The game is indeed 64x64 ... I had just increased the display size in the index.html to 512x512 to make it easier to view/play. I have since updated it.
Don't take this the wrong way, but I remember that the tank was too linear for the resolution to be 64x64. You can indeed put the window size over 64, but the resolution has to be kept <= 64. What's the size of the tank?