Mario and his pals have been tooling around the Mushroom Kingdom in go-karts for years, and yet the fun never gets old. But for “Mario Kart 8,” Nintendo is turning the whole thing upside down —literally. Within the game, driving over blue pads scattered across the track tells gravity to kiss off, allowing your character to drive up walls and ceilings. These same pads open up new shortcuts and drivable terrains. Plus, “Mario Kart 8” features a new hover kart feature that activates at specific points during races.