It's a bit rough around the edges but there are a lot of small changes you could make to really elevate the quality of this game. Try making a lighter colored floor so the character and enemies stand out better, and add a tile texture to it so it doesn't feel like everything is just floating around in space and you get a better sense of motion when you're moving around. Maybe add a spawn animation to the enemies, too.
I had fun though, and made it to the 12th wave