"So the puzzles are driven by a handheld device called a Portal G... Oh, wait. Actually a sort of power glove thing that allows you to shift between four alternate dimensions (read screen filters) that alter the physical properties of the objects around you. It's kind of like a glove-mounted cocktail dispenser, except that it alters the physical properties of things other than your own legs. There's the Piña Colada dimension where everything is light and fruity; the Black Russian dimension where things sit much more heavily and you start clutching your head complaining about your ex-wife; the Absinthe dimension where everything floats off into the sky to come crashing apocalyptically down the following morning; and the slow-motion dimension where this analogy kind of breaks down."