Rimworld has been in alpha since October 2013 but don’t let that dissuade you, it’s absolutely full of content and is only going to become better with every update. Alpha 14 is set to come out very soon, which also heralds the release of the game on Steam Early Access.
Alpha 14 looks like an absolutely huge update; the game’s UI has been greatly overhauled and new starting parameters have been added – one of which lets you play as a stone age level tribe. A bunch of new traits have been added (pyromania being one of them) and melee combat has been overhauled to allow players to block entrances with what are essentially shield walls.
Rimworld will be available for purchase on Steam on the 15th of July, but if you can’t wait that long you can get the game here for $30.