A heavy fog covers the map which forces playeres to use their flashlights. However, the flashlight's have a battery. You can only keep a flashlight on for a total of 1 minute. For example, you could keep it on for 30 seconds then in a minute you could turn it on again and you would have 30 seconds left on it. Also, all ammo capacity is cut in half to prevent players from spamming through the mist. This creates an eerie feeling as there could be a player right in front of you without you even knowing it.
Oh, you're right. My mistake, I thought it was completly original. I had a little slip with a recording company on it called Season of Mist and I took inspiration from it. I didn't know it existed already. My mistake :/