In Battle Mode, hold the gas before, during, and after you lose your last balloon. Sometimes you will be able to continue driving around collecting blocks. Make sure you keep holding the gas! If you inadvertently press a button, you will get the menu, but you'll still be able to drive around until you press another button. If you get a Star, use it; after the star music stops, the regular battle music returns. If you get a Red Shell, fire it at your opponent, and it'll spin circles around him.