The background and game style remind me a lot of that mario paint swatter minigame, in a good way! Was that an inspiration by any means?
Pretty cool arcade game, the color usage is great and the gameplay feels smooth. It does get easier over time, and at some point I knew I could go forever, which is totally fine, but I felt like I had little to no danger because there were so many mice. And as others mentioned, auto-attacking would be great as well.
I had fun though, got myself half a million point before I stopped playing. Good job!
You can check out my playthrough here if you'd like to (sometimes the video freezes for a second or so but it's just me clicking outside the window like a dummy haha):