2026-07-28 · history
Yajilin (1999) — A Board Where Two Rule-Systems Were Grafted Together
In July 1999, Puzzle Communication Nikoli issue #86 introduced Yajilin, a hybrid pencil puzzle that grafted the "draw exactly one loop" grammar established by 1989's Slitherlink onto a black-cell-counting rule. It reused the arrow-and-number cell from a puzzle published just before it, Yajisan-Kazusan, and by 2005 had already been adopted, as "Arrow Ring," into the US qualifying round of the World Puzzle Championship. From official Xbox and PS Vita ports to a dedicated 2025 mobile app called Loopr, we trace, with sources, 26 years of this grid's survival.
