Add cursed apple: a status-effect apple that inverts controls

Eating a cursed apple inverts the snake's steering for
CURSE_DURATION_TICKS ticks, shown on the top screen while active. The
sprite is a recolored copy of the rotten-apple tile since all existing
sprite tiles are already in use.

include/consts.h

@@ -5,6 +5,7 @@
 const int START_LENGTH = 4;
 const int START_LENGTH_HARD =2;
 const int APPLE_SCORE = 10;
+const int CURSE_DURATION_TICKS = 40;
 
 //Screen size
 const int X_MAX = 31;

include/game_logic.h

@@ -7,7 +7,10 @@ void update_snake(GameState &state);
 bool check_collision_self(GameState &state);
 bool check_collision_apples(GameState &state);
 bool check_collision_apples_rotten(GameState &state);
+bool check_collision_apples_cursed(GameState &state);
 void spawn_apples(GameState &state);
 void spawn_apples_rotten(GameState &state);
+void spawn_apples_cursed(GameState &state);
+void tick_status_effects(GameState &state);
 
 #endif

include/game_render.h

@@ -15,6 +15,7 @@ struct RenderAssets {
     u16 *gfx_apple = nullptr;
     u16 *gfx_tail = nullptr;
     u16 *gfx_apple_rotten = nullptr;
+    u16 *gfx_apple_cursed = nullptr;
 };
 
 void draw_game(const GameState &state, const RenderAssets &assets);

include/game_state.h

@@ -16,9 +16,12 @@ struct GameState {
     bool paused = false;
     bool hardMode = false;
 
+    uint16_t curseTicksRemaining = 0;
+
     std::deque<std::array<int, 3>> snake;
     std::vector<std::array<int, 2>> apples;
     std::vector<std::array<int, 2>> bad_apples;
+    std::vector<std::array<int, 2>> cursed_apples;
 };
 
 #endif