The variable jump was a good addition, game jam platformers sometimes omit that.
I think the lighting was not done well. You had a black sprite on a dark background and then added seemingly arbitrary shadows on top of it. This just further obfuscated the player character, which should stand out more than any other object, especially in a tricky platformer.
In the very first puzzle, you have a wall nearly blocking a jump. That wouldn't be bad except that the character would sometimes get stuck on there.
The game was quite ambitious, using lots of physics, but your levels should introduce one mechanic clearly, before combining them. The complete lack of instructions didn't help. It wasn't clear what the some of the levers did.
Some music would have helped the atmosphere, I assume you were going for something moody.
Good effort, but think carefully about each level and why you are using the colours, lighting that you are.