Might also be nice to have a 'Start Game' button--I clicked the link and then got a dialog about losing. Blocks on the edges are also a little hard to get at. Nice job! Fun too. :)
Perhaps some instructions would help. I'm on a pad and lost 4 times in a row with no idea what I'm supposed to do. Tapping the "field of play" seems to have no effect.
You should also use requestAnimationFrame instead of setInterval.