Divide the grid into L-shaped regions. Regions can contain zero, one or more clues among circles and arrows. A circle must always be in the cell where the region containing it turns and an arrow must always be at an end of the region containing it, pointing inwards. Some circles contain numbers, that show the size of the region they are contained in.
(Rules and example from WPC 2017 IB)
History of the puzzle
First appeared on Nikoli volume 134 (2011). Sashigane means "carpenter's square" (an L-shaped tool) in Japanese.
Appearances in the past WPCs
- WPC 2017/Round 16 by Ashish Kumar