The idea of a crumbling floor in a topdown shooter that gets more hectic is a really interesting idea.
The biggest things hindering this game are: - Picking up powerups requires you to stop, during the middle of the crumbling floor, oncoming enemies, and your sizeable acceleration that makes you immediately run past the powerups. Powerups also spawn at a very fast rate, you'd probably be better off making them rarer and not having to press a key to equip them. - The audio is extremely repetitive and becomes downright annoying, and also a little loud when it comes to the gunshot. A little change or two in each, as well as a little volume decrease wouldn't hurt.
- Enemies don't pose much of a threat, they're pretty slow and only fire a few bullets on a huge floor
- The spaces between the towers seem a little unnecessary, the gaps are huge, and you're fighting the same types of enemies over and over, so the spacing seems kinda pointless when you could just defend one tower and take the risk of going out for powerups further out on a map.