The visualizations and explanations are fantastic. The mouseover highlighting of code as you mouse over the hexes in the 'Neighbors' section remind me of Bret Victor's work[1]
Also, I was amused to see that the author used a language called "Haxe"[2] which can generate (compiles into) javascript, flash, C++, java, C# etc. I guess it's good for making web games where you have a flash fallback (or vice versa)?
[2] http://haxe.org/