This is a genuinely cool game.
One thing I really liked about the game was the genuine difficulty scale, I genuinely had to think hard about which mouse to place and where in order to complete each new level. (Not sure if there is an end to the game since I didn't reach it)
Some things I think you can improve on are the UI interface, and the overall gameplay "juice"
UI: I think you should work on making a custom UI menu. Something that makes your game stand out among other indie games. Since your game is based around Rat's, you could make the UI based around cheese like a cheese wheel which gets a slice taken out when you can't afford an upgrade. This would add some more personality to your already lively game
Juice: Things like Animations, particles, VFX, lighting, etc would go a long way to making your game feel more complete.
Little things like a leaf particle explosion or a gelatin particle explosion on enemy death would make the game feel more alive.
Overall great submission! Hopefully you can use this advice to make an even better game next Jam!