It´s a great start. I tried it in Chrome and it worked OK, however the mouse cursor didn´t look right most of the time and wasn´t centered. The speed and feel of the freehand tool is surprisingly good. Keep that code if you can.
If it one day supports zoom, palette modification, lines, boxes, (basic) fill and ellipses you should show it to a broader audience. They will love it.
Oh, and can you load and save to/from local storage?
