My son has disney infinity marvel for his xbox 360. We bought a couple of power up discs today. Nothing happens when we put the hexagonal disc on. Is there something else we have to do? Have managed to work out that we put the round power up under a character. They don't come with any instructions and I try to stay away from the xbox. Would be interested if anyone has had any success with these. At least they don't cost that much. Thanks.