co op for the hat please anyone?

help me do 2 co op missions plz

Hey I just got this game the community seems pretty dead though. If you are interested just comment on this forum.

Like I was just looking at steamcharts and I noticed that original Alien Swarm has more active players then Reactive Drop I am not here to "ohhh this one is better then this one" type of bull$hit - I am just geniuely curious what is the reason for this phenomena I played a lot of Alien Swarm back in the day but nowdays I really like the Reactive Drop version more so I am curious why people choose this one over RD your honest opinions...

i'm wanting to get the achievement hat trick but id also like to learn more about this game from people who actually play it