Whaaaaaaaaaaat. It's just so clever. And I have no idea how you coded that. Puzzle platforming is bold to do in a GMTK jam as a lot of people will do it, but you've managed to do something : original, with a good progression from easy to hard, and technically impressive.
One small UI element that wont affect my rating but : I could put the slider out of the screen and it's then hard to drag it back. You should constrain the X position between limits.