1-12 Player Online Game. Similar to the Trouble in Terrorist Town that is in Garry's Mod. Try to survive by figuring out who is out to get you!
why use 4 number or letter codes just make it easy like 1 and if 1 is being used or is full then 2 and if that is the same then 3 then on
and on
Then other players could guess your private lobby codes, and the intention is for friends not to have strangers join their lobbies. I think 4 number codes is fine, even 2-3 number codes would be okay too though but its nitpicking