Hello!
You're off to a good start!
Several thoughts:
+ There are some cool ideas, each level offers something new
+ controls feel smooth and responsive
+ Switching characters to move forward is interesting
- Glitchy interactions with slopes or moving objects (character can be pushed into terrain or glitches while standing on the slope, constantly twitching)
- a lot of backtracking to switch characters on lvl 2 (lvl 4 was OK in that sense)
- everything is tiny, some thin walls or elements are hard to notice and blend with the background. I didn't notice there's another character to play with until I accidentally touched it
- Stuff is functional, but there's very little feedback for player's actions - character switch/death/interactions are not highlighted at all
- Some level elements are hard to navigate (not in a fun challenging kind of way)