It's a nice concept, but I got stuck on the level up screen :(
Viewing post in Slime Chain Effect jam comments
It might be because of the mouse. I know options can go out of focus because of that. You can point/click with your mouse to focus again on the power up you want. Then press spacebar to confirm your choice. Normally, you should be able to select the power ups with just arrow keys and space bar. Hope this solves you issue! :)