There are 15 stairs arranged in a line. There are 6 people on various different steps.
The only rule is you can only move a person if you move it to any lower vacant stair.
In a two player game, you alternate moving single people. The last one to move a person wins! What strategy should you use in order to win?
What strategy would be used if the people couldn't pass each other when moving down the stairs?
(In reply to re: Half the answer
WRONG! It's nim, but with alternate gaps! The nim-heaps are: the gap between the lowest person and the bottom, the gap between the 2nd and 3rd lowest person, etc. And if one of those gaps is increased, you can ALWAYS move it to decrease it back towards where it was, making it a reversible move.