In a “haunted square,” every cell contains a ghost, pumpkin or vampire. As in Sudoku, each row and column must contain only one of each creature type, as shown in the example grid.
Numbers placed around the edge of the square indicate how many creatures are visible from the corresponding row or column. Solving the puzzle requires taking the creatures’ different sizes into account: ghosts are larger than vampires, which are larger than pumpkins. A creature hidden behind a larger one cannot be seen.
There is one exception. Because ghosts are transparent, pumpkins can be seen through them. Vampires, however, cannot be seen through a ghost.
In the example, the number 2 beside the first row means that the ghost in the foreground and the pumpkin visible through it can be seen, while the vampire is hidden. The 2 beside the second column indicates that the vampire and ghost are visible, but the pumpkin is concealed by the vampire.
The puzzle challenges readers to use the clues to place the three creatures in the cells of grids A and B. The continuation of the article, including the full puzzle, is reserved for subscribers.
Sources: Le Monde Sciences.