About Killer Sudoku
Killer Sudoku on the unleaded windows of a glaziers' loft at dusk: every cage is a pane of coloured glass held by lead, the boxes are fenced by iron saddle bars, and a pane whose numbers add up catches the evening sun.
Fill the window so every row, column and box holds each number once. There are no printed numbers: the figure in each pane's corner is what its numbers add up to, and no number repeats inside a pane.
All 140 windows are open from the first visit, across five kinds from the 6×6 Lancet to the 9×9 Rose. Every one is proved to have exactly one answer by an independent count and to be solvable by reasoning with no guess; the kinds are set by the reasoning they need, from pane combinations to the rule of 45 across several rows.
Each window keeps a named fastest first solve and a public top ten. The window cards and the live clock both print the record and who holds it.
How to play
- Goal
- Fill the window so every row, column and box holds each number once and every pane adds up to its figure.
- How it ends
- A window is solved when every cell is painted by those rules. There is no way to lose.
- Record
- The fastest first solve of each window, with its holder's name.
- Tap a cell, then a number: every row, column and box holds 1 to 9 once (1 to 6 in a Lancet).
- Each pane's numbers add up to the figure in its corner, and no number repeats inside a pane.
- Switch to Notes to write candidates; a painted number wipes itself from the notes in its row, column and box.
Controls
| Tap / click | Select a cell |
|---|---|
| Number pad / 1–9 | Paint a number (again to take it out) |
| Notes / Shift+number | Write a note |
| N / P | Notes mode, paint mode |
| Delete / 0 | Clear the cell |
| Z / Escape | Undo, or return to the windows |
All 140 windows are open, deterministic, proved to need no guess and independently counted to one answer. There is no hint and no answer check: the page ships no solver and no answers, only what you can see (a number twice in a row, column, box or pane, and a full pane that misses). Named fastest times, kept attempts, notes, sound and reduced-motion preference persist in this browser.
