Alien Swarm: Reactive Drop

Alien Swarm: Reactive Drop extends Alien Swarm, bringing more of everything: maps, aliens, game modes, guns... And most importantly Steam Workshop support.

• Tactical co-op for up to 8 players with a top-down perspective
• Steam Workshop support for community maps and challenges
• New co-operative campaigns
• Challenges: Modifications of the game, just like Mutations in Left 4 Dead 2
• PvP: Deathmatch, Gun Game, Instagib, and Team Deathmatch
• Singleplayer: Play with improved bots on all our official maps
• New Aliens: HL2 antlion guards and more
• New Weapons: Desert Eagle, Devastator, and Combat Rifle, with more to come
• Over 100 Steam achievements
• Leaderboards: compete with your friends for the fastest mission completion
• Improved spectating: see hacking minigames and mouse movements in real time

Source: Steam Store Description