The Guardian – Alex Bellos
“The author of today’s puzzle is Loïs B, a 12-year-old boy from Luxembourg, who said he got the idea when reading a puzzle book during his science class. Bravo Loïs! I’m not sure many 12-year-olds would be able to solve this puzzle, let alone create one like this. (I have taken the liberty of adapting his puzzle with a festive theme.)” (more)