It looks like Mozilla has finally started to enter the HTML5 game, literally. Runfield is a simple yet wacky HTML5 game demo in which you take the role of a hyper fox. Simply click to jump over the holes and ditches. Mozilla sponsored the game as part of their Web O’(open) Wonder promotion to show off the power of Firefox 4. The website contains a bunch of HTML5 demos and goodies to play around with.