Windows

Rules

Blacken exactly two cells in each outlined 2x2 window to form one connected set of black cells which doesn't touch itself, not even diagonally. There cannot be a 2x2 square of four cells with the same colour (black or white) anywhere in the grid.

(Rules and example from WPC 2009 IB)

History of the puzzle

WPC 2009 IB lists Mehmet Murat Sevim (Turkey) as an originator of the idea.

Variants

Windows Windows

First appeared on WPC 2017/Round 4. Author of the puzzle was Prasanna Seshadri (India). This name is in a reference to previous Windows variants such as Windows Nurikabe, also by Prasanna.

Blacken exactly two cells in each outlined 2x2 window to form one connected set of black cells which doesn't touch itself, not even diagonally. There cannot be a 2x2 square of four cells with the same colour (black or white) anywhere in the grid.

Also, there are some dotted areas. Two such dotted areas forming the same shape without rotation/reflection form a ‘pair’. For cells in the same position in a pair, exactly one of the cells must be shaded and the other must be left white.

(Rules (modified) and example from WPC 2017 IB)

Appearances in the past WPCs

• WPC 2017/Round 4 (Windows Windows) by Prasanna Seshadri
• WPC 2017/Round 16 by Deb Mohanty
• WPC 2013/Part 8
• WPC 2011/Part 12
• WPC 2009/Part 2