How to Play

Mini Sudoku is a sudoku shrunk to six digits. The grid is six squares across and six down, cut into six boxes that are two rows tall and three columns wide. Every row, every column and every box has to end up holding each of the digits 1 to 6 exactly once — no digit twice in the same row, column or box.

Tap a square to pick it, then tap a digit to write it in. Tapping the same digit again rubs it out. The digits that came with the board are fixed and will not budge. On a keyboard, the arrow keys move the selection, 1 to 6 write a digit, and Backspace clears the square.

Every board is proved to have exactly one answer before it is handed to you, so there is never a point where the only way forward is a guess. If you are stuck, the deduction you need is on the board somewhere.

Turn Notes on and the digits you tap are pencilled into the corner of the square instead of filling it. That is how you keep track of a square that could be a 2 or a 5 without committing to either. Turn Notes off again to write a real answer. Two conveniences save the usual bookkeeping: writing a digit wipes that square’s own notes, and it also rubs that digit out of the notes of every square that can no longer take it — the rest of its row, its column and its box. You will never sit staring at a pencil mark that stopped being possible ten moves ago.

Tips for Harder Boards

• Count the crowded digit first. Whichever digit already appears most on the board is the one with the fewest places left to hide. The pad shows how many of each are still missing, so you can pick your target without counting by eye.
• Read boxes, not squares. A box is two rows and three columns, so a single digit placed elsewhere in those rows often rules out most of it at once. Asking “where can the 4 go in this box?” beats asking “what can go in this square?” far more often on a 6 × 6 than it does on a full-size grid.
• Use the highlight. Selecting a square lights its whole row, column and box, and every other copy of the digit it holds. Tap a square you have already filled and the board shows you, in one glance, everywhere that digit cannot go.
• Pencil the pairs. Two squares in one unit that can only take the same two digits lock those digits out of everything else in that unit. On a six-digit board that single observation often finishes a box outright.
• When nothing jumps out, change the question. The boards that stall you are the ones where no square has a single obvious answer. That is the moment to stop asking what fits a square and start asking where a digit can live in a unit — it is the technique the hardest stages are built around.

A Hundred Stages, Each One New

The ladder runs to 100 stages. The first six are 4 × 4 warm-ups with 2 × 2 boxes and digits 1 to 4 — enough to learn the controls in under a minute. Everything after that is the full 6 × 6 board, with fewer starting clues and longer chains of reasoning the higher you climb.

A stage is a recipe, not a fixed board. Its size and its difficulty band belong to the stage; the digits are generated fresh every single time you play it. Replaying stage 40 gives you a new board of the same weight, not the one you already solved.

Difficulty is measured by how a board actually solves, not by how many clues it starts with — on a grid this small those two things barely relate. Each board is replayed the way a person would solve it, and banded on how long the chain of deductions runs and how hard each link is to spot:

• Gentle — every square falls out from what is already around it.
• Steady — the same, but the chain runs longer before it ends.
• Tricky — somewhere you have to stop asking what fits a square and start asking where a digit can live in a unit.
• Brutal — a long chain with more than one of those moments in it.

Hints, and What They Cost

A hint gives away as little as it can. If one of the digits you wrote is wrong, it tells you which one and says nothing else — and that first rung is free, because being stuck behind your own mistake is not a puzzle. Beyond that, a hint points at a unit that has only one home left for some digit, or a square with only one candidate remaining, and lights it up on the board so you can see the reasoning rather than just the answer. Fill it in writes it for you if you would rather move on.

Hints past that first rung break your run. The run counts hint-free clears in a row, and it is the number worth chasing once the ladder stops being difficult.

Settings, and What Auto-Check Really Does

Five switches sit behind the gear, and every one of them changes what the board shows you rather than what it will accept. You can hide the clock, light up the unit you are working in, put the remaining count on each pad key, or drop a digit from the pad once all six are placed.

Auto-check flags a clash — a digit sitting in the same row, column or box as a copy of itself. It deliberately does not flag a digit that is merely wrong. A wrong digit that has not clashed with anything yet is a mistake you are supposed to find, and reddening it would hand you the puzzle. That is what the hint is for.

Why Play Mini Sudoku Here?

No sign-in, no daily limit, no waiting until tomorrow for the next board. It runs in the browser on a phone or a desktop, it works with a keyboard, and it respects a reduced-motion setting if you have one on.

Your progress — cleared stages, best times, your run and your badges — is kept in your own browser, so you can close the tab mid-ladder and pick it back up where you left off. Nothing about it leaves your device.

More Puzzles to Play

• Patches — fill a grid with rectangles, one numbered clue each. Same neon board, a completely different kind of thinking.
• Queens — one crown per row, column and colour region, and no two touching.
• Magic Sudoku (Easy) — the full 9 × 9 grid, gently.
• Magic Sudoku (Medium) — the step up once 6 × 6 stops slowing you down.
• Magic Sudoku (Hard) — long chains and very few clues.
• Samurai Sudoku — five overlapping grids solved as one.