Hidden trap bid
Choose between adding a hidden card and committing to a risky reveal count.
Cooperation & communication
- Players
- 3–5 players
- Time
- 15–20 minutes
- Materials
- Four cards per player: three safe circles and one trap cross; score sheet.
Prepare
Each player privately holds three circles and one cross. The starting player rotates each round. Everyone first places one chosen card face down in their own stack. On each subsequent turn either add one card on top of your stack or start a bid from 1 up to the total cards currently on the table.
Play
Once bidding starts no more cards are added. In order, raise the current bid by at least 1, without exceeding the table total, or pass for the round. When all but one pass, the last bidder must reveal the promised number. A bidder may immediately win the bidding if their bid equals the whole table total.
Worked example
Reveal every card of your own stack first, top-down, then choose an opponent’s top card at a time. You cannot choose a buried card. Stop at the first cross and lose 1 point. If the promised count is reached with circles only, gain 1. Everyone else’s score stays unchanged.
Finish and check
If your own stack has three cards but your winning bid was 2, you still have to reveal all three own cards; therefore such a bid cannot be legally started or raised by you unless it is at least your own stack size. Play six rounds, returning all cards each time. Highest score wins; ties share victory.
Adaptation and limits
Keep scores as integers, including negatives; no money or elimination. Check the total table count publicly before bids. A later player may pass rather than exceed a safe plan. Small opaque paper cards work, but use identical backs so trap marks cannot be seen.
Purpose, observation and provenance
Within this activity: Choose between adding a hidden card and committing to a risky reveal count.
Confirm the bidder reveals all their own cards first and reads stacks top-down.
Our rules, examples and printable diagrams are separately prepared. The earliest inventor of the broader mechanism is not established here.
Free alternative: Copy the supplied grids, labels and cards onto reused paper. No specialist product is needed. Adults may prepare pieces or act as a scribe.
Printable materials
Preview at 100% scale, with browser headers and footers off. Cut with suitable help. Keep host keys separate. This is a manual tabletop kit, not an online opponent, automatic judge or solver.
Player materials · Hidden trap bid
Each player: ○ ○ ○ ×, identical backs.
Round 1–6 / starting player / own-stack size / bid / success / score.
Cards / pieces · prepare before play
Player 1
Player 2
Player 3
Player 4
Player 5
Player record · keep the host key separate
| Round | Bid | Result | Score |
|---|---|---|---|
| ________ | ________ | ________ | ________ |
| ________ | ________ | ________ | ________ |
| ________ | ________ | ________ | ________ |
| ________ | ________ | ________ | ________ |
| ________ | ________ | ________ | ________ |
| ________ | ________ | ________ | ________ |
| ________ | ________ | ________ | ________ |
| ________ | ________ | ________ | ________ |
Host key · separate from players
Own-stack size is a bid lower bound; reveal own whole stack first, then opponents’ top cards.
Run the round
Each player privately holds three circles and one cross. The starting player rotates each round. Everyone first places one chosen card face down in their own stack. On each subsequent turn either add one card on top of your stack or start a bid from 1 up to the total cards currently on the table.
Once bidding starts no more cards are added. In order, raise the current bid by at least 1, without exceeding the table total, or pass for the round. When all but one pass, the last bidder must reveal the promised number. A bidder may immediately win the bidding if their bid equals the whole table total.
Reveal every card of your own stack first, top-down, then choose an opponent’s top card at a time. You cannot choose a buried card. Stop at the first cross and lose 1 point. If the promised count is reached with circles only, gain 1. Everyone else’s score stays unchanged.
If your own stack has three cards but your winning bid was 2, you still have to reveal all three own cards; therefore such a bid cannot be legally started or raised by you unless it is at least your own stack size. Play six rounds, returning all cards each time. Highest score wins; ties share victory.
Keep scores as integers, including negatives; no money or elimination. Check the total table count publicly before bids. A later player may pass rather than exceed a safe plan. Small opaque paper cards work, but use identical backs so trap marks cannot be seen.
Related activities
Activity library · Hidden dice count calls: rules and printable materials