diff --git a/du8/game.h b/du8/game.h
new file mode 100644
index 0000000..0c4e07b
--- /dev/null
+++ b/du8/game.h
@@ -0,0 +1,19 @@
+#ifndef GAME_H
+#define GAME_H
+
+typedef enum { EMPTY = '.', PLAYER_X = 'X', PLAYER_O = 'O' } Cell;
+
+typedef struct {
+    Cell board[3][3];
+    int current_player;
+    int game_over;
+    int winner;
+} GameState;
+
+void init_game(GameState* game);
+void draw_game(GameState* game);
+void handle_input(GameState* game, int key);
+int check_winner(GameState* game);
+
+#endif
+