CstDoom3 is a gameplay mod for Doom 3 and Resurrection of Evil. All new features are optional (opt-in) and can be configured using the menus.
Game Options (main menu). The game options are organized in groups, and only the options of the selected group are shown. The name of the selected group is displayed in a bar at the top of the window. This bar is actually a button that toggles between the options of the selected group and a list of groups. To select another group (so that its options are displayed), click on the bar, and then click on the name of the group that you are interested in.