A work-in-progress version of Doom 3, called the "E3 Demo Alpha" (also known as the "Alpha version"), was placed onto the Internet in late 2002. As with most video games, this work-in-progress version differed from the retail version in several aspects. These differences include, but are not limited to, the following: * Graphics for the Heads-Up Display (HUD) * Models for the weapons & enemies * Sound effects for the atmosphere, enemies & weapons