Ballista is a physics-based game that uses an HMD to immerse a player on top of a skyscraper, introducing its audience to the core concepts of mixed reality. Players use a physical gun to shoot virtual beach balls through holes in a physical goal. Each player is awarded a point for each ball that goes through goal with 60 seconds. The game was extremely successful in engaging the interest of, and exposing guests to mixed reality. Ballista was developed for the 2009 Otronicon event at the Orlando Science Center.