"In addition to the level editor, other mod tools for Doom 3 include the sound editor, the script editor (all the AI in the game is handled by Doom 3's script code), the particle editor, the articulated figure editor (used to create ragdoll skeletons for the game's character models) and the GUI editor. Duffy said the editor was actually created by Raven Software for their work on Quake 4 but that the editor is a bit crashy due to id Software's own work on the GUI code (most of the GUI code is done by hand in Notepad, according to Duffy)."