Round & Revel / Error-correction deduction

Signal Salvage

Two digits changed, but the checks still remember the original.

2–6 players cooperating; no non-playing hostEstimated 20–35 minutes for three challenges; not live-playtested

Original authored print-and-play game. Time is a planning estimate; this edition has not had a live group playtest.

Good for: A number-puzzle table that enjoys explaining why a candidate cannot work.

What you need

Practice SS00 and eight received-signal cards, printed once
An eight-position answer row per challenge, pencils, and scrap paper
Separate covered solution guide; a calculator is welcome

How to play

Recover the original message

Each card shows eight received digits, read from position 1 on the left to position 8 on the right. Exactly two positions contain the wrong digit. The other six are already correct. You must identify the two damaged positions and recover the entire original sequence. Every original and received digit is 0, 1, 2, or 3. No digit has been moved, inserted, or deleted.

Trust the checksums

The card also contains six trustworthy checks. Each names several positions and gives the sum of the ORIGINAL digits at those positions. Add the digits as ordinary numbers; never concatenate them into a larger number. A check names each of its positions only once. Overlapping checks may use the same position, so changing one candidate digit can affect several sums. All six records are true, even when the received sequence fails them.

Prepare three repairs

Set SS00 aside as the worked practice. Select three different challenge cards SS01–SS08 without consulting their answers. Everyone solves the same card together. Copy a clean eight-box answer row and label the boxes 1–8. Keep the received sequence visible and unchanged as evidence. Use a second candidate row for experiments rather than erasing the original print. Choose a first analyst; continue clockwise across all three cards.

Make a useful observation

On a turn, the analyst makes one small contribution: test a printed sum, propose a possible damaged pair, rule out a candidate with a reason, or pass. The next player checks the arithmetic aloud before the discussion continues. Other players may ask questions and offer help at any time. Nobody has to calculate mentally; a calculator or written addition is welcome. Take as much time as the group needs.

Track what a check tells you

For each check, compare the received sum with its trusted sum. A mismatch proves that at least one damaged position occurs in that check. A matching sum does not prove that all those positions are correct: one digit could have risen while another fell by the same amount. Also, the two wrong digits need not change by the same amount. These possibilities are central to the repair, not exceptions to invent later.

Build a complete candidate

Choose exactly two positions to change and put a different allowed digit in each. Leave the other six received digits untouched. Test this whole candidate against all six checks, recording any failure. You may freely revise candidates and keep a list of possibilities. A proposed replacement equal to the received digit does not count as a changed position. Negative values, fractions, digits above 3, and extra changed positions are never allowed.

Submit the repair together

When you think the repair works, mark both changed positions and read the entire candidate sequence aloud. Invite each player to name a check they have verified or an unresolved concern. Submit only after every printed sum and the exactly-two-changes condition have been checked. Then uncover the matching answer. Do not open other cards’ answers. Each supplied card has one complete original sequence satisfying all its conditions.

Score the evidence, then continue

Earn 1 shared point for the correct pair of damaged positions and 1 more for the exact original eight-digit sequence. A fully correct sequence with both damaged positions correctly marked earns both points, for a maximum of 2 per card and 6 over three cards. A blank submission earns 0; an incorrect sequence does not earn the sequence point merely because a few digits match. There are no speed bonuses, penalties for discarded candidates, individual winners, or tiebreakers.

Handle printing and access

If a copied digit or checksum was wrong, restore it from the printed card and continue before submitting. If a damaged print makes the intended record uncertain, use another card rather than guess. Read position numbers distinctly from digit values, enlarge the rows, or let one person transcribe the group’s chosen candidate. All records remain visible. After scoring, the group may use the key to explain a failed inference, but it cannot revise the submitted score.

A worked example

On practice SS00, the received sequence is 2 3 2 1 3 1 0 2. Replace position 2 with 1 and position 7 with 1. The repaired sequence is 2 1 2 1 3 1 1 2. Its six sums are 5, 7, 7, 6, 8, 8, matching the printed records in order. Exactly two entries changed. Identifying both positions and this complete sequence would earn 2 points.

Printable materials

Print one copy of the cards and repair sheet, or draw a new eight-box row for each challenge. Cutting is optional. Keep answers on the separate covered guide. Do not write replacements over the received evidence.

SS00