ScoreDoom is a fork of GZDoom 1.0.29 developed by BilboHicks to add an arcade style scoring system to Doom. Points are scored when shooting/killing monsters, achieving map objectives, finding secrets and map items in the quickest time possible, with bonus points for maxing tallies or getting under the par time. The port actually consists in two different programs: one, GZScoreDoom, is intended for single-player game; the other, ScoreDoomST, is only to be used in multiplayer. The latter was created as an outcome of the release of Skulltag's source code for the 97c2 version.
In single-player, each wad/wad-episode and level has its own high score which can be set. A single-player is allowed to log in to a score server which keeps track of the high scores for the IWADs and many famous mods. In co-op, each player competes to score the most points on a map, or across a whole wad, where the competing scores are clearly seen. A points-spread stat is also visible to tell players how far behind the leader they are. ScoreDoom supports up to 4 player co-op. High-score servers are not available for multiplayer.
ScoreDoom also has an optional add-on pack, which adds well over 150 new monsters, an arcade style announcer, many new powerups and a new weapon to augment the regular Doom menagerie. This content was previously created/made available by other members in the Doom community. Using the add-on pack also turns the boss fights (in the ExM8, E4M6 and MAP07 levels) into "boss rushes". There are different versions of the add-on pack, one being made for GZScoreDoom and the other for ScoreDoomST.
ScoreDoom is based on old versions of GZDoom and Skulltag, corresponding roughly to the 2.0 branch of ZDoom in terms of supported features. Content intended for newer versions of these ports is not supported and may require to be modified before it can be run. Furthermore, while based on engines that support Hexen and Strife, only Doom (including Ultimate Doom, Doom II and Final Doom) and Heretic are considered supported: there is no score server for other games. The add-on pack itself is only compatible with Doom.