So heres my idea: When you acquire a hoverbike, there is a random chance of a floating ship in the planet you are in (location is random, but it is located high). There is a bar with a shopkeeper that sells health drinks, and a gang of bikers with different models of hoverbikes (on each type of planet there would be a different model of bike). When you talk to them they challenge you to a race around the planet. If you win you get 10% discounts at the shop in the ship, and you get the model of hoverbike that matches the planet you done the race in. If you lose, you pay them money but the next race will be easier. As you beat the races, obstacles will start to spawn in the sky. They push you back when you hit them, and disappear when you pass them or when the race ends. (Note that to start the race there has to be enough space in the sky)Upon winning every type of hoverbike you unlock the 3d wormhole race. The race has great rewards such as big money, and the ability to drop mines from your hoverbike when you fly it.