Cool idea, I like it.

I think it could help if the Window would be bigger. Quite often, I would miss a jump because my Mouse went ouside the screen (above or below) and the plattform would not follow it anymore. 

I would recommend starting each time with the character paused in such a game. That way the player has time to move the mouse into position both in terms of cursor and in terms of actual rl mouse. The moving wall levels got awkward with how much I was having to move the mouse sideways.

I think some of these levels could've been cut. The drop down and jump back on thing got repetitive by the end.

This is a very cool game! I wanna see more. When the player spawns i think he could fall down after 2 seconds or something because it feels kinda bad dying because you didnt react to him falling fast enough

Quite fun! The character felt a little stiff, possibly just because of the lack of acceleration/deceleration or whatever, but yeah!