Six puzzles. One chain. Solve them out of order, and you can't finish.
SuDOMIno is six standard 9×9 sudoku grids that must be solved in sequence — each one depends on numbers you copy in from the one before it. Grids 2 through 6 aren't just hard, they're mathematically incomplete on their own: there's no guessing your way past them, and no skipping ahead.
Every other sudoku collection is a set of independent puzzles you can solve in any order. In SuDOMIno, grids 2 through 6 are printed with too few clues to have a unique solution on their own — a mathematical fact, not a difficulty rating.
Each grid holds back just enough clues that it can't stand alone. Solve one, copy a few marked numbers into the next, and the chain keeps moving. Skip ahead, and you're stuck — there's nothing to guess at.
Every set follows the same four-step rhythm, six times over.
A normal, complete, standalone 9×9 sudoku — nothing unusual yet.
A few highlighted cells in the grid you just finished get copied into the matching marked cells on the next grid — same position, grid to grid.
Every chained grid includes a checksum hint ("these should sum to 42") so you can catch a copying mistake before you start solving.
Solve the next grid using its printed clues plus your copied numbers. Repeat through Grid 6 — an answer key is included if you get stuck.
Every puzzle is checked to make sure it can be solved through logic alone — no guessing required.
Solvable with straightforward, single-candidate logic throughout.
Adds a bit more pattern-spotting — paired candidates, box/line logic.
Requires holding more of the grid in your head at once — and leans more heavily on the numbers carried over from the previous grid.
Two sets per difficulty, plus two Mixed sets that ramp from easy to hard across the chain. Each download is a full 6-grid set with answer key.
No — grids 2 through 6 are unsolvable on their own by design, provably, not just "harder." The chain isn't decorative; it's required.
Every chained grid has a checksum hint so you can verify your copied numbers add up correctly before you start solving — catching transcription errors early.
A full answer key is included at the back of every set.
No — sets are available in Easy, Medium, and Hard, and even the hardest tier is solvable through logic alone, never guessing.