Neat concept, I played for quite a while before I found it too hard to find more stuff. I got the 2nd mask, a speed upgrade or two, and a few others. The core idea is really cool and I can imagine it being expanded on in a tonne of ways. E.g. having some landmarks would help navigation a lot. The biggest issue I guess is it only feels like time + speed upgrades are impactful. Stamina didn't seem to do anything, and vision didn't help much more.
I'm sure you had plenty of ideas there that didn't make it in... but overall it's a really solid idea that I haven't seen before (at least not as the core mechanic). It was fun to play and has a lot of potential IMO!