In games where the player can ride Yoshi, he acts as an extra hit point; taking damage causes the player to be knocked off Yoshi instead of any other negative effects. This makes Yoshi start to run around haphazardly until he is remounted or falls off-screen. Yoshi is otherwise indestructible; he can freely walk over spikes, does more damage to enemies when jumped on, and can take any number of hits without additional penalty. Combined with his other unique powers, this makes him very strong in levels designed for Mario's abilities, while a level designed for Yoshi may be overly difficult for Mario alone. As a result, Yoshi's presence tends to be limited to certain levels; for example, in "Super Mario World" he is not allowed in haunted or castle levels (explained in-universe by him being scared of such areas). While riding Yoshi, bongos or other thematically-appropriate percussion instruments are added to the level's background music.