50 medium nonograms for when lines stall.

The first half of a medium puzzle looks like an easy one. Clues at the edges give you long certain runs, the picture starts to show, and then it stops. No single row or column tells you anything more on its own, so the way forward is to hold a placement in your head, follow what it forces, and keep it or discard it. One careful branch settles these puzzles, and you are never asked to gamble.

Every grid was machine-checked for a unique solution before it went in the book, so a contradiction you find is real information rather than a flaw in the puzzle. The solutions are symmetrical geometric patterns, which gives you a second check: if a half looks lopsided, something upstream is wrong.

The tablet editions run to 105 pages with two-way links, from the index to a puzzle, from a puzzle to its answer, and from the answer back again. The print editions lay each grid out to the sheet so no clue column is cropped, and the answer key sits at the back.