This was A really fun game! Variety in enemies and the fact that the powerups made the next level feel harder was a great idea, I would buy everything though every round and at one point I couldn't buy anymore due to not being able to go over 5x speed, that was a bit of a bummer, I wish that it would have let me choose like hardcore mode and the enemies would have started to make like 2x the damage, but I could buy as much as I wanted :D
I think the game bugged out two times. First time I went through the classic mode, beat the boss and then it started coming with normal levels again for few rounds before it through me back to start (I couldn't read what it said since it went so fast) Then I went to play the boss mode (again the 5x speed limit bummed me out a bit :/ ) and after multiple bosses I was left alone jumping in the level, with no way out and no enemies or anything anymore, had to ALT + F4 out from the game :D
Overall amazing game even though it was so simply made.