Select, then enter

Tap a cell to select it, then tap a number — on the pad or your keyboard. Value writes the final answer. Candidate toggles a pencil mark instead. Press M to swap between them, arrow keys to move, 0 or Backspace to erase, and ⌘/Ctrl-Z to undo.

The selected cell is filled with the accent colour, its row and column are banded, and every cell already holding that digit is ringed — so you can see at a glance where the number is blocked.

View (the magnifier key, with Notes, Undo and Redo or beside Hint) opens a panel for reading the board. Focus on a digit picks one number: its placed digits and candidates stand out and the rest step back (your own numbers are underlined, givens are not). The inspector shows the selected cell large: its name, its number or its candidates in their usual places, and any highlight the board is showing on it. Turn on Board coordinates in Settings → Board (or with the grid button in the panel) to label rows r1–r9 and columns c1–c9, the way the coach names cells. None of these changes the puzzle or counts as a hint. During an explanation the focus pauses so every colour stays visible, and a tapped cell is shown large in the inspector without moving the lesson on.

The coach reveals in stages

Hint shows the easiest step that makes progress — a single before a pair, a pair before an X-Wing — never the solution. Choose a technique under Look for to practise that family instead. It arrives in three stages: first the pattern cells are highlighted, then the reasoning in plain language, then the elimination itself.

Stop at any stage. Seeing the pattern and working out why it holds is the part that transfers to the next puzzle. You can turn stepped hints off in Options if you would rather see everything at once.

Play and Learn

Play deals a fresh board at the level you choose. A level is what the puzzle demands, not how empty it looks: each generated board is solved by logic first, always with the simplest technique that makes progress, and rated by the hardest step that took. Easy needs singles only; Medium also needs locked candidates, pairs or triples; Hard needs one or two advanced moves; Master needs more of them, or a long one: a Swordfish or Jellyfish, an X- or XY-Chain, or an alternating inference chain. Unique Rectangles are used only on boards known to have exactly one solution — every dealt board is. New puzzle under the board deals another one at the same level.

Learn takes one technique at a time, in three steps. Learn plays the technique on a worked example: the cells and candidates each sentence is about light up as you read it, with the two cases in two colours and the elimination in red. Practise puts you on a taught position, or a fresh variation of it: for a single you find the cell and enter its digit, for every other technique you mark every candidate it removes. Challenge generates a complete Sudoku for practising the technique. For the foundations it is built from the techniques taught before it: they run out partway through and the new one gets you going again — except naked singles, the first, which finish their board on their own. For the advanced patterns, ordinary logic runs out and the technique is a way through.

A Challenge comes in two kinds, chosen on the technique's page. Focused boards finish with the technique and the foundations alone (for a foundation, with the techniques taught before it): one solving path using only those was checked to the end. Mixed boards practise the technique the same way, then may need other techniques to finish; the board lists them before you start. Neither promises the technique is the only way through, and both name any other technique that also works where it is needed. Naked Single challenges are always Focused, and Strong Links have no Challenge.

Your Play board and your Challenge are kept apart, and each tab offers its own Continue, so starting one never costs you the other.

While you play, Hint in the toolbar opens the coach on the easiest useful deduction on your board — on a phone as a sheet over the lower part of the screen — and Explain step by step plays that exact move on your grid, with your cells and your digits. On a Learn board the same button is Drill, and opens the task.

On a Challenge the pattern is deliberately not shown at the start. Solve with ordinary logic until it runs out — that deadlock is the drill, and the coach says when the pattern becomes available.

Mistakes on a Challenge

A Challenge is a real Sudoku, so wrong final digits are refused rather than accepted and punished later. A move that would make the puzzle unfinishable is blocked and counts as one mistake.

Three mistakes end the Challenge. Pencil marks are never counted as mistakes — experiment with candidates freely.

Pattern library