I really enjoyed this game, beat all 20 levels! The platforming gets really tough towards the end! Love the consistency of the art style, music, and sound effects. I'm not a big fan of the moving left speed being slower than moving right, but at the very least the platforming is designed around that mechanic so it's not something that feels unthoughtfully thrown in for artificial difficulty. Overall though, great job!
Also, special tip, on level 17 you can move the spring to left and jump to the key instantly