Wikipedia said:Skulltag is one of the multiplayer-centric Doom ports that is based on (G)ZDoom. In addition to client/server networking code, Skulltag includes bots for offline multiplayer games; new game modes such as Capture the Flag, Skulltag, Invasion, Duel, Survival, Teamgame, and others; as well as new weapons, monsters, items, powerups, artifacts and gameplay-modifiers such as Instagib (a spinoff of Deathmatch where all players spawn with a railgun that gibs other players in just 1 shot). Skulltag supports Heretic, Hexen and partially Strife, and the package also includes a server browser, the Internet Doom Explorer Skulltag Edition (IDESE), for joining online games in progress. Skulltag also features enhanced graphics, such as OpenGL rendering (based on GZDoom's renderer), high quality resizing, and support for HD screen resolutions. It also has support for models and high-resolution textures. Skulltag also features its own resources for map editing and such.