A few months ago, I wrote that I was working on interactive illustrations for my A* pages. Has it taken that long? Well, I've actually had things working for a while now. I just haven't published it. Why? It turns out that my A* pages, which I wrote a long time ago, are really out of date. As I was trying to illustrate various concepts, I was trying to illustrate the concepts from my pages, but not all of them worked well in my Flash program. I eventually realized that some of those concepts are just unimportant in practice. I also discovered that the style I used in my diagrams only works for very simple maps. Once you add terrain into the maps, the visual style fails to convey the concepts I wanted to illustrate.
I haven't yet resolved these issues, which are taking a lot more time than writing the code itself. The algorithm and data structure code is complete, so I've uploaded them to my web site. You can see source code and the applet running on a square grid. The code is released under the MIT license; feel free to use it. I made the A* portion work on any graph, and included square, hexagonal, and triangular grids. This isn't the most efficient approach, but I wanted something flexible so that I could later use it in my article on grids. I haven't finished the hexagonal grid code yet; the only thing missing is the pixel coordinate to hex coordinate transformation. Enjoy!
Once I figure out the best way to display the important concepts for A*, I'll update my A* pages to use the interactive diagrams.