25×25 nonograms

Twenty-five squares a side is the marathon: 625 squares and a picture with real detail. Pick a difficulty and start.

What changes at 25×25

A 25×25 board is rarely a one-sitting puzzle, and it doesn't have to be. Autosave keeps your progress in this browser, so you can leave and come back.

The board is five blocks of five in each direction. Treat each 5×5 block along the guides as a small puzzle of its own, and the size stops feeling endless.

Techniques that matter. There are fifty lines and 625 squares, so one missed deduction can sit unnoticed for a long time. When a region of the board stops making sense, stop and look for the wrong square before you build more on top of it. By default it is marked as soon as you place it; with "Only when I press Check" chosen in Settings, Check counts the wrong squares for you. A wrong fill found early costs one undo; found late, it can cost a whole block. Autosave means you can do this at your own pace.

Tips for 25×25

1. Work in 5×5 blocks. Settle one block between the guides before you move to the next.
2. Keep crossing. On a 25-wide line, crosses are what turn one long problem into several short ones.
3. Take breaks. Fresh eyes spot the line you missed; your board will be waiting.

Expert boards can't be finished with line-by-line reasoning alone. You'll need lookahead (see How to play).