I will post my full notes on this puzzle in a few days, but for those interested, I gave this puzzle to Alena on October 2nd, and her solution is spread out over 3 threads in the following week or so after that.

I solved this puzzle a couple of weeks after you gave it to me, Cortex, but I don't remember if I actually posted it in the old thread at the time- I do remember posting the solution up to about move 17 or so in the line. I actually gave this puzzle to Alena a couple of months ago, and she eventually solved it after I gave her a few hints along the way. This is actually the most difficult puzzle I have actually solved.