The idea is fun, the game isn't too difficult (which is good). I like the music, a bit borring after some time but the rythm is there.
As for the gameplay, it's fun, but slow and movements are a bit too "soft", maybe crank up the player acceleration. As other have pointed, try to add check points.
I encountered a few bugs:
- The man at the bottom of the screen fly when the camera goes up in level 2
- I couldn't end the level 2, you fall but the camera doesn't follow you and you don't die, then the other character goes to the left. The blue portal next to him doesn't work
- If you move against a wall, you can't jump .
The art is... not the strongest point xD but don't worry, you'll get better (practice is the key)
Somes tips for your art:
- At first, simplify things, use few colors and use simple shapes. let the creativity of your player do the work, you will have more time to focus on composition. A glowing cube of color in a white world on a black background can give a really good result.
- Make more variations, your background is literraly the same texture as your tile, and you have only one tile type per level. You have to break repetition of paterns, rotating objects helps a lot.
- When animating isn't your thing, use the game engine, instead of an animation, make the character wooble left-right when moving, strech it when it jumps, flaten it when it lands. It's cheap and it give good results.
Always consider to continue working on your games, even if the jam ended, it's a good way to improve !