It's Dwarf Fortress for those of us who were always interested in its concept, but couldn't get through the ASCII wall and the learning curve, in a space setting that's heavily inspired by Firefly (so there are a multitude of worlds with varying degrees of technology advancement, and you're going to see people from all sorts of backgrounds). You're in charge of guiding a group of colonists through their trials and tribulations in one of the titular Rim Worlds; distant, isolated planets lacking in strong central government and low in population density, and your job is to get them to stay alive long enough to... do whatever you want, really. There is a clear "end game" goal here (build / access a ship and escape the planet), but the real fun of the game comes from developing your base in whatever way you want, for as long as you can, while surviving the ever-escalating threats that the AI will throw at you.

Both in art style and construction-oriented gameplay, the game is immediately reminiscent of Prison Architect, but Rimworld is much more than that, as it's also packing a surprisingly deep combat system that demands careful planning, both while building and during combat itself, if you want your colonists to live to see another day. The AI "storytellers", a concept not unlike L4D's "director", ensures that you meet a level of challenge that, at the very least, will give you a memorable tale to share after your colonists' demise.

And when the time comes and your colonists die, you WILL feel it. There are many, many easy / dumb ways to die in this game, and learning about them is part of the experience; you'll just HAVE to tell your friends about the one animal handler who died in combat, only to have one of his pets go mad from grief and butcher one of your colonists, or the colonist that sacrificed his life so you could learn about cave-ins the hard way, or the dangers of running a drug operation in a colony full of stressed people fearing for their lives...

If there's one negative aspect about it, it's the fact that its tutorial is simply not good enough. Many important mechanics are barely mentioned or not even touched upon (setting work priorities manually is one such glaring omission); losing colonists because of mistakes you're aware of or gambles gone wrong is fine, but having them die because you didn't understand a part of the UI is frustrating, and there may be a lot of that if you don't go looking for tips before diving in too deep.

Overall though, it's an amazing game. It's in Early Access not because of it being a buggy mess, unplayable or imbalanced; it's simply there to let buyers know that there's still more content being added to it, and the end of early access will mean the end of development for the game. I can't recommend this game enough, it's absolutely worth it at full price!