Interesting idea.
Could do with a bit more balancing. It looks like there's a whole big dungeon, but doing the puzzles and returning back to the hourglass takes too long, so I can only clear the 3 immediately-adjacent rooms before the timer runs out. A simple alternative would be to just have the hourglass on the UI and picking up a blue thing pauses it immediately.
I agree about the reloading: an cool idea, but maybe not quite the correct game for that.
I also can't figure out how to leave the dungeon. I'd think the escape is by the door that closes when the timer runs out, but I tried pressing every key while standing there, and also standing there when the time ran out, and nothing worked. If the escape is somewhere else and you need to find it, that's probably what should close instead, when the timer runs out.