Critiques up first: I would recommend updating the control scheme to something more comfortable like WASD instead of arrows, folks who use a 60% keyboard don't exactly have an easy way of controlling the character left and right with arrow keys being mapped to a secondary/function layer.
Character physics feel a little too still, id like to see some sliding and easing into movement to smooth it out.
The knockback is a little too punishing for how tight the platforms are and how stiff the movement is, since we aren't managing health or an attack, enemies aren't really worth implementing outside of just annoying the player. Setting up a challenge for the player to platform through can be done without relying on an enemy.
Some greater visibility into how the puzzle interacts with the world would also be a bonus for readability into your actions. i.e. zoom the camera out a bit when engaged with a puzzle, the second stage has a reusable puzzle platform for two heights, as a player, I kind of want a better preview of how I should be planning my platform layout if I don't have to solve the puzzle twice if I fell off.
Game is interesting concept, would actually like to see the next iteration of this if you plan to continue to polish.