Thirteen prizes. Sealed bids.
Thirteen prize cards, 1 to 13, shuffled. One is at stake each round.
You hold bid cards 1 to 13. Each plays once. Spent, win or lose.
Both bids flip at the same moment. Higher card takes the stake.
Equal bids score nothing. The stake rides onto the next prize.
Ten seconds to seal a bid. Miss it and your lowest card plays for you.