This end-game puzzle is for Shithead. I am beginner, and was quite surprised this end-game seems lost to me. Is it a mathematical loss? You can treat this as a "perfect knowledge" and "perfect play" puzzle. That is, both players know what cards remain and will play optimally.
The hidden cards (2 and 5) are unknown to the players, but it would clearly be a loss if my opponent had the hidden 2, but the puzzle is if he has the hidden 5, as he did.
Player 1: One hidden card: 2. Cards in hand: 2, 44, 9999, JJJ, QQQQ, AAAA.
Player 2: One hidden card: 5. No cards in hand.
It is player 1s turn to act.
It seems to me that the fact that there are only sets (4 of a kind) left, reset cards plus 44 and 5, means I will always have to hand my opponent either 44 into his 5, or give him a reset card for the sets.