The Kakuro book said “Expert.” You believed it for the first ten minutes, while the corners filled in nicely. Now you’re looking at a block in the middle of the grid where every clue has five ways to be right, your pencil marks are three deep, and the eraser has worn a soft gray …

You’ve hit a wall in an expert Kakuro. Every magic block on the page is filled in, every easy crossing is done, and a fat block of empty cells is sitting in the middle of the grid. Each clue around it has five or six workable combinations. You pencil a few, erase them, and pencil them again. …