Super Mario Galaxy is impossible. Don't get the wrong idea – it's not a particularly difficult game, although it does have its moments. What Edge means is, it obeys no rules, contradicts everything gamers know, and has no right to exist.
Mario Galaxy turns 3D into 2D, and 2D into 3D. It takes complex spatial ideas and makes them simple and instinctive; it takes the most basic, most familiar acts in gaming and makes them strange, finger-twisting and fresh. It resurrects the pure platform game in a universe where it's hard to fall off things. It rewrites its own rules in almost every level, sometimes more than once. Super Mario Galaxy rejoices in turning the world upside down.