Since Amit's apparently here reading, great job on updating your A* introduction (which was already excellent!), I really like how you break it down piece by piece. While it's a very simple algorithm at its core, there are some really subtle nuances that are easy to miss when you first approach it, e.g. the difference between a search node and a map coordinate (assuming classic 2D game maps).

I had some fun earlier this year implementing A* in 6502 assembler, starting with Python and working my way down through Objective-C and C before finally hand-optimizing the critical paths in asm. Articles are here for those who enjoy that kind of thing:

http://magervalp.github.io/2014/05/02/priority-queue-in-asm.... http://magervalp.github.io/2014/05/07/astar-in-asm.html

The code is available on github too: https://github.com/MagerValp/AsmAstar