15×15 Nonogram Puzzles

Fifteen is the size this catalog is built around. This bucket holds close to half of everything on the site, and it is the point where a nonogram stops being a warm-up and starts being a puzzle you sit down with. A 15×15 board holds 225 cells against the 100 of a 10×10, so there is more than twice as much to work out, and the pictures have room for internal detail rather than just a recognisable outline.

There is one piece of arithmetic worth internalising before you start, because it explains why this size feels so different from the one below it. A clue of length k in a line of n cells forces 2k − n cells to be filled, no matter where the block finally sits. On a ten-cell line, a clue of 8 hands you six cells for free. Stretch that same line to fifteen and the same clue of 8 gives you exactly one. Overlap alone carries you a long way through a 10×10; at 15×15 it opens the board and then leaves you to do the real work by cross-referencing rows against columns.

Not every board here is square. Most are true 15×15, but eight are 10×15, seven are 15×10, and one outlier is 5×15 — three times longer than it is wide. That distinction matters more than it looks. In the 10×15 boards the rows are ten cells long while the columns are fifteen, so the row clues are the ones that pay out first; in the 15×10 boards it is exactly the other way round. Asking which axis is shorter before you place a single mark is worth more on these than any individual technique, and this bucket has enough rectangular boards to make the habit stick.

A substantial minority of the bucket is rated hard, but they are not spread evenly across the themes, and knowing where they cluster lets you pick your difficulty without guessing. Food & drink is the steep end, with most of its boards at this size rated hard. Zodiac signs is steeper still in proportion — eight of twelve — because every sign in that set is drawn at exactly 15×15, so the size tells you nothing about how much deduction a given one will take. At the other end, the everyday objects and alchemy boards at 15×15 sit almost entirely at normal.

So a sensible route through this size is to start with everyday objects or alchemy, where the pictures are built from straight edges and isolated symbols and the ratings stay gentle, then move to animals or board games, and leave food & drink and the zodiac until the cross-referencing feels automatic. Board games is worth a special mention here: most of its boards are at this size, and most of those are dice, dominoes and chess pieces, and those subjects produce clue numbers that behave predictably — a good place to watch a technique work cleanly before applying it to something organic.

If 15×15 is still a stretch, the 10×10 bucket is the shorter version of the same problem and a better place to learn the overlap rule while it still does most of the work for you. If it has stopped being a stretch, 20×20 is where these techniques become mandatory rather than merely useful: 400 cells, and no way through by inspection.