The Poisoned Position
This video presents the same text shown beside it, spoken and on screen. It adds nothing the text does not say.
State
In a solved game some positions are lost for the player to move: every available action hands the opponent a winning position.
Show
Pebbles with three left — take one or take two, the opponent inherits a win either way.
Watch for
Lost does not mean badly played; from a poisoned position, best play loses more slowly, not differently.