This level can be pretty difficult, even for experienced players. The initial darkness, then later the darkness in section three, and speed of the zombies as the level progresses will test your skills thoroughly. However, using a level design exploit you can make your go of this final part of the game quite easy. The video here simply illustrates the location of the exploit. A maximum of 15 zombies can spawn in the first two rounds of this level, no more than that. By grinding and collecting bullets in-between spawnings, you can amass a fortune and tons of kills. This does nothing for further unlocks, but using this spot enables anyone to have a chance at the final boss. As the video shows, the location is a pile of debris with two boards sticking out of it to the left of the main room you enter. Standing on top of this the zombies will NEVER touch you in the game's current build. You can sit there and kill them all without ever having to worry about dying. Since someone else already did a walkthrough I didn't show item locations but can add another video if needed. For the basement round (the third part), which is not shown, simply lure the zombies back up to the same pile and kill them as you did all the others. The final round must be beaten as-is because it takes place in a different area and requires you to locate Dr. Fleshenstein's brain repeatedly to kill him.