Loads of fun! And a great use of physics. It struck me as odd that some levels only used certain mechanics once (the spike balls, gravity flipping a midair box, the jump flip), but as its your first intro to a game I think you have a great foundation! I think a platformer works best when it feels good, and I felt the jumps were excellent, but things like nudging boxes to the spots I needed them to be was finicky. It was also a bit difficult to time when I could do the jump flips. Level 13 was quite tricky, but fun to figure out, hehe. Great work, and great use of kenney's lil sprite maker! I love those lil guys xD