Custom / Concept, by 
Time for a more to-the-point review system.
Description:
Dodge and don’t shoot the spike bolls, and don’t get hit too much by the enemies (you can shoot those, however). Moving right automatically at a fixed speed, you can’t slow down or speed up, only jump. Your health slowly regenerates when you aren’t getting hit. The level is pretty easy once you know where everything is. Relatively short.
The good:
Experimenting with a different way to play JJ2, looks decent. Music fits.
The bad:
This level suffers from a lot of unintuitive design issues such as:
Getting rid of the hurt sound and replacing it with the burn sound. Replacing the sound with something that is asscociated with killing an enemy is misleading. With the new health system, it can be easy to overlook if you have F9 on a lot out of habit (it overlaps, which could be remedied by moving the health where it usually is).
The trial and error nature of this level; This comes down to many things; failing to mention shooting/going into spike bolls kills you until you fail, the forced tiny resolution, making copter ears useless (everytime I used them I died into a spike boll because I couldn’t see what’s ahead) and shooting then suddenly discovering there’s a spike boll off-screen. Being mindful of shooting isn’t a bad thing, it’s that I can’t always prepare for it until I know what’s ahead.
The cutscene that barely suggests it’s one, because it looks no different from than what you are playing. Perhaps some black bar surrounding the bottom, with the character saying not to shoot the spike boll/s in some way? Maybe there could be some explosion sounds going on at the start and end.
Why am I walking away from an explosion? It looks odd, as wouldn’t you be running away from it? Plus it suggests that you can go faster, but apparently this level does not.
The annoying bug: Backspace doesn’t work. So you have to keep reopening the level everytime you fail. This is exactly what makes me discourage from recommending others to download it.
Could improve on
The level is rather short. It lasts 30 seconds. Though it appears to be intended, so I don’t imagine that changing.
Being able to control your horizontal speed would be more suspenseful and challenging. It would make the lab explosion itself a threat (like if you fell far too behind, you’d die).
Difficulty settings could affect the level.
The script writing. Too bad I’m a script noob, though I can say, there appears to be a lot of uneeded hardcoding, which results in a wall of text.
Once these issues get fixed (especially the backspace one), I’ll rate it higher. EDIT: Forgot to mention something else.