When robots collide they are destroyed and form a scrap heap. Robots are also destroyed when they move into a scrap heap. The player can move a scrap heap by being adjacent to one and moving in the direction of the scrap heap, but only if there is nothing on the other side of the scrap heap in the direction of movement. Scrap heaps may not be moved off of the playing field. Antimatter has no effect on a scrap heap.