Invented by Nikoli, Mochikoro is celebrated for its dual requirements: every white island must be a mathematically perfect rectangle, yet all islands must be linked through diagonal contact points.

Core Principles

• The 1-Clue Area Match: A white rectangle can contain at most one circle clue. If it has a clue, its total width \(\times\) height must equal that number.
• Diagonal Network Unity: No isolated archipelago. Every island must touch at least one other island at a diagonal corner.
• No \(2\times 2\) Black Voids: You can never allow a \(2\times 2\) block of black squares to form. If three cells in a square are shaded, the fourth must remain white!

Tactical Tips

Clues of size 1 are the easiest starting anchor: they can never expand in any direction, so all four of their orthogonal neighbors are immediately black! For clues of size 2, remember that a \(1\times 2\) or \(2\times 1\) island requires black walls surrounding its perimeter. Use the Dot mode to mark cells that must be white to prevent \(2\times 2\) black voids.