I tried it out, using IE (I know most people use other browsers, but you should always try to be a cross browser compatible as possible)
There are only a few little things that I noticed
1) When loading the resources, after pressing the 'Play' button, it sort of just 'hangs' , at first I thought my window locked up, but then the game started, so, maybe a 'loading' screen or progress bar would help to show that it didnt just lock
2) The screen will scroll smooth most of the time with the player, but on occasion the screen will shake, almost like there is an earthquake happening. Not sure if you are doing that on purpose?!?! If you are... cool, but if not, might want to check out your screen movement (camera movement) code.
I really think you have a cool idea, and I see lots of potential here. Good job XD