I paid for the upgrades on this game but I have gotten to where I can't play it any more because it's just non-stop grinding. You get more coins for upgrades if you die halfway through the level than if you actually beat the levels. The entire game is rigged to try to force you to pay $0.99 for 5000 coins at a time. Upgrades take progressively more coins and then have a cooldown timer on top of that, too, which you can skip with, you guessed it, more coins. Fun gameplay ruined by pay-to-win.