Very good!
Runs smooth on IE 7 Vista for me.
The visuals remind me of TonyPa shoot series.
Did you used the Bitmap Drawing API from bytearray ( http://www.bytearray.org/?p=67 ) ?
I loved the way you ask the username at the begining of the game.
Btw, when I click on the "scores" button, I get a javascript error on the page and nothing happens.