Minecraft was designed almost as a joke, but has taken the world by storm. People of all ages have built all kinds of crazy things, from enormous cities and castles in the sky to deep, dark dungeons.
There are two ways to play -- Survival and Creative. Survival mode has some violence, there's no blood. A few blocks fall apart -- that's about it. If your kids choose to play Creative Mode, there's zero violence because the goal of that mode is to just build whatever you want!
Another good thing about this game is that your kids can play together, which makes building go much faster!