PC (Microsoft Windows)September 1, 2005
Released ✓ 
RELEASES · DEALS · SUBSCRIPTIONS
Synergy
Synergy is a Half-Life 2 Modification that enables you to play through the Half-Life 2 series and many other 3rd-party campaigns cooperatively with friends.
ActionScience fictionPlatformShooter
Game modes
Co-operative
Player perspectives
First person