Great game! I've been hooked!!
I will say that the prestige mechanic/tree definitely needs rebalancing -- as you continue to prestige, early level completion requirements go up at a scale that makes it so that the more you prestige -> fewer levels you can complete, so it quickly becomes pretty painful to try and earn enough prestige points to upgrade anything in the prestige tree, which in turn makes prestige less worthwhile because level completion requirements go up at a constant rate w/prestige yet there's very little increase in what you actually earn.