Oh goodness, haha. Doing this project I've learned that there is a great deal of variety in handwriting style. Single-stroke vs. Multi-stroke 5 for example, seems to be a big point of contention. I'll extend the decision tree to be more friendly about bottom-starting strokes.
This is a great point. When I first implemented the visualization, I actually used a circle until someone pointed out to me that the formula describes a square region around the datapoint and not a circle. I think you are very right in saying that this decision was made by Groner solely for efficiencies' sake in 1966. I'll probably add a side-note to explain this a bit.
I'll take some time tonight to make it a bit better at dealing with different shapes of Bs. If you want to know what the 'canonical' stroke pattern is, you can click on the little graphics above the tablet. They will animate to show you the expected stroke path (although, it should just work, so I'll fix that tonight)
Wow, that really means a lot. Thank you! Really glad to hear that you are finding it useful. Please send along your feedback and questions if anything doesn't make sense or is poorly communicated in the text/visualizations.
Yeah, the situation is still pretty grim. I spent a good half week trying to get canvases scaling while maintaining chunky pixels across multiple browsers and finally gave up. In Goya, all of the pixels are drawn as rects. I actually read your 'drawing pixels is hard' article two or three times while I was trying to track down a good solution.
<input type="color">
This is just a little weekend project, and I wanted to use as much standard stuff as possible. I believe the color input type is coming to firefox soon though.