By closing the doors (the ones which lead from room to room) you can lock out the effects. Try to lock out the effect which makes the tentacles appear from the first room (didn't have the time for a proper tutorial, the itch page gives a bit of info on the mechanics)
OH MY, ok, you need to close ALL THE DOORS leading to the room you want the effect to stop, not only the adjacent one! I was closing the door at the left of the "tentacle room", thinking that would be enough, but the effect was going all the way down/left/up so I had to also lock that one ^^. That makes sense now that I nkow about it, but a little visual effect coming from the doors would probably have helped me understand ^^.
Now my understanding of your concept is waaaaaay better, and your game makes a lot more sense (and fits in the theme more than what I thought)! I'll try to reach the end and adjust my ratings accordingly, thank you for your help ;)