Sony officially unveiled PlayStation 3 (then marketed as PLAYSTATION 3) to the public on May 16, 2005, at E3 2005, along with a 'boomerang' shaped prototype design of the Sixaxis controller. A functional version of the system was not present there, nor at the Tokyo Game Show in September 2005, although demonstrations (such as Metal Gear Solid 4: Guns of the Patriots) were held at both events on software development kits and comparable personal computer hardware. Video footage based on the predicted PlayStation 3 specifications was also shown (notably a Final Fantasy VII tech demo).

What shape was the Sixaxis prototype in?