The number of enemies has been increased to account for the number of human players, adding to the level of difficulty whilst providing a great change to the original game. To install the game simply use the one click install on the Steam store. The developers have done a brilliant job. I thought this would be a buggy and hacky attempt to integrate co-operative game play into these games. Note: You do need to own Half-Life 2 to play it.
Synergy tries to maintain the true Half-Life 2 game-play, while still adding in our own unique ideas. You may also install other third-party mods, such as MINERVA: Metastasis and ROCK 24, to also play them cooperatively with other players.
Synergy is the Half-Life 2 cooperative modification that enables you to play with others through Half-Life 2 and its episodes (Episode 1 and 2), as well as our own levels.
