In my opinion, the game ends far too early. What I think you should do, is make it so there is no level cap, and an exponential equation ramps the cost of upgrades so you could go on forever while still getting more difficult. This would let you go further out infinitely. Obviously movement speed and flight would need a cap, but other things like damage hp regen etc would be good. I truly think this would let the game be much more than what it currently is, and would let people flex their levels on their character. Here is an example equation: cost = 50*(1.2)^(level). In order to fulfill high costs for upgrades, you could add an upgrade or item that increases the amount of juice you get per sphere.