Rust is a punishing multiplayer survive-'em-up. It's harsh stuff - a hobbesian man-in-the-state-of-nature simulator that will literally melt you down for the fat on your bones - and that's what makes it great. You start out on the beach of a post-apocalyptic island with nothing but a rock and a torch to your name. You don't even have a scrap of clothing on. From there you'll forage and hunt to meet your most basic needs - warmth and food - before eventually working your way up to building your own base and putting together an arsenal of badass weaponry. To get that far, though, you'll need to survive the other players on the island. One way to circumvent all that pesky resource gathering is to kill someone and steal their stuff. Or maybe you could just steal their stuff and leave them alive. These are the sort of decisions you'll need to make, and that other players will need to make when they see you, in turn. It's these dynamics that effectively make Rust a story generator - the narratives that play out between you and other players are far more interesting than anything NPCs could offer. A lot of the time they'll end in murder, but every now and then a moment of human kindness breaks through. It's this harshness that makes Rust so rewarding when things start to work. If you can live that long, of course.
