The art is super cute! Though the gameplay is a tad rough; here's some suggestions I have:
1) The movement seems super slippery, even without jumping. It's this slippery-ness that's caused me to slip into lava too many times, even when I've stopped hitting any buttons. Maybe try toning down the acceleration a little to give the player more control?
2) The jump is super jarring and fast. I'd recommend a tad more floatiness/acceleration to it; the jump combined with the already-slippery-ness makes some easy jumps super hard to do.
3) Love the parallax in the background, but it's a little too fast for me. Maybe make it a little slower?
4) This is a bit of a nitpick, but some of the ledges have a "lip" that makes it harder to jump on; I think the aesthetic is nice, so it's more of a collision shape fix than an art fix.
5) Finally, this is very much a personal preference, but maybe consider having the jump button be controlled by the up arrow key/w key instead of the space bar? I dunno, just a suggestion you can play around with.
Can't wait to see how the game turns out!