Crushing ceilings appear in Doom, Heretic, Hexen, and Strife. A crushing ceiling cycles between its starting height and eight units above its sector's floor. It damages any player or monster that happens to be in between. In Doom, barrels explode when crushed, corpses become pools of blood, and weapons and clips dropped by zombies disappear. (Ghost monsters and their corpses are unaffected.) Crushing ceilings also destroy projectiles, whether fired by the player or by monsters. Due to a bug, barrels also leave pools of blood when crushed .