A really interesting set of mechanics with a TON of expansion potential. I especially like how a "run" is broken into 5-minute sections and effectively goes endless, with each setting change serving as the difficulty bumper.  An amazing 12-day prototype that deserves a second pass to refine the rough edges, and on that front I do have some suggestions:

• - The early game progression feels sluggish, especially for newer players who haven't quite gotten their head around the "break drift to strafe" mechanic yet, so maybe a temporary "super magnet" for experience during the first 2-3 level-ups would help that.
• - The movement being mouse-based is a great idea, that said I think it'd take better advantage of the medium if, say, there were upgrades that added quicker-responding movements, such as sharper drops to the ground when airborne accelerating, or faster/instant course-correction when changing directions.
• - There's a thing I ran into on the "green hills" biome; there were spots where if I hit accelerate while facing away from the map edge, I would instantly go to max speed & shoot like a dart. I think this is a bug that could be upgraded to feature, perhaps surround the play area with a "repel field" that forces acceleration in the direction away from it but fires the player at super speed. I was using it on purpose as a way to escape an incoming horde, so I think it works as an on-purpose survival mechanic.

All in all a really cool proof of concept and something I've been noodling with on the side for like 20 minutes or so every day since I've gotten it. Give it a try!