Really nice mechanics and puzzle execution. The shift in soundtrack (when you shift between platforms) is also nice and well-executed.
Some feedback:
- I've found a bug: sometimes, when pressing SHIFT, you immediately die and are reset to the last checkpoint.
- Have you ever heard of "coyote time"? Basically, it means that you still allow a player to jump, even if he's at the edge of the platform (or slightly over the edge). I've failed stages twenty times because I pressed jump when I was near the edge of the platform, but the game thought I was already falling off, so I died. To be honest, became quite frustrating after a while :p (Another solution would be to make the player walk slower, so there's more room for error when pressing JUMP. Not my preferred solution.)
- Some sort of menu/way to quit the game would be nice. (Now I had to pull tricks to force quit the game.)
- One of the first puzzles (the one with the gem up high and the platform that moves upwards) could use a checkpoint halfway, or be slightly less difficult. It was a great puzzle/challenge, but maybe better suited later in the game.
Besides that, great game and great gameplay!