Sry if I repeat what has already been commented. The visuals are really great. The intro before the game started seemed strange. I thought maybe the game had already started because it reacted to the mouse and I thought that maybe I should do something with these tiles to proceed. A text like "press any key to skip" and the ability to skip could help.
It would be also nice to upscale the game to maximum browser area. Have you tried letterbox scaling?