Every cell announces how many neighboring cells have the opposite parity. Learn to inspect one neighborhood, propagate a change, repair contradictions, and build a complete grid whose clues all agree at once.
Your goal: build a complete grid in which every positive number correctly counts its neighbors of the opposite parity. Odd means 1, 3, 5, …; even means 2, 4, 6, …. Count neighbors sharing a side or a corner, but never count the cell itself.
There can be more than one valid grid. Success means every clue in your completed grid agrees, not that it matches the first example shown.
Every filled cell must contain a positive whole number; zero is not permitted. A cell never counts itself. An even cell counts neighboring odd cells. An odd cell counts neighboring even cells. “Adjacent” includes sharing a side or sharing a corner.
Number mode: choose a cell and enter its actual number. The checker tests it against its neighbors.
Parity mode: choose whether a cell is intended to be odd or even. The computer writes the number required by its neighbors. That number must agree with your choice.
The selected cell is gold. Every cell sharing a side or a vertex is highlighted.
Click a neighboring square to switch it between odd and even.
Only some entries are shown in the printed illustration. Blank cells mean not shown, not zero; this mission counts only the shown opposite-parity neighbors, not a verified full filling. Click either circled clue. Gold cells are its known opposite-parity neighbors.
Click any cell. Its neighbors are outlined, and opposite-parity neighbors are gold.
The worked example grid has been changed in exactly one place. Select a cell, then choose a replacement number.
Click a cell to flip its intended parity. The number shown is the opposite-parity neighbor count forced by that pattern.