1. can the gog version play with steam version?
2. does this game uses a centrelized server, or is it connect to ip/lan?

Thanks. Now the gog sale is over. Maybe this year it'll get another nice discount.

Anyone have luck setting up a network co-op between two machines on a local network? The host shows the external IP address (???) in the game menu, but the client connecting can never connect, regardless if I use the real/local IP address of the host, or the external one the host thinks I should need.

Both machines running OS X 10.11.4.

Opened a support ticket w/GOG, and received this information. None of it helped me, but might help you. Both my machines are on the same local network and neither have the firewall enabled, yet I can't join a locally hosted game regardless what machine hosts it, even if I use the local IP address (which is not what the host game shows--it shows my network's external IP)

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1. Please use the local IP address:
http://www.wikihow.com/Find-Your-IP-Address-on-a-Mac

2. Please make sure that both computers are connected to the same local network.

3. Please make sure that the game is not blocked by the firewall:
https://support.apple.com/en-us/HT201642

4. Please also try contacting the official support for the game here:
spacegame2012@gmail.com

I used a program called Evolve with success over my LAN. You just have to start a new session or something with the program, and it gives you a new i.p. that the other computer can connect to even though you are on the same local network.