Yajisan Kazusan

Rules

Shade some cells so that all unshaded numbered arrow clues indicate the exact number of shaded cells in the given direction. Shaded cells cannot touch each other by a side, and all white cells must form a single connected area. The numbered arrow clue cells can be shaded, and a clue once shaded may or may not be true.

(Rules (modified) from WPC 2017 IB, example by EctoPLASMA)

History of the puzzle

First appeared on Nikoli vol 74 (1998). The rules was developed together by あさおきたん (Asaokitan) & となりのトロロ (Tonari No Tororo). Surprisingly, this puzzle predates Yajilin.

Appearances in the past WPCs

• WPC 2017/Round 12 by Prasanna Seshadri