"Much was made on the planned support for mods in Doom III. Duffy said that nearly everything in Doom III was text file based so that should make it easy for mod makers to pretty much do whatever they want in the game. The game’s development tools will be included in Doom III’s release and Willits said he expected that there will be a ton of mods made for the game in a short period of time.

Willits said that the physics engine for Doom III is a unique id Software engine and is not a licensed engine like other games have. Willits described a Doom III test map where 100 boxes are stacked up and one shot can bring the entire stack down. Willits claimed such a scene would bring other game physics engines down to their knees."

"Q: What key features will separate Quake IV from Quake 3?

A: Quake IV is a continuation of Quake 2, back on Stroggos fighting the Strogg in the single player. They are planning different types of gameplay such as vehicles and other elements."