Very nice and polished game, though a bit difficult and slow-paced! I had to look at the video guide in the comments to find the yellow gem, which was definitely a very big brain puzzle. Over the course of a bit more than 2 hours, I managed to find 23 out of 24 coins and 1 out of 2 stars, as well as a smiley room.
The graphics are simple but pleasant, and both the artwork and the soundtrack are a good match for a puzzle game. My only complaints are that the green and teal blocks are a bit too similar, and some sound effects for the player jumping and landing, as well as blocks being created, pushed, and destroyed, would really complete the game.
The movement is nice, though I wish both the player and the blocks were a bit faster. I often found myself using the anti-softlock feature simply to go back to the beginning, since it was faster than running all the way across the map.
Still, I had a lot of fun solving the puzzles, and the game overall feels very complete for a gamejam project. Excellent job!