That is amazing. Thanks for posting this puzzle!

It took me a while to fully understand the puzzle, but finally I fugured out that the only way white can win this game is by doing those exact moves. Nothing else will work.

why can't you do 12.e8=Q?

Because then black can force a stalemate. See if you can figure out how.

white wins lol 

That was awesome! Thanks for posting! :)

amazing puzzle

What a great puzzle, very complex yet logical so anyone could solve it if they think it through. Thanks for posting this!!

Yes, this puzzle is my favorite.  As proof that it's my favorite, 15 years ago, in 1997, I devoted an entire page to on my website:

http://www.edcollins.com/chess/under-promote.htm