Synergy

Synergy enables you to play through the Half-Life 2 series and many other singleplayer Source Mods cooperatively with friends.

App ID	17520
App Type	MOD
Developers	Synergy Team
Categories	Multi-player, Online PvP, Co-op, Online Co-op, Partial Controller Support, Cross-Platform Multiplayer, Steam Workshop, Includes level editor, Captions available, Valve Anti-Cheat enabled, Includes Source SDK, Mods, Mods (require HL2)
Genres	Action, Free to Play
Release Date	3 Oct, 2008