Mario Kart 8 introduced a "zero gravity" feature where, in certain parts of tracks could be driven on upside down and sideways. This addition to the series is interesting though, as it isn't explained how this would function. The carts levitate above the track while in "zero gravity" mode, yet don't fall away from the stage. Also, while in this mode, you still have the ability to accelerate and decelerate. This should be impossible without some kind of force coming from the cart. Sure, there are some kind of thrusters, but these only visibly activate after using a speed item. Additionally, tracks at an angle to the force of gravity would have carts moving towards the force of gravity.