This was decent. I appreciate that showing the platforms also stops the player. Unlike a lot of similar concepts, this feels like a memory game on purpose instead of on accident.
The audio needs balancing. The switch and death sounds are much louder than the music or jump sounds.
It is possible to press off and on at the same time, which biases towards "player off" and produces an awful crackling noise. There should probably be some kind of buffer requiring the player to un-press the control before they can re-press the control.
While the physics are fairly competent, especially for a first platformer, I think the turn-around should be a bit faster. While it's usually fine for momentum-based platformers that the player stops slowly when nothing is pressed, the problem is that the player also stops very slowly when the opposite direction is presed. While this can be a valid mechanic under the right contexts, it's usually very unintuitive and, in this case, makes the player feel out of control.
All in all, good attempt.