Holy hell this is a cool entry !
I really like the instant action as soon as you choose your room, the concept of having it shring any time you take a hit is very unique and is a nice take on the theme.
The spritework even though they are tiny have got some character to them cause of how they're animated, bullet patterns do get quite tough but feel managable.
And the tradeoff upgrade system is a nice idea though it does make for some very tough choices.
The music is an absolute ultra banger \m/ è_é
To sum things up i'd say solid overall, quite a bit of polish and juicy feedback for a jam game.
Congrats ! Especially for a solo effort, you did great :D