Rising, it climbs one unit a frame with a sound whose pitch follows its height, until it is more than 31 above the floor. Falling, it gets an extra unit of downward speed each frame on top of gravity, so it falls with twice the pull of anything else, and lands with a crash of noise. While it moves it has bit 7 of +$0D set, which passes the deadly mark (bit 6) to whatever it moves into: a falling portcullis kills. It stays still while the player is settling into the room.