Double Back

The Double Back puzzle first appeared in 2009 on Palmer Mebane’s (USA) puzzle blog Melon’s Puzzles, where it was introduced as an original creation blending elements of region-based path puzzles and logical deduction. Mebane, a prominent figure in the logic-puzzle community and a frequent contributor to the World Puzzle Championships, designed Double Back to explore the idea of a single loop that must traverse each region exactly twice—a deceptively simple rule that allows for deep logical interplay between local and global constraints. Following its publication on Melon’s Puzzles, the format quickly gained popularity among online puzzle solvers and was later adopted in various independent puzzle contests and community sites such as Logic Masters India and Puzzle-Up. Over the years, numerous variations and refinements have been introduced, solidifying Double Back as a modern classic in the world of region-loop logic puzzles.