Pencil Marks & Notation

Easy puzzles never need notes: every step is a scan, and the board itself is the notation. The moment a puzzle stops handing you singles, though, progress comes from eliminations — and eliminations only exist as marks. A technique like a naked pair doesn't place a digit; it removes candidates, and something has to record that.

Notes are not a crutch. Every technique beyond the basics is defined in terms of candidates, so the pencil marks are the playing field itself.

The complete inventory: every cell lists every digit its row, column and box still allow. This is the notation the technique catalog assumes — subsets, fish, wings and chains are all patterns in the candidate layer.

Maintaining it by hand is honest work but slow, and a single forgotten mark can hide a pattern or fake one. That's what auto candidates mode is for: the board keeps the inventory current while you strike out candidates your own deductions remove. On paper, most solvers only switch to full notation when the puzzle demands it.

Named after speed-solving champion Thomas Snyder: only write a candidate when a digit has exactly two possible cells left in a box — and write nothing else. The result is a board carrying only strong information: every mark you see is one half of a strong link.

Snyder notation is fast because it ignores almost everything, and powerful because what it keeps is exactly what cracks most hard-but-fair puzzles: box-based singles, pointing pairs, and the skeleton of X-Wings, Skyscrapers, Kites and Cranes. When the pair marks stop producing moves, upgrade the board to full notation and continue with the heavier techniques.

There's no prize for the fanciest notation — use the lightest one that keeps you moving: