URL Hunter is Probably Interactive’s example of HTML5 elements being used to manipulate strings in the browser address bar. In this case, to play a game.

URL Hunter!
An experimental game using the URL bar as the game screen.
How to play?
Look up at the url bar! You are the O! You are trying to kill the a’s. Use the Left and Right keys to move. When you are over an a press spacebar to kill it!