Second room killed it for me. The small amount of lag caused by having the game fullscreen made the penultimate jump through the second batch of red stuff onto that little box and then up to where the last two collectibiles are literally impossible to pull off.
I was able to complete the jump after minimizing the game and finishing the level in-browser. But it reminded me why I don't like puzzle-platformers. If a small drop in frame-rate was able to make a jump impossible now, it's only a matter of time before I'm doing some tricky jump later on in some advanced stage, and a lag spike kills me somehow, and I have to go alllll the way back to the start of the puzzle.
It's not your fault. I just don't like this genre.