the graphics and animations are very very cool, and the fact that this was made with pygame makes it 10x more cooler. well done! if I could give just a couple of criticisms that aren't even that major, I would say:
- there should be a fullscreen option (I assume you're using the pygame.SCALED flag)
- the SFX for clicking is too loud
- the animation when you die is really slow/only has a couple of frames
-clicking X in the top right corner does nothing when paused, and maybe in other scenarios too idk
- you should be able to return to the main menu when you pause the game
- it's easy to accidentally click outside of the game then die because of it
overall, super solid stuff! well done, I really like its concept/gameplay/upgrade system!