deathmatch was both the most influential and most popular mode, Doom's co-op gameplay was also significant. Up to four players could travel through the entire game together, playing on separate computers over a LAN. The game's campaign mode was designed primarily for single player, but the difficulty was tweaked to compensate for extra human players. The following three games produced by id Software (Doom II, Quake and Quake II) all featured co-op modes. Some of these first-person shooters employ cooperative gameplay, where many players are joined to reach a common goal. However, some first person shooters do not make use of cooperative gameplay. Starting from the early 2000s, however, many FPS developers have forsaken co-op campaign play, opting to focus more purely on either a more detailed and in-depth single player experience or a purely multiplayer game. Epic's Unreal Tournament series had shifted almost entirely towards deathmatch modes, and significant FPS releases such as Doom 3, Quake 4, and both Half-Life titles shipped without cooperative gameplay modes. However, with the Gears of War franchise introducing the "Horde" four-player cooperative mode, it has undergone a resurgence, starting a trend which included Halo 3: ODSTs "Firefight" mode and Call of Duty: World at Wars "Nazi Zombies" mode. More games in the genre from the 2010s include the Payday and Destiny series. Role-playing games Most early role-playing video games were inspired by Dungeons & Dragons, but were restricted to single player due to the technology of the era. The earliest RPGs featuring something resembling co-op play were MUDs, which would later evolve into the MMOG genre. In 1989, Image Works released Bloodwych for MS-DOS and various other platforms which featured a two-player cooperative mode via split screen where 2 players needed to cooperate in order to solve puzzles and eliminate enemies. Later PC RPGs became more powerful and flexible in simulating the shared real life RPG experience, allowing players to collaborate in games over the Internet. Blizzard Entertainment's immensely successful Diablo (1996), which incorporated Blizzard's online matchmaking service, battle.net, allowing the game's players to play through the entire single player campaign together. The D&D-sanctioned Baldur's Gate and Icewind Dale games, released in 1998 and 2000, respectively, allowed up to six players to play through the campaign mode over a network. Atari's Neverwinter Nights (2002) was an official and comprehensive D&D simulator, featuring even more robust game-creation tools and developing a sizable online community.