I love how creative this is! I managed to get through the entire game, though you certainly gave my brain a good wrangling!
The presentation was great, gameplay was solid, levels were well thought out, and overall was an awesome concept.
My biggest criticism is definitely the lack of music and SFX. Even stock sound effects would've been enough (for future reference, you can get 100% free sounds from freesound.org), though music is understandably a harder one to source, though even some ambience would've brought this to life.
I get part of the challenge is remembering which side your key and plunger is on, though maybe some kind of indicator that isn't in your face would've been helpful.
Awesome work my guy!