If you want to make a difficult level, don't use fake difficulty. "Up and down" is just ridiculous. The room itself is very hard, and when you exit it, you'll fly straight on top of a disappearing platform, with spikes both above and below, and a checkpoint on the ceiling taunting you. So put a second checkpoint on the floor so that people don't have to do that room thrice. The same happens with "Highway to hell". Put a checkpoint on the platform in the corner in "Warm-up" to encourage players to go for it instead of staying still.
In the warp section, the warp destinations effectively have randomness to them. Many warps make you randomly spawn on a spike. The green room was all about hoping you appear above a platform in the last warp room instead of a spike. In the token hell room, I thought the warp from the middle room to the right middle room was a death-warp because I flew straight into the warp to the death room below. Require less precision.
I could see the difficulty get easier. You did succeed in that. Hairpin wasn't as bad as it was hyped up to be. But there's no need for the first floor to be empty. The second floor contains the classic "difficult room" gimmicks, backsliders and high-frequency enemies. It should be simple to create easier rooms than that which still require something more than running.
