Pretty cool, though like others I had some slight technical issues. On Firefox mobile I got a black screen (that was yesterday, maybe it's been updated since then). Firefox desktop today it worked once I figured out that:

a) the keyboard doesn't work until after I click to fire, and this state resets itself every time I press f5 to restart the game (presumably a browser focus issue)

b) both up/down and w/s work for back and forward, but a and d don't work for left and right, you need to use the left/right arrows.

The combination of the two had me scratching my head for a little while!