Poison corner grid: rules and printable materials

Remove a chosen cell and all remaining cells above and to its right; avoid the marked corner.

Players

2

Plan for

8–15 minutes

Bring

Seven-column four-row grid and pencil

Mark the protected corner

Use four rows numbered 1 at the bottom through 4 at the top, and columns A–G left to right. Cell A1 is marked P. It is an ordinary remaining cell except that choosing it loses immediately. All 28 cells start present. No food is used or eaten; the board is a paper strategy game.

Remove an upper-right rectangle

Choose any present cell. Cross out it and every still-present cell whose row is at least that row and whose column is at least that column. In other words, take the rectangle toward the top-right, including the chosen corner. Previously removed cells simply remain removed. A move must remove at least its chosen present cell.

Worked move

Choose D2 from the full board: rows 2–4 in columns D–G are removed, twelve cells total. A1 remains. Next choosing F1 removes F1 and G1; higher F/G cells were already absent. Choosing a removed cell is not allowed, and you cannot choose a bottom-left rectangle instead. The printed coordinates prevent “above” from changing when players sit opposite each other.

End on the protected cell

Players alternate. Whoever chooses A1 loses immediately; do not remove the mark to continue. When A1 is the only remaining cell, the player whose turn it is must choose it and loses. You cannot pass. For a two-round friendly match, use fresh boards and exchange the starting player, sharing the match if each wins once.

Make moves clear

Before crossing out, announce the coordinate and point toward the printed top-right arrow. A helper may mark the chosen rectangle. Keep removed cells visibly crossed rather than cutting loose pieces. The sheet provides two boards for practice and play; it is not a solver and does not promise the starting player a particular strategy.

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.