Book Mastery
How to Play & Scoring Rules
Fill every row, column and 3×3 box with the digits 1–9 exactly once. Every puzzle has a single solution.
Controls: arrows move, 1–9 place, Backspace erases, N toggles notes, Ctrl/Cmd+Z undoes.
Scoring: your time plus +10s per mistake and +15s per hint is compared to par. Beat par to gain rating; slower solves gain less or lose. Three mistakes ends the run (−12).
Accuracy is correct placements ÷ all placements. Gaps over 45s count as hesitations.
Strategy Tips
- Naked singles: a cell with only one possible candidate.
- Hidden singles: a digit that fits only one cell in a row, column or box.
- Pointing pairs: candidates locked in one line of a box eliminate that digit elsewhere on the line.
- Naked pairs: two cells sharing the same two candidates clear them from the rest of the unit.
- Scan digits with the most placements first — they're the easiest to finish.