It's been a little while! I really enjoyed doing the compo a couple of years ago - sound design gets a lot more interesting when you can't rely on your libraries. I've had a couple of thoughts for what I might do this time:
1) Groundhog Day
I'm fairly sure this is what sprung to mind for most people when they first saw the theme. You have a limited amount of time in the game before everything resets, at which point all you can bring forward is the knowledge you've gained in previous rounds. Perhaps you're trapped in an abandoned mansion, and on one round, you solve a puzzle that gives you the code to a safe, so that in the next round, you can open it, retrieve the key that's inside, and escape the room you're in. (Ooh, an escape room, there's a thought.)
2) Bungee Cord
Instead of having the entire game state revert, only the player position is reset after the time limit. Imagine a maze in which you only have 30 seconds to get to the exit, which isn't enough because it's a long and winding path. Now, imagine that you can take a secondary route in your first round to push an obstacle out of the way, opening up a shorter route to the goal.
3) Derailed
You're on an out-of-control train. Thankfully, there are no cliff edges anywhere in sight, and the track is in a loop. You need to lean out and press switches in order to change the junctions so that the train takes a different path.
I'm leaning more towards 1 or 2. I really enjoyed the 3D work and horror aesthetic I did last time, so if I can lean into that, I will.