Basically Dwarf Fortress lite I guess. The major differences include being set in a sci-fi scenario as opposed to fantasy, being slower and this game will try to kill you as opposed to Dwarf Fortress. Oh and as this awesome post from bay12 forums puts it – ‘Forgot rimworld colonists arent dwarves and my colony is in ruin because of alcoholism and liver disease’
The biggest issue I have with the game right now (in EA) is the UI. It just doesn’t communicate a few things well. The caravan deployment screen (to add people to the caravan I have to press the X button? The rot timer only displays the lowest value and not how long the caravan can last in total?), the lack of a event log (I accidentally dismissed an event, now finding it is a pain…), losing the settlers’ info view when accidentally misclicking on something else when looking through each settler just to see their stats and other small things can be quite annoying at times. Also would be nice if the game had some sort of encyclopedia in it and I didn’t have to rely on an online wiki page that might or might not be updated when updates come out.
With this game, it starts off difficult, the controls are difficult to learn, but easy to master afterwards. You will easily form a love-hate relationship with this game, since you can easily pour in countless amounts of time into this game, into one colony, to have it all be destroyed by pirates, raiders, angry animals, natural disasters, or a pack of man-eating bunnies that catch your people off guard. This game is truely amazing as it brings out the worst in people, as they do actions that would be considered cruel, or would be just staright up crimes against humanity to survive and propser as a colony. Within one week, I poured 20 hours into this game, with it quickly becoming my second most played game, but one of my newer purchases in comparison to my most played game. Would definitly reccomend this game to anyone, as it can be used for a quick 30 minute break from work, school, etc. or can be used to fill up an entire day. The possibilities are endless in this game, every single colony I have ever made has had a different experience, different difficulty, and most importantly a different emotional connection to me.