I think because the macOS and browser version had the same name, itch got them confused and was trying to use the macOS version in browser, causing the error. I have uploaded a differently named browser version that should work now.
I don't know exactly what you mean by "fever-dream."
My goal in making this game is to demonstrate the idea handicapped persons can leave the world a better place. I was inspired by a good friend :) My friend is politically active and told me that I had to put gender roles and police brutality in the game for the cripple to fight, so I tried to find a way to represent this visually.
Regarding the issue getting up slopes, I noticed this too. I believe it's due to the way gdevelop handles collisions between objects at different angles (I could very well be wrong). I had thought of trying to fix it, but after thinking for a while I thought it added a bit of realism to the game. If you've ever ridden in a wheelchair, you'll notice that it's sometimes hard to get up slopes, and if you go to fast you'll lose traction and get stuck. The slopes are the same way - if you go to fast you'll slide backwards, but if you slow down you'll chug right along.
Unfortunately, like the audio, there is no way to win or lose, although you can improve your high score :)