Even/Odd Fence
Even/Odd Fence was introduced at the World Puzzle Championship 2010 in Poland (author unknown) under the name Even/Odd Slitherlink.
This variation removes the usual numeric clues of Slitherlink and replaces them with a simple parity condition: each cell is marked as even or odd, and the loop must pass along the edges of that cell an even or odd number of times accordingly.
Although no explicit numbers appear in the grid, the puzzle remains surprisingly solvable. The parity constraints interact in subtle ways, producing rich logic that feels both familiar to Slitherlink solvers and refreshingly new. The result is a clean, elegant puzzle type that relies on structural reasoning and parity propagation rather than traditional counting.
This variation removes the usual numeric clues of Slitherlink and replaces them with a simple parity condition: each cell is marked as even or odd, and the loop must pass along the edges of that cell an even or odd number of times accordingly.
Although no explicit numbers appear in the grid, the puzzle remains surprisingly solvable. The parity constraints interact in subtle ways, producing rich logic that feels both familiar to Slitherlink solvers and refreshingly new. The result is a clean, elegant puzzle type that relies on structural reasoning and parity propagation rather than traditional counting.
Rules
Draw a single continuous loop along the gridlines in the diagram. If a cell is shaded, then even number (0, 2 or 4) of the cell's edges are used by the path. If a cell is not shaded, then odd number (1 or 3) of the cell's edges are used by the path. The path cannot cross or touch itself.
Click to see the answer.