NationStates is a browser-based simulation game in which you can create your own nation. I’ve used this in classes before, and it’s a great way to get students to think about what “nation building” means and leads to good discussions and debates. Can be played individually, or you can set up teams to work on creating one nation together. Some of the language used in the descriptions is rather colloquial, but the site has lots of possibilities.
Here is the tutorial I made for students last year to help get them started: