Very interesting. My first time through, I kept trying to control the gravity flipping, took a little while to realize it was random. The random gravity flipping was hard to deal with, but it suits the unstable theme well.
The art doesn't really tell a story that I understand however. Illuminati man is being attacked by the baseball boy mage with magic missile as he tries to complete the race? Not really sure what's going on there. Background is quite bland, which is good for readability, but not very interesting visually.
The vanishing platforms were a nice addition to the unstable feel as well.
Not really a fan of the music, it's better than nothing though. Could have used some sfx/stingers for a few things such as: touching the flag, being attacked, or being hit.
On the programming side the main issues I caught are that some of the heart refill code only resets your hearts graphically, like when you die to spikes. You keep your old health value. Some of the areas are lacking death planes around the level, so in theory you can end up way off the top of the screen. And it seems like the flags break if you try to play the game again after beating it once without reloading. Nothing really game breaking, as I did eventually fall back on screen, and the hearts do refill properly sometimes.
As for the levels, you had a mix of themes going, which was nice, though it was sometimes hard to see some important level elements (like spikes below you when you're standing on the ceiling) Nice to have an ending of sorts in the unique flag.
Congratulations on completing the jam!