I love the idea, but here are some issues:
The key to stop building/recording (ESC) is closing the fullscreen. Just have R/B also deactivate the build/record.
Unless you want to have this game be very stressful, consider having the recording done while the game timer isn't running. It felt very annoying to have an attack wave start during a record, which either forces you to break your recording or risk your buildings getting destroyed.
Also the game slows down quite a lot when you have many mice doing their thing.
After a while the game devolves into "Place a tower, use record to spam click it" repeat it a lot. (Same for "place forest, record spam click on it") I'm not sure this was intended as it is.