I'll admit I didn't quite get through the whole thing, as the controls (as others have mentioned) were just too tough for me to get around. I gave it a good ten minute go, though, so here's a few direct notes:
-Controls are first priority in a platformer. In the future, look into interpolating the player velocity rather than setting it directly, and unless you're going for super-tight controls, give the player some momentum in the air when they jump.
-As has been said, the player iFrames are almost non-existent, leading to some situations it just didn't seem I could get out of (being juggled by a crab-thingy was a highlight. Well done, crab-thingy.)
-In a game like this, giving the player either a camera they can look down with, or making pits you can fall down and survive have visible bottoms from the platform above, are both excellent choices. Players want to know where they're going, contrary to how fun "leap of faith"s seem to us making the game. We already know what's down there, they don't.
Overall a great first-time effort, excellent job finishing the jam and getting a playable game into our hands. Thanks for making it!