Inturnal
Inturnal is a loop-drawing puzzle type first introduced by Alan Fetters for the World Puzzle Championship 2023.
Although the puzzle visually resembles Slitherlink, its logic is fundamentally different. Instead of counting the number of edges of the loop around a cell, each clue indicates how many of that cell’s four corners lie inside the loop. This inside/outside relationship forces the solver to reason globally about the loop’s shape and orientation, rather than locally counting edges.
Because of this unusual clue mechanism, Inturnal requires a distinctive style of deduction. Solvers must track the loop’s curvature and interior/exterior regions, often thinking several steps ahead. The result is a puzzle that looks familiar but plays in a completely fresh and innovative way.
Although the puzzle visually resembles Slitherlink, its logic is fundamentally different. Instead of counting the number of edges of the loop around a cell, each clue indicates how many of that cell’s four corners lie inside the loop. This inside/outside relationship forces the solver to reason globally about the loop’s shape and orientation, rather than locally counting edges.
Because of this unusual clue mechanism, Inturnal requires a distinctive style of deduction. Solvers must track the loop’s curvature and interior/exterior regions, often thinking several steps ahead. The result is a puzzle that looks familiar but plays in a completely fresh and innovative way.
Rules
Draw a single, non-intersecting loop that only consists of horizontal and vertical segments. Numbers inside a cell indicate the number of quadrants of that cell that are inside the loop.
Click to see the answer.