First ever sub-21, I don't have an estimate for how low the time can go because you seem to lose and save time randomly in this game. The framerate is not consistent, so that might have something to do with it. Anyways, here are my comments on the run:

The beginning of the run was pretty normal, I grabbed the coin after the key at 13.500 seconds. I have a run that grabbed the key at 13.367 seconds, however I don't know if that was a result of better gameplay or luck. This was slower than my previous PB. Normally if you do the elevator jump, you can't get fast fall. However you can set up a fast fall by jumping after getting the coin to the right of the elevator. This jump is frame perfect, and since the game is weird it's extremely inconsistent too. Some times you get stuck in the floor and move slower, and then get fast fall. However, the fastest and unfortunately least consistent way to get fast fall is to bonk on the stairs for a bit, which loses a bit of time but then saves time over the other fast fall by not needing to slow down. If you use the "classic" route then you can get fast fall without needing to slow down at all, but that doesn't work with elevator jump route. Normally you only bonk on the stairs for 3 frames for an optimal fast fall, however I bonked for 5 frames in this run. This combined with a slow start means I should not have gotten a PB, but you save and lose time randomly, and I'm not complaining. This took over 500 attempts to get, and "perfect" fast fall had ~1/20 consistency. This was not super fun to grind. It was getting to be very tedious around the time that I finally got this run.