A modification of any kind to a game, attempting to improve its look and feel, its interface, its gameplay elements or its balance. Questions about custom maps, custom game modes, custom UIs or even official but temporary modifications by the game developers themselves fall under this tag.
As a followup to my earlier question, what add-ons are available to assist healers in end-game raiding? How do they work with limited screen real estate? (I already use Skada, BadKitty, DBM, ...
I just bought Left 4 Dead 2, and I noticed there's a "mutation" (mod) to play, but only one per week (I think it's per week). Is there a way to play past official mutations, or is it intended for ...