Overall was fun, though a few annoyances.
1) Health did not regenerate. This was mainly a problem in that falling into lava gave you a second to get out and live, but due to no health regeneration required you to have full health. This led to the best situation if you lost health to be try to find a checkpoint, then suicide.
2) Checkpoint did not function. Small gripe here, the checkpoint before the elevator hatch/overcharged instant kill level has a checkpoint. Dying after using it listed "your bed is obstructed or missing" and used the normal level spawn (IE the entire beginning). Only checkpoint I had this problem with.
Also, I noticed the game 'ended' after 4 levels, but using creative mode and flying around I found what looked to be a almost entirely functioning 5th level labeled as the 4th (zombie fortress explody one), a 5th one with nothing yet in it, and a giant arena meant to fill with lava. Somewhat neat, but wondering what happened since the exploding fortress one sounds like something implemented but I could not find a legitimate way inside to begin the world.