Number of stages: 4
A mutated sewer would make it into the original and final versions of the game. But the first two stages of this round seem to take place in a normal sewer, something that seemed to get dropped from the original version.

This round is set in a sewer. The clipping in this level is pretty awful, with Joe falling into bits of the floor constantly, so be prepared to jump a lot.

You'll eventually come across some kind of wiring that you can't interact with. There is a part towards the end of this stage where you'll have to kill several soldiers and ninjas.

The second stage is more of the same, just now with a difficult platform section. You can run under the platforms, and whilst you can jump up to the top of them, it is difficult. The only enemies here are ninjas and soldiers.

The next stage is in a mutated part of the sewer. The only enemies are ninjas and soldiers once again. Around halfway through the stage the background will change, showing heavy mutation.

You'll have to drop down a bit to get any further, and the background will eventually change back to normal. You'll be near the exit when you see a soldier standing in the air.

The last stage of this round is the boss fight. When it starts, the boss won't be there, but just walk a bit to the right to see him. Unlike most of the other bosses in the prototype, this one doesn't do anything at all. His lower jaw is missing entirely. The sprite for this boss is actually in the room several times -if you use the float jump to get over the first boss sprite you see, the round won't end. Drop down and start running right to find more boss sprites, which also do nothing.