There's no real mention of how the game mechanics are integrated. It's not really risk if it's simply "the most checkins wins." No element of chance. Could still be early in the game however.
- If you checkin and your borough already owns that neighborhood your checkin adds a defender to the neighborhood.
- If you checkin and your borough doesn't own that neighborhood, your checkin counts as an attack.
-For an attack we do a dice roll, and based on that dice roll you take out X number of defenders. If your checkin takes out all the defense then your borough now owns that neighborhood and you become a defender.
As the user base increases we'll definitely be tweaking things, but the element of chance is huge to us. It's what keeps things interesting.
http://www.betabeat.com/2011/06/29/fourcraft-turns-your-chec...