"The center of the portal also housed the "berserk" power-up item, which, just like in the original Doom, lets you completely obliterate your enemies with a single punch. Considering that many of Doom 3's levels will be more tightly knit (and offer less room to run away) than the larger levels of Doom II, berserk seems much more dangerous, which is apparently why it's also so obvious. Picking up the berserk item causes your character to briefly go insane--you still have complete control of your character, but your screen flashes red, like in the original Doom games, and your character screams at the top of his lungs (which is audible from a distance) and is surrounded with glowing red rings."