“As pieces of the shredded starship fall around you, you start making plans to survive.”
The best way people can describe this is, is a war crime simulator. Which I agree with. However, there is much more to this than just war crimes. Rather than calling this a full on game, it's better to call this a story driven simulator.
There are a lot of things to do in this game. If you want to have a friendly colony that wants to help everyone, or at least as much as possible, you can do that. Or if you want to be a bunch of raiding pricks that harvest organs for money, that too is possible. Perhaps you just want to make a lot of money by producing drugs, that is also entirely possible in Rimworld.
Graphically it's not that impressive, however, it works very well for this game. The soundtrack however, absolutely fantastic. There are also tons of mods that can improve the game a lot. It's very likely that if you want something, there's a mod for it. There's also a bunch of expansions (of varying quality), each with its own theme. I'm personally quite a fan of the Biotech expansion, adding robots and gene manipulation.
This game is worth picking up if you want a sandbox-y game, and it's also best to go into this game with as little knowledge as possible, as losing is in fact fun. I could have said a lot more about this game, but you really just need to experience this yourself!