Light is a big mechanic in Doom 3. The game loves to hide enemies in the gloom and turn the lights off on you when you least expect it, making aiming difficult and ambushes far more dangerous. The original game gave you a flashlight you could switch to, a heavy hitting melee weapon that illuminated a significant area in front of you but robbed you of the ability to attack at range. This forced you to tactically use the flashlight to briefly get your bearings before trying to take out the foes about you.
A semi-regular complaint about the game was that the flashlight mechanic existed, leading to various ‘duct tape’ mods that attached them to all or a selection of your weapons. The BFG Edition removes the flashlight altogether, replacing it with an armour-mounted one that can only stay on a limited time before recharging. It’s a pretty decent compromise, forcing you to to keep an eye on how long you’ve had it on, but I personally would have liked the option of taking the actual flashlight along too.
Regardless, light – and the lack of it – remains is a mechanic that not only builds up the tension, it gives the game a uniqueness in the series that has yet to be replicated.