The basic idea is:

• Invite a friend to vote, you get a point
• Post a video about the need to vote, get 2 points
• Post a video proving you have voted, you get 10 points
• Bring a friend to vote and post a picture proving you both voted, you get 20 points
• Write a post explaining your position on a topic, you get a point.
• Write a post explaining a political party's stand on a topic, you get 2 points.

Essentially, you could take the game of Farmville (or something like it) and turn it into an a game around the act of voting, and potentially other acts of civic engagement. Make it fun to vote, so that the 20 or 30 minutes to do it doesn't seem like a chore.