,
                        std::size_t romCount, std::size_t selectedIdx, bool browserDirty) const {
-            auto              toMs    = [](uint64_t us) { return static_cast<double>(us) / 1000.0; };
-            const char*       modeStr = (stepMode == Mode::Running) ? "RUN" : "BROWSE";
+            auto        toMs    = [](uint64_t us) { return static_cast<double>(us) / 1000.0; };
+            const char* modeStr = "UNKNOWN";
+            switch (stepMode) {
+                case Mode::Running:
+                    modeStr = "RUN";
+                    break;
+                case Mode::Browse:
+                    modeStr = "BROWSE";
+                    break;
+                case Mode::Prompt:
+                    modeStr = "PROMPT";
+                    break;
+            }
             const char*       name    = romName.empty() ? "-" : romName.c_str();
             const std::size_t safeIdx = (romCount == 0) ? 0 : std::min(selectedIdx, romCount - 1);
             std::printf(
@@ -1085,6 +1138,10 @@ public:
     uint32_t             fpsCurrent        = 0;
     std::string          activeRomName;
     std::string          activeRomSavePath;
+    std::string          activeRomStatePath;
+    PromptKind           promptKind      = PromptKind::None;
+    int                  promptSelection = 0; // 0 = Yes, 1 = No
+    bool                 promptDirty     = false;
     SimpleApu            apu{};
     // Smoothing state for buzzer tone
     uint32_t lastFreqHz   = 0;
@@ -1423,21 +1480,25 @@ public:
             return false;
         }
 
-        gb.direct.priv   = this;
-        gb.direct.joypad = 0xFF;
-
         gb_init_lcd(&gb, &GameboyApp::lcdDrawLine);
+        applyRuntimeBindings();
 
+        gb.direct.joypad     = 0xFF;
         gb.direct.interlace  = false;
         gb.direct.frame_skip = true;
 
         const uint_fast32_t saveSize = gb_get_save_size(&gb);
         cartRam.assign(static_cast<std::size_t>(saveSize), 0);
         std::string savePath;
+        std::string statePath;
         const bool  fsReady = (filesystem && filesystem->isMounted()) || ensureFilesystemReady();
-        if (fsReady)
-            savePath = buildSavePath(rom, romDirectory());
-        activeRomSavePath = savePath;
+        if (fsReady) {
+            const std::string romDir = romDirectory();
+            savePath                 = buildSavePath(rom, romDir);
+            statePath                = buildStatePath(rom, romDir);
+        }
+        activeRomSavePath  = savePath;
+        activeRomStatePath = statePath;
         loadSaveFile();
 
         resetFpsStats();
@@ -1452,6 +1513,10 @@ public:
         if (!fsReady)
             statusText.append(" (no save)");
         setStatus(std::move(statusText));
+
+        if (stateFileExists())
+            enterPrompt(PromptKind::LoadState);
+
         return true;
     }
 
@@ -1464,6 +1529,10 @@ public:
             cartRam.clear();
             activeRomName.clear();
             activeRomSavePath.clear();
+            activeRomStatePath.clear();
+            promptKind      = PromptKind::None;
+            promptSelection = 0;
+            promptDirty     = false;
             return;
         }
 
@@ -1477,6 +1546,10 @@ public:
         cartRam.clear();
         activeRomName.clear();
         activeRomSavePath.clear();
+        activeRomStatePath.clear();
+        promptKind      = PromptKind::None;
+        promptSelection = 0;
+        promptDirty     = false;
         std::memset(&gb, 0, sizeof(gb));
         apu.reset();
         mode         = Mode::Browse;
@@ -1491,6 +1564,19 @@ public:
         if (scaleToggleCombo)
             toggleScaleMode();
 
+        const bool exitComboPressed     = input.start && input.select;
+        const bool exitComboJustPressed = exitComboPressed && !(prevInput.start && prevInput.select);
+        if (exitComboJustPressed) {
+            if (!activeRomStatePath.empty()) {
+                enterPrompt(PromptKind::SaveState);
+            } else {
+                unloadRom();
+                setStatus("Save state unavailable");
+            }
+            gb.direct.joypad = 0xFF;
+            return;
+        }
+
         uint8_t joypad = 0xFF;
         if (input.a)
             joypad &= ~JOYPAD_A;
@@ -1510,13 +1596,6 @@ public:
             joypad &= ~JOYPAD_RIGHT;
 
         gb.direct.joypad = joypad;
-
-        const bool exitComboPressed     = input.start && input.select;
-        const bool exitComboJustPressed = exitComboPressed && !(prevInput.start && prevInput.select);
-        if (exitComboJustPressed) {
-            setStatus("Saved " + activeRomName);
-            unloadRom();
-        }
     }
 
     void renderGameFrame() {
@@ -1688,6 +1767,186 @@ public:
         }
     }
 
+    void applyRuntimeBindings() {
+        gb.gb_cart_ram_read      = &GameboyApp::cartRamRead;
+        gb.gb_cart_ram_write     = &GameboyApp::cartRamWrite;
+        gb.gb_error              = &GameboyApp::errorCallback;
+        gb.display.lcd_draw_line = &GameboyApp::lcdDrawLine;
+        gb.direct.priv           = this;
+        if (romDataView)
+            gb.direct.rom = romDataView;
+    }
+
+    bool saveStateToFile() {
+        if (activeRomStatePath.empty())
+            return false;
+
+        FILE* file = std::fopen(activeRomStatePath.c_str(), "wb");
+        if (!file)
+            return false;
+
+        const size_t written = std::fwrite(&gb, 1, sizeof(gb), file);
+        std::fclose(file);
+        return written == sizeof(gb);
+    }
+
+    bool loadStateFromFile() {
+        if (activeRomStatePath.empty())
+            return false;
+
+        FILE* file = std::fopen(activeRomStatePath.c_str(), "rb");
+        if (!file)
+            return false;
+
+        std::vector<uint8_t> backup(sizeof(gb));
+        std::memcpy(backup.data(), &gb, sizeof(gb));
+
+        const size_t read = std::fread(&gb, 1, sizeof(gb), file);
+        std::fclose(file);
+        if (read != sizeof(gb)) {
+            std::memcpy(&gb, backup.data(), sizeof(gb));
+            return false;
+        }
+
+        applyRuntimeBindings();
+        gb.direct.joypad = 0xFF;
+        frameDirty       = true;
+        return true;
+    }
+
+    bool stateFileExists() const {
+        if (activeRomStatePath.empty())
+            return false;
+        struct stat st{};
+        return stat(activeRomStatePath.c_str(), &st) == 0 && S_ISREG(st.st_mode);
+    }
+
+    void enterPrompt(PromptKind kind) {
+        if (kind == PromptKind::None)
+            return;
+        promptKind       = kind;
+        promptSelection  = 0;
+        promptDirty      = true;
+        mode             = Mode::Prompt;
+        gb.direct.joypad = 0xFF;
+        scheduleNextTick(0);
+    }
+
+    void exitPrompt(Mode nextMode) {
+        promptKind      = PromptKind::None;
+        promptSelection = 0;
+        promptDirty     = true;
+        mode            = nextMode;
+    }
+
+    void handlePromptInput(const InputState& input) {
+        if (promptKind == PromptKind::None)
+            return;
+
+        const bool leftOrUp    = (input.left && !prevInput.left) || (input.up && !prevInput.up);
+        const bool rightOrDown = (input.right && !prevInput.right) || (input.down && !prevInput.down);
+        if (leftOrUp && promptSelection != 0) {
+            promptSelection = 0;
+            promptDirty     = true;
+        } else if (rightOrDown && promptSelection != 1) {
+            promptSelection = 1;
+            promptDirty     = true;
+        }
+
+        const bool confirm = (input.a && !prevInput.a) || (input.start && !prevInput.start);
+        const bool cancel  = (input.b && !prevInput.b) || (input.select && !prevInput.select);
+
+        if (confirm) {
+            handlePromptDecision(promptSelection == 0);
+        } else if (cancel) {
+            handlePromptDecision(false);
+        }
+    }
+
+    void handlePromptDecision(bool yesSelected) {
+        const PromptKind kind = promptKind;
+        if (kind == PromptKind::None)
+            return;
+
+        if (kind == PromptKind::LoadState) {
+            exitPrompt(Mode::Running);
+            if (yesSelected) {
+                if (loadStateFromFile())
+                    setStatus("Save state loaded");
+                else
+                    setStatus("Load state failed");
+            }
+            frameDirty = true;
+            return;
+        }
+
+        if (kind == PromptKind::SaveState) {
+            const bool haveStatePath = !activeRomStatePath.empty();
+            bool       saved         = false;
+            if (yesSelected && haveStatePath)
+                saved = saveStateToFile();
+
+            exitPrompt(Mode::Running);
+            unloadRom();
+
+            if (yesSelected) {
+                if (!haveStatePath)
+                    setStatus("Save state unavailable");
+                else if (saved)
+                    setStatus("Save state written");
+                else
+                    setStatus("Save state failed");
+            } else {
+                setStatus("Exited without state");
+            }
+        }
+    }
+
+    void renderPrompt() {
+        if (!promptDirty || promptKind == PromptKind::None)
+            return;
+        promptDirty = false;
+
+        framebuffer.frameReady();
+        framebuffer.clear(false);
+
+        auto drawCentered = [&](int y, std::string_view text, int scale = 1) {
+            const int width = font16x8::measureText(text, scale, 1);
+            const int x     = (framebuffer.width() - width) / 2;
+            font16x8::drawText(framebuffer, x, y, text, scale, true, 1);
+        };
+
+        std::string_view headline;
+        std::string_view helper;
+
+        switch (promptKind) {
+            case PromptKind::LoadState:
+                headline = "LOAD SAVE STATE?";
+                helper   = "A YES / B NO";
+                break;
+            case PromptKind::SaveState:
+                headline = "SAVE BEFORE EXIT?";
+                helper   = "A YES / B NO";
+                break;
+            case PromptKind::None:
+            default:
+                headline = "";
+                helper   = "";
+                break;
+        }
+
+        drawCentered(40, headline);
+        drawCentered(72, helper);
+
+        const std::string yesLabel = (promptSelection == 0) ? "> YES" : "  YES";
+        const std::string noLabel  = (promptSelection == 1) ? "> NO" : "  NO";
+
+        drawCentered(104, yesLabel);
+        drawCentered(120, noLabel);
+
+        framebuffer.sendFrame();
+    }
+
     void playTone(uint32_t freqHz, uint32_t durationMs, uint32_t gapMs) {
         if (freqHz == 0 || durationMs == 0)
             return;
@@ -1739,6 +1998,21 @@ public:
         return result;
     }
 
+    static std::string buildStatePath(const RomEntry& rom, std::string_view romDir) {
+        std::string slug = rom.saveSlug;
+        if (slug.empty())
+            slug = sanitizeSaveSlug(rom.name);
+        if (slug.empty())
+            slug = "rom";
+
+        std::string result(romDir);
+        if (!result.empty() && result.back() != '/')
+            result.push_back('/');
+        result.append(slug);
+        result.append(".state");
+        return result;
+    }
+
     static GameboyApp* fromGb(struct gb_s* gb) {
         CARDBOY_CHECK_CODE(if (!gb) return nullptr;);
         return static_cast<GameboyApp*>(gb->direct.priv);
@@ -1926,35 +2200,6 @@ private:
                 drawLineOriginal(*self, pixels, static_cast<int>(line));
                 break;
         }
-
-        // Simple per-scanline hook: at end of last line, decide tone for the frame.
-        if (line + 1 == LCD_HEIGHT) {
-            uint32_t freqHz = 0;
-            uint8_t  loud   = 0;
-            if (self->apu.computeEffectiveTone(freqHz, loud)) {
-                // Basic smoothing: if freq didn't change much, keep it; otherwise snap quickly
-                const uint32_t prev = self->lastFreqHz;
-                if (prev != 0 && freqHz != 0) {
-                    const uint32_t diff = (prev > freqHz) ? (prev - freqHz) : (freqHz - prev);
-                    if (diff < 15) {
-                        freqHz = prev; // minor jitter suppression
-                        ++self->stableFrames;
-                    } else {
-                        self->stableFrames = 0;
-                    }
-                } else {
-                    self->stableFrames = 0;
-                }
-                self->lastFreqHz     = freqHz;
-                self->lastLoud       = loud;
-                const uint32_t durMs = 17;
-                self->playTone(freqHz, durMs, 0);
-            } else {
-                self->lastFreqHz = 0;
-                self->lastLoud   = 0;
-                // Don't enqueue anything; queue naturally drains and buzzer stops
-            }
-        }
     }
 
     static const char* initErrorToString(enum gb_init_error_e err) {

Firmware/sdk/apps/snake/CMakeLists.txt

@@ -0,0 +1,9 @@
+target_sources(cardboy_apps
+        PRIVATE
+        ${CMAKE_CURRENT_SOURCE_DIR}/src/snake_app.cpp
+)
+
+target_include_directories(cardboy_apps
+        PUBLIC
+        ${CMAKE_CURRENT_SOURCE_DIR}/include
+)

Firmware/sdk/apps/snake/include/cardboy/apps/snake_app.hpp

@@ -0,0 +1,11 @@
+#pragma once
+
+#include "cardboy/sdk/app_framework.hpp"
+
+#include <memory>
+
+namespace apps {
+
+std::unique_ptr<cardboy::sdk::IAppFactory> createSnakeAppFactory();
+
+} // namespace apps

Firmware/sdk/apps/snake/src/snake_app.cpp

@@ -0,0 +1,432 @@
+#include "cardboy/apps/snake_app.hpp"
+
+#include "cardboy/apps/menu_app.hpp"
+#include "cardboy/gfx/font16x8.hpp"
+#include "cardboy/sdk/app_framework.hpp"
+#include "cardboy/sdk/app_system.hpp"
+#include "cardboy/sdk/display_spec.hpp"
+#include "cardboy/sdk/input_state.hpp"
+
+#include <algorithm>
+#include <cstdint>
+#include <cstdlib>
+#include <deque>
+#include <random>
+#include <string>
+#include <string_view>
+#include <vector>
+
+namespace apps {
+namespace {
+
+using cardboy::sdk::AppButtonEvent;
+using cardboy::sdk::AppContext;
+using cardboy::sdk::AppEvent;
+using cardboy::sdk::AppEventType;
+using cardboy::sdk::AppTimerHandle;
+using cardboy::sdk::InputState;
+
+constexpr char kSnakeAppName[] = "Snake";
+
+constexpr int kBoardWidth           = 32;
+constexpr int kBoardHeight          = 20;
+constexpr int kCellSize             = 10;
+constexpr int kInitialSnakeLength   = 5;
+constexpr int kScorePerFood         = 10;
+constexpr int kMinMoveIntervalMs    = 80;
+constexpr int kBaseMoveIntervalMs   = 220;
+constexpr int kIntervalSpeedupPerSegment = 4;
+
+struct Point {
+    int x = 0;
+    int y = 0;
+
+    bool operator==(const Point& other) const { return x == other.x && y == other.y; }
+};
+
+enum class Direction { Up, Down, Left, Right };
+
+[[nodiscard]] std::uint32_t randomSeed(AppContext& ctx) {
+    if (auto* rnd = ctx.random())
+        return rnd->nextUint32();
+    static std::random_device rd;
+    return rd();
+}
+
+class SnakeGame {
+public:
+    explicit SnakeGame(AppContext& ctx) : context(ctx), framebuffer(ctx.framebuffer) {
+        rng.seed(randomSeed(context));
+        loadHighScore();
+        reset();
+    }
+
+    void onStart() {
+        scheduleMoveTimer();
+        dirty = true;
+        renderIfNeeded();
+    }
+
+    void onStop() { cancelMoveTimer(); }
+
+    void handleEvent(const AppEvent& event) {
+        switch (event.type) {
+            case AppEventType::Button:
+                handleButtons(event.button);
+                break;
+            case AppEventType::Timer:
+                handleTimer(event.timer.handle);
+                break;
+        }
+        renderIfNeeded();
+    }
+
+private:
+    AppContext&                       context;
+    typename AppContext::Framebuffer& framebuffer;
+
+    std::deque<Point> snake;
+    Point             food{};
+    Direction         direction       = Direction::Right;
+    Direction         queuedDirection = Direction::Right;
+    bool              paused          = false;
+    bool              gameOver        = false;
+    bool              dirty           = false;
+    int               score           = 0;
+    int               highScore       = 0;
+    AppTimerHandle moveTimer = cardboy::sdk::kInvalidAppTimer;
+    std::mt19937   rng;
+
+    void handleButtons(const AppButtonEvent& evt) {
+        const auto& cur  = evt.current;
+        const auto& prev = evt.previous;
+        if (cur.b && !prev.b) {
+            context.requestAppSwitchByName(kMenuAppName);
+            return;
+        }
+
+        if (cur.select && !prev.select) {
+            reset();
+            return;
+        }
+
+        if (cur.start && !prev.start) {
+            if (gameOver)
+                reset();
+            else {
+                paused = !paused;
+                dirty  = true;
+            }
+        }
+
+        if (gameOver)
+            return;
+
+        if (cur.up && !prev.up)
+            queueDirection(Direction::Up);
+        else if (cur.down && !prev.down)
+            queueDirection(Direction::Down);
+        else if (cur.left && !prev.left)
+            queueDirection(Direction::Left);
+        else if (cur.right && !prev.right)
+            queueDirection(Direction::Right);
+
+        if (cur.a && !prev.a && !paused)
+            advance();
+    }
+
+    void handleTimer(AppTimerHandle handle) {
+        if (handle == moveTimer && !paused && !gameOver)
+            advance();
+    }
+
+    void reset() {
+        cancelMoveTimer();
+
+        snake.clear();
+        const int centerX = kBoardWidth / 2;
+        const int centerY = kBoardHeight / 2;
+        for (int i = 0; i < kInitialSnakeLength; ++i)
+            snake.push_back(Point{centerX - i, centerY});
+
+        direction       = Direction::Right;
+        queuedDirection = Direction::Right;
+        paused          = false;
+        gameOver        = false;
+        score           = 0;
+        dirty           = true;
+
+        if (!spawnFood())
+            onGameOver();
+
+        scheduleMoveTimer();
+    }
+
+    void advance() {
+        direction = queuedDirection;
+        Point nextHead = snake.front();
+        switch (direction) {
+            case Direction::Up:
+                --nextHead.y;
+                break;
+            case Direction::Down:
+                ++nextHead.y;
+                break;
+            case Direction::Left:
+                --nextHead.x;
+                break;
+            case Direction::Right:
+                ++nextHead.x;
+                break;
+        }
+
+        if (isCollision(nextHead)) {
+            onGameOver();
+            return;
+        }
+
+        snake.push_front(nextHead);
+        if (nextHead == food) {
+            score += kScorePerFood;
+            updateHighScore();
+            if (!spawnFood()) {
+                onGameOver();
+                return;
+            }
+            scheduleMoveTimer();
+            if (auto* buzzer = context.buzzer())
+                buzzer->beepMove();
+        } else {
+            snake.pop_back();
+        }
+
+        dirty = true;
+    }
+
+    [[nodiscard]] bool isCollision(const Point& nextHead) const {
+        if (nextHead.x < 0 || nextHead.x >= kBoardWidth || nextHead.y < 0 || nextHead.y >= kBoardHeight)
+            return true;
+        return std::find(snake.begin(), snake.end(), nextHead) != snake.end();
+    }
+
+    void onGameOver() {
+        if (gameOver)
+            return;
+        gameOver = true;
+        cancelMoveTimer();
+        dirty = true;
+        if (auto* buzzer = context.buzzer())
+            buzzer->beepGameOver();
+    }
+
+    void queueDirection(Direction next) {
+        if (isOpposite(direction, next) || isOpposite(queuedDirection, next))
+            return;
+        queuedDirection = next;
+    }
+
+    [[nodiscard]] static bool isOpposite(Direction a, Direction b) {
+        if ((a == Direction::Up && b == Direction::Down) || (a == Direction::Down && b == Direction::Up))
+            return true;
+        if ((a == Direction::Left && b == Direction::Right) || (a == Direction::Right && b == Direction::Left))
+            return true;
+        return false;
+    }
+
+    bool spawnFood() {
+        std::vector<Point> freeCells;
+        freeCells.reserve(kBoardWidth * kBoardHeight - static_cast<int>(snake.size()));
+        for (int y = 0; y < kBoardHeight; ++y) {
+            for (int x = 0; x < kBoardWidth; ++x) {
+                Point p{x, y};
+                if (std::find(snake.begin(), snake.end(), p) == snake.end())
+                    freeCells.push_back(p);
+            }
+        }
+        if (freeCells.empty())
+            return false;
+        std::uniform_int_distribution<std::size_t> dist(0, freeCells.size() - 1);
+        food = freeCells[dist(rng)];
+        return true;
+    }
+
+    void scheduleMoveTimer() {
+        cancelMoveTimer();
+        const std::uint32_t interval = currentInterval();
+        moveTimer  = context.scheduleRepeatingTimer(interval);
+    }
+
+    void cancelMoveTimer() {
+        if (moveTimer != cardboy::sdk::kInvalidAppTimer) {
+            context.cancelTimer(moveTimer);
+            moveTimer = cardboy::sdk::kInvalidAppTimer;
+        }
+    }
+
+    [[nodiscard]] std::uint32_t currentInterval() const {
+        int interval = kBaseMoveIntervalMs - static_cast<int>(snake.size()) * kIntervalSpeedupPerSegment;
+        if (interval < kMinMoveIntervalMs)
+            interval = kMinMoveIntervalMs;
+        return static_cast<std::uint32_t>(interval);
+    }
+
+    void updateHighScore() {
+        if (score <= highScore)
+            return;
+        highScore = score;
+        if (auto* storage = context.storage())
+            storage->writeUint32("snake", "best", static_cast<std::uint32_t>(highScore));
+    }
+
+    void loadHighScore() {
+        if (auto* storage = context.storage()) {
+            std::uint32_t stored = 0;
+            if (storage->readUint32("snake", "best", stored))
+                highScore = static_cast<int>(stored);
+        }
+    }
+
+    void renderIfNeeded() {
+        if (!dirty)
+            return;
+        dirty = false;
+
+        framebuffer.frameReady();
+        framebuffer.clear(false);
+
+        drawBoard();
+        drawFood();
+        drawSnake();
+        drawHud();
+
+        framebuffer.sendFrame();
+    }
+
+    [[nodiscard]] int boardOriginX() const {
+        return (cardboy::sdk::kDisplayWidth - kBoardWidth * kCellSize) / 2;
+    }
+
+    [[nodiscard]] int boardOriginY() const {
+        const int centered = (cardboy::sdk::kDisplayHeight - kBoardHeight * kCellSize) / 2;
+        return std::max(24, centered);
+    }
+
+    void drawBoard() {
+        const int originX = boardOriginX();
+        const int originY = boardOriginY();
+        const int width   = kBoardWidth * kCellSize;
+        const int height  = kBoardHeight * kCellSize;
+
+        const int x0 = originX;
+        const int y0 = originY;
+        const int x1 = originX + width - 1;
+        const int y1 = originY + height - 1;
+        for (int x = x0; x <= x1; ++x) {
+            framebuffer.drawPixel(x, y0, true);
+            framebuffer.drawPixel(x, y1, true);
+        }
+        for (int y = y0; y <= y1; ++y) {
+            framebuffer.drawPixel(x0, y, true);
+            framebuffer.drawPixel(x1, y, true);
+        }
+    }
+
+    void drawSnake() {
+        if (snake.empty())
+            return;
+        std::size_t index = 0;
+        for (const auto& segment: snake) {
+            drawSnakeSegment(segment, index == 0);
+            ++index;
+        }
+    }
+
+    void drawSnakeSegment(const Point& segment, bool head) {
+        const int originX = boardOriginX() + segment.x * kCellSize;
+        const int originY = boardOriginY() + segment.y * kCellSize;
+        for (int dy = 0; dy < kCellSize; ++dy) {
+            for (int dx = 0; dx < kCellSize; ++dx) {
+                const bool border = dx == 0 || dy == 0 || dx == kCellSize - 1 || dy == kCellSize - 1;
+                bool       fill   = ((dx + dy) & 0x1) == 0;
+                if (head)
+                    fill = true;
+                const bool on = border || fill;
+                framebuffer.drawPixel(originX + dx, originY + dy, on);
+            }
+        }
+    }
+
+    void drawFood() {
+        const int cx = boardOriginX() + food.x * kCellSize + kCellSize / 2;
+        const int cy = boardOriginY() + food.y * kCellSize + kCellSize / 2;
+        const int r  = std::max(2, kCellSize / 2 - 1);
+        for (int dy = -r; dy <= r; ++dy) {
+            for (int dx = -r; dx <= r; ++dx) {
+                if (std::abs(dx) + std::abs(dy) <= r)
+                    framebuffer.drawPixel(cx + dx, cy + dy, true);
+            }
+        }
+    }
+
+    void drawHud() {
+        const int         margin   = 12;
+        const int         textY    = 8;
+        const std::string scoreStr = "SCORE " + std::to_string(score);
+        const std::string bestStr  = "BEST " + std::to_string(highScore);
+        font16x8::drawText(framebuffer, margin, textY, scoreStr, 1, true, 1);
+        const int bestX = cardboy::sdk::kDisplayWidth - font16x8::measureText(bestStr, 1, 1) - margin;
+        font16x8::drawText(framebuffer, bestX, textY, bestStr, 1, true, 1);
+
+        const int         footerY   = cardboy::sdk::kDisplayHeight - 24;
+        const std::string menuStr   = "B MENU";
+        const std::string selectStr = "SELECT RESET";
+        const std::string startStr  = "START PAUSE";
+        const int         selectX   = (cardboy::sdk::kDisplayWidth - font16x8::measureText(selectStr, 1, 1)) / 2;
+        const int         startX    = cardboy::sdk::kDisplayWidth - font16x8::measureText(startStr, 1, 1) - margin;
+        font16x8::drawText(framebuffer, margin, footerY, menuStr, 1, true, 1);
+        font16x8::drawText(framebuffer, selectX, footerY, selectStr, 1, true, 1);
+        font16x8::drawText(framebuffer, startX, footerY, startStr, 1, true, 1);
+
+        if (paused && !gameOver)
+            drawBanner("PAUSED");
+        else if (gameOver)
+            drawBanner("GAME OVER");
+    }
+
+    void drawBanner(std::string_view text) {
+        const int w = font16x8::measureText(text, 2, 1);
+        const int h = font16x8::kGlyphHeight * 2;
+        const int x = (cardboy::sdk::kDisplayWidth - w) / 2;
+        const int y = boardOriginY() + kBoardHeight * kCellSize / 2 - h / 2;
+        for (int yy = -4; yy < h + 4; ++yy)
+            for (int xx = -6; xx < w + 6; ++xx)
+                framebuffer.drawPixel(x + xx, y + yy, yy == -4 || yy == h + 3 || xx == -6 || xx == w + 5);
+        font16x8::drawText(framebuffer, x, y, text, 2, true, 1);
+    }
+};
+
+class SnakeApp final : public cardboy::sdk::IApp {
+public:
+    explicit SnakeApp(AppContext& ctx) : game(ctx) {}
+
+    void onStart() override { game.onStart(); }
+    void onStop() override { game.onStop(); }
+    void handleEvent(const AppEvent& event) override { game.handleEvent(event); }
+
+private:
+    SnakeGame game;
+};
+
+class SnakeFactory final : public cardboy::sdk::IAppFactory {
+public:
+    const char*                         name() const override { return kSnakeAppName; }
+    std::unique_ptr<cardboy::sdk::IApp> create(AppContext& context) override {
+        return std::make_unique<SnakeApp>(context);
+    }
+};
+
+} // namespace
+
+std::unique_ptr<cardboy::sdk::IAppFactory> createSnakeAppFactory() { return std::make_unique<SnakeFactory>(); }
+
+} // namespace apps

Firmware/sdk/launchers/desktop/src/main.cpp

@@ -2,6 +2,7 @@
 #include "cardboy/apps/gameboy_app.hpp"
 #include "cardboy/apps/menu_app.hpp"
 #include "cardboy/apps/settings_app.hpp"
+#include "cardboy/apps/snake_app.hpp"
 #include "cardboy/apps/tetris_app.hpp"
 #include "cardboy/backend/desktop_backend.hpp"
 #include "cardboy/sdk/app_system.hpp"
@@ -29,6 +30,7 @@ int main() {
         system.registerApp(apps::createSettingsAppFactory());
         system.registerApp(apps::createClockAppFactory());
         system.registerApp(apps::createGameboyAppFactory());
+        system.registerApp(apps::createSnakeAppFactory());
         system.registerApp(apps::createTetrisAppFactory());
 
         system.run();