I tried to play MP with a friend and we've never been able to connect to each other. Ports are open/forwarded and I really don't know why we timed out all the time. We tried both directions.
So it would really be much better if we could just host a game and join via Steam friends system because that always works unless you sit behind a really tight firewall.
I buy my games on Steam only and please don't take it the wrong way, but I kinda expect games to use it. Don't mean to be rude, but you know... entitled customer and such
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So if it is somehow doable without too much work I'd really appreciate if that is put in later on, even if it is after release.