I wanted to learn more about the HTML5 canvas when it was new, so I threw together this game over the weekend to utilize it. The game has some basic graphics, but no sprites or images were necessary; all graphics are drawn using HTML5 canvas 2D graphics methods.
The UI and game logic are completely separate, so it would be trivial to develop front ends for this game other than the HTML5 canvas version.
The source code is available at GitHub, and a HTML5 demonstration can also be found there.