Ok so the game is good, but needs a lot more polish:
In the graphical side: The game felt empty, the assets pixel ratio don't match so it feels asset swapped, ex: The ground compared to the player, but the UI was rly cool, the camera was really zoomed out on a small character, this also can be a mechanical flaw.
In the mechanics side: The game was not well balanced, in wave 1 I got a lot of enemies at once, to improve this, maybe instead of quantity, you might increase their damage, or more complex AI (but that will take more time), the upgrades were a bit also unbalanced based on how many enemies spawn each wave.
In audio: There sadly weren't any audio, but this game could had cool music each wave!
For the theme: I think it fits it quite well.
Overall, this game was pretty cool, I rly wanna see you improve on it