Ninefold Sudoku

▦Ninefold Sudoku

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Your ingredients

Classic Sudoku is always the foundation.
Add any combination below.

∑Killer cagesSmall groups with a given sum.
No digit repeats inside a cage. ♞Anti-knightEqual digits cannot be a chess
knight’s move apart. ╳DiagonalsBoth long diagonals also
contain 1–9 exactly once. ↗ThermometersDigits increase strictly from
the round bulb to the tip. ➶ArrowsCircle equals the sum along
its arrow. Repeats allowed. ◦●Kropki dotsWhite: difference 1. Black: 1:2.
No rule on unmarked edges. AEqual lettersMatching letters share a digit.
Different letters may match. ♚Anti-kingEqual digits cannot touch,
including diagonally. ♛Queen (9s)No two 9s share a diagonal.
Other digits are unaffected. 〰German WhispersGreen-line neighbours differ
by at least 5. ∿RenbanPink lines contain consecutive
distinct digits, in any order. ＝Region-sum linesBlue-line box segments
have equal sums. ≠Non-consecutiveCells sharing an edge never
hold consecutive digits. XVXVV: sum 5. X: sum 10.
No rule on unmarked edges. ↔PalindromesOrange lines read the same
from both ends. ⊕ZippersTeal lines: cells equally far from
the middle sum to the middle cell. ◴QuadruplesDigits in a corner circle appear
in the four cells around it. ΣXX-sumsOutside number: the sum of the first X digits
from that side, X being the first digit. ☁Fog of warCells start dark. A correct digit lights its cell and
the eight around it. Clues show only in lit cells.

DIFFICULTY

Pick a difficulty and Ninefold looks for a puzzle of that label in your rules, trying a few clue styles and seeds. It can take a little longer.

CLUE STYLE

New puzzles automatically seek a discovery trail, comparing three constructions for useful follow-through, varied reasoning, and fewer repetitive stretches.

SEED

A fresh construction, with a checked logical solve.

Your plays

App & storage

Preparing puzzles and the local generator for offline play…

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Progress stays in this browser. Backups let you move it to another device.

0:000 mistakes found0 hints0 undos

YOUR NEXT PUZZLE

Killer Sudoku

Standard Sudoku rules also apply: each row, column, and 3×3 box contains 1–9 exactly once.

✦PUZZLE COMPLETE

You did it!

Ideas in this puzzle

These ideas appear in the puzzle’s checked solve path. You may have found a different route.

Your next challenge

Take your time.

The clock is paused.

Finding a good puzzle…Checking its solution and its deductions on this device.

MeaningColor

Toggle colors independently: choose both Odd and Even to record either possibility. All palettes stay visible; hint colors are separate. Colors never change candidates.

Select a cell, then type 1–9.

Try the idea

Try an answer, or continue to the reasoning. This does not change your grid or count as a mistake.

A useful approach from current entries and checked candidates; not a claim of the best or only solve path. Manual pencil marks and colors are not treated as proof.

Can the selected cell be

Learn to use colors

COLORING APPROACH

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Install Ninefold Sudoku

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Open this site in its own browser tab if you are viewing an embedded preview. Wait for “ready offline” under App & storage before disconnecting. Puzzles, hints, and custom generation then run on your device.