to use your flashlight. The lighting is very bad (either dark colours, or not a lot) to give you a scary feel, along with some zombies, demons, and creepy sounds that play through-out the level. It has A LOT of enemies to fight, most of the demons teleport in, and most of the zombies hide around corners. Plenty of weaponry and health/armour to help you along the way.
The map is quite cramped most of the time so you'll have a very hard time taking down some of the bigger fights that occur. Also, this is a maze, so there are a few wrong turns, but they often yield something beneficial (whether it's armour, health, ammo, or weapons). Leave no corner unsearched, because I probably hid something there. All-in-all, I tried to give a classic doom feel (except for the extreme darkness), sort of like the map 'Hunter' from final doom or doom 2, I can't remember. Have fun!
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