class, which creates various restrictions on weapons and armor types available to that player, and also grants special abilities. For example, the bread-and-butter Soldier class has medium armor, medium speed, and a well-rounded selection of weapons and grenades, while the Scout class is lightly armored, very fast, has a scanner that detects nearby enemies, but has very weak offensive weapons. One of the other differences with CTF is the fact that the flag is not returned automatically when a player drops it: running over one's flag in Threewave CTF would return the flag to the base, and in TF the flag remains in the same spot for preconfigured time and it has to be defended on remote locations. This caused a shift in defensive tactics compared to Threewave CTF. Team Fortress maintained its standing as the most-played online Quake modification for many years. Team Fortress would go on to become Team Fortress Classic and get a sequel, Team Fortress 2. Another popular mod was Threewave Capture the Flag (CTF), primarily authored by Dave 'Zoid' Kirsch. Threewave CTF is a partial conversion consisting of new levels, a new weapon (a grappling hook), power-ups, new textures, and new gameplay rules. Typically, two teams (red and blue) would compete in a game of Capture the flag, though a few maps with up to four teams (red, blue, green, and yellow) were created. Capture the Flag soon became a standard game mode included in most popular multiplayer games released after Quake. Rocket Arena provides the ability for players to face each other in small, open arenas with changes in the gameplay rules so that item collection and detailed level knowledge are no longer factors. A series of short rounds, with the surviving player in each round gaining a point, instead tests the player's aiming and dodging skills and reflexes. Clan Arena is a further modification that provides team play using Rocket Arena rules. One mod category, "bots", was introduced to provide surrogate players in multiplayer mode. Arcane Dimensions is a singleplayer mod. It's a partial conversion with breakable objects and walls, enhanced particle system, numerous visual improvements and new enemies and weapons. The level design is much more complex in terms of geometry and gameplay than in the original game. There are a large number of custom levels that have been made by users and fans of Quake. , new maps are still being