This one was pushed to the patch1 branch. Now you can select a difficulty from the title screen by pressing + or tab (normally the difficulty would go up once you played every level in one go). At XXX, you can't recover from tripping at all!

I also added little hazard warnings when they're able to make you trip, as well as small "press down" tutorials to the early levels. Warnings won't appear in higher difficulties.

Oh, and I added another 10 frames of grace period while tripping. Just 'cause.