The Crusher was the first NPC successfully created. It was introduced into the Industrial version. Gray said, "If we made NPCs pursue the player, that wouldn't work so well on paper. If I made a computer game, it would. Darn!" Therefore, the Crushers do not pursue the player. Normal Crushers can be destroyed by explosions, Acid, or the Command Card.
The Crusher will keep traveling in a direction indicated by the arrows on its back until it hits a block or wall, at which point it will turn around. It will turn all floor tiles it touches into Void Floor Tiles. This is often used for quickly paced levels, such as Industrial Pack Level 1: Outrace the Crushers.
These Crushers perform the same action as the other Crushers, but have a catch: they can only be destroyed by the Command Card.