I don't even know

example.c

struct crb_game {
    int      state;
    char    *name;

    crb_gfx *gfx;
    crb_snd *snd;
    crb_lua *lua;

    int (*on_start)(void);
    int (*on_stop)(void);
};

struct shootemup_game {
    struct crb_game  base;

    struct player   *player;

    unsigned         level;
    unsigned         score;
};