Hey! Congrats on completing the jam!
While I understand the idea behind your game, there are some things that you could improve:
- Controls. As many people said before me, there are problems with jumps :D I guess that your 'isGrounded' variable gets resetted every time the player collides with any wall, so when you hit Space you can jump infinitely. I don't know which method to check ground you are using, but my guess will be to give your walls a different tag/layer than the floor. And, again, as many people said before, the player's speed increases too much during the jump, so that I didn't even have to use platforms in Level 3, I just jumped them over without even touching;
- Visuals. I think it is not a bad thing to use simple figures and even primitives. It gives a minimalistic look to your game, but in that case you need to make your visuals stylish;
- Perspective. I guess this thing can be very subjective, but it was very tough for me to tell the depth of where my character currently is in the scene. So often I ended up jumping to a platform and falling, and then realising that it is a bit more far from the camera than my character is.
Anyway, good job and keep it up!