Draw lines from the @ symbols to the black and white circles, so that each @ is connected to one black and one white circle, and each circle is used exactly once. The lines run horizontally and vertically, and each empty cell is used by exactly one line. If a circle contains a number, that number indicates how often the line from the respective @ symbol to this circle makes a turn. In circles with a question mark the number of turns is unknown.
History of the puzzle
Possibly German origin. According to janko.at, this puzzle was present in first two volumes of LOGISCH magazine in Germany, published in 2005.
Appearances in the past WPCs
- WPC 2019/World Cup Round 2 by Jürgen Blume-Nienhaus