Space Station 13 is a paranoia-laden roleplaying game set against the backdrop of a nonsensical, metal death trap masquerading as a space station.
Read more here.
/tg/station 13 Community
Main website for the /tg/station13 community is http://tgstation13.org
There are several /tg/station13 servers, all hosted by MrStonedOne. They all operate /tg/station13 code.
Download BYOND to play.
Check out these maps that come packaged by default in the game.