Alongside the traditional platform elements such as jumping on enemies heads, spikes and moving platforms are the gateway guns. The gateway guns allow you to place two gateways on the walls, floors and ceilings of the lab so that when you pass through one you emerge out of the other. As progress is made through the game different types of gateway gun are introduced with different effects. After the basic gun, you acquire a gun that creates two gateways of different sizes, passing through one way shrinks Ed to half his size and the other way makes Ed grow to twice his size. Then you find a gun where one gateway doesn\'t just connect to the others location but also its time, allowing Ed to travel back in time and encounter earlier versions of himself. Finally, the last gun manipulates gravity so passing through allows Ed to walk along walls and on ceilings.