I managed to give this game a try after finding it on my itchi.io dashboard and I've been experimenting with as much as I could. There are quite a lot of potential aspects with these sorts of puzzles such as finding pieces to create or unlock a door, or maybe having obstacles that only appear to eat at your limited time such as tentacles that make them creep up faster.
One of my major suggestions if there won't be any hud elements is a bit of a simpler tell that time is starting to tick down. The first time I saw the tentacles I was spooked by them given how sudden they appeared, but after getting used to it I realized the lack of tells can be a little difficult
I think the smoke / haze that begins to creepy up from the edges would be a much more subtle tell that could lead to it getting thicker and tentacles appearing from it. This is just a small suggestion though.