Although the game is excellent how it is now, there is a multitude of ways it can be improved. For one, there should be graphics showing different levels of currency when dropped from enemies. These could be singular coins (x1), coin stacks (x10), coin piles (x50), coin bags (x100) coin chests (x1000+). Also, there needs to be a save data for all of the levels. It is annoying when you're at 9/10 progress, and you want to grind at a previous boss level for the one next, and then it depletes back to 0/10 progress. There should be an upgrade system for power ups too, not to make them stronger or anything like that, but to consume less time and maybe extend the time limit a bit.
So overall, this game gets 4 stars out of 5.