I like the checkpoints. There are checkpoints, by the way. What I would really like is a way to save progress so I can close the browser window and then later still restart from 1434. I also liked the way you made it 1:1 between the mouse movement for a jump and the distance traveled by your head. Some of those propeller obstacles, though. Hard to get anything going sometimes. It was also frustrating to want to do two jumps in quick succession, only to have the second one come out as a slide instead.
All that said, I'm still playing it, and I came back to it after sleeping. Good stuff.