Sudoku looks like a maths puzzle. It isn't. There's no arithmetic, no adding or multiplying — just a quiet grid, nine symbols, and a single rule. That simplicity is exactly why it has calmed the minds of hundreds of millions of people on trains, in waiting rooms, and in bed before sleep. This is the only guide you'll need: we'll start from "I've never placed a number" and walk all the way to the techniques that crack genuinely hard grids — and we'll do it gently, the My Zen Zone way.
By the end you'll understand the one rule, the anatomy of the board, every core solving technique from scanning to the X-Wing, exactly how to play the free Sudoku built into My Zen Zone, and why so many people treat a nightly Sudoku like a small meditation. Grab a warm drink. Put on something soft in the background — we'll come back to that — and let's begin.
What's inside
- What Sudoku actually is
- The one golden rule
- Anatomy of the grid
- Playing on My Zen Zone
- Your first solve, step by step
- Technique 1: Scanning
- Naked & hidden singles
- Pencil marks done right
- Naked & hidden pairs
- Pointing pairs & box-line
- A taste of the X-Wing
- Common beginner mistakes
- Climbing the difficulty ladder
- Sudoku as a calming ritual
- Frequently asked questions
- The one-page cheat sheet
What Sudoku actually is
A Sudoku is a 9×9 grid — eighty-one small cells arranged in nine rows and nine columns. That big grid is also divided by slightly heavier lines into nine 3×3 boxes (sometimes called blocks or regions). When a puzzle begins, some cells already contain numbers. These are the givens, or clues. Your job is to fill every empty cell with a digit from 1 to 9 so that the finished grid obeys one rule — which we'll get to in a moment.
The numbers 1 to 9 are really just nine distinct symbols. You could play Sudoku with nine colours, nine animals, or nine letters and nothing would change. There is no counting, no sums, no "carry the one." This surprises people who avoid Sudoku because they "aren't a numbers person." You don't need to be. If you can tell nine things apart, you can solve Sudoku. It is a game of pure logic and pattern — of ruling things out until only the truth remains.
Every proper Sudoku has exactly one solution, reachable by logic alone. You should never have to guess. If you feel forced to guess, it almost always means there's a deduction on the board you haven't spotted yet — not that the puzzle is unfair. (The My Zen Zone generator guarantees a unique solution for every puzzle it creates, which is why you can always trust that a careful, patient approach will get you home.)
The one golden rule
Here it is, the entire game in a single sentence:
Each row, each column, and each 3×3 box must contain the digits 1 to 9 exactly once.
That's it. No digit may repeat within the same row. No digit may repeat within the same column. No digit may repeat within the same box. Said the other way around: in a finished puzzle, every row holds a complete set 1–9, every column holds a complete set 1–9, and every box holds a complete set 1–9 — no gaps, no duplicates.
Almost every clever technique you'll ever learn is just this rule wearing a different outfit. When you're stuck, whisper it to yourself: row, column, box — where can this digit legally live? Solving is the art of using those three constraints together to squeeze the possibilities in a cell down to exactly one.
Anatomy of the grid
Let's get our vocabulary straight, because the rest of the guide leans on it. Below is a real Sudoku in its starting state. The darker numbers are the givens.
- Cell — one of the 81 little squares. A cell holds a single digit.
- Row — a horizontal line of nine cells, left to right. There are nine rows.
- Column — a vertical line of nine cells, top to bottom. There are nine columns.
- Box (block/region) — one of the nine 3×3 groups marked by the heavier borders.
- Given (clue) — a number printed at the start. You never change these.
- Candidate — a digit that could still legally go in an empty cell. A cell might have several candidates early on; solving is the process of eliminating them until one remains.
- Unit — a general word for any single row, column, or box. Every cell belongs to exactly three units: one row, one column, one box. Those three units are the cell's whole world.
Hold on to that last idea, because it's the key to everything: a cell is constrained by its row, its column, and its box all at once. A digit can only go in a cell if it appears nowhere in any of those three units. Combine the three and the possibilities collapse fast.
Playing Sudoku on My Zen Zone
You can play our Sudoku free in any browser — nothing to install, nothing to sign up for. Here's what the screen looks like and how each part works.
Choosing your difficulty
When you start a new game you pick Easy, Medium, or Hard. The difference is simply how many numbers are given to you at the start. Easy grids hand you plenty of clues, so there's almost always an obvious next move. Medium removes more, so you'll lean on notes and the pairing techniques below. Hard strips the board back further — you'll need patience and the full toolkit. Every difficulty still has one unique, logical solution; harder just means the logic runs deeper before it reveals itself.
If you're brand new, start on Easy for a few days. There's no prize for jumping to Hard and getting stuck — the goal is a relaxed win, not a fight.
Placing a number
Tap (or click) an empty cell to select it, then tap a number on the 1–9 pad. On a computer you can just press the matching key on your keyboard. To change a cell, select it and choose a different number. Givens can't be changed — that's by design, they're the anchors of the puzzle.
Notes (pencil marks) — your most important tool
Tap the Notes button (the little pencil) to switch into note mode. Now when you tap numbers into a cell, they appear small, tucked into the corners, instead of as a big final answer. This is exactly how paper solvers scribble tiny "maybe" digits. Notes are where real Sudoku happens: you jot every candidate a cell could hold, then eliminate them as you learn more. Tap Notes again to switch back to placing final answers. We'll devote a whole section to using notes well — it's the single biggest upgrade to your solving.
Erase, Hint, and the safety net
- Erase clears the selected cell (or its notes). Mistakes are part of learning; erase and carry on.
- Hint reveals the correct number for a selected cell when you're truly stuck. Use it sparingly — a hint you earn by finding it yourself feels wonderful; a hint you lean on constantly robs you of the fun. Treat it like a friend leaning over your shoulder, not a solver doing the work for you.
- The mistake counter (0/3) gently tracks slips. It keeps a light stake in the game without punishing you — there's no dramatic "game over" screen ruining a calm evening. The timer is there if you enjoy chasing a personal best, and easy to ignore if you don't.
When the last cell falls into place, you'll get a soft congratulations. That quiet little moment of completion — the whole grid glowing, every rule satisfied — is the reward the entire game is built around.
Your first solve, step by step
Let's actually place a number together, so the ideas stop being abstract. Look again at our grid and focus on the top-left box — the 3×3 region in the corner. It already contains a 5 and a 3. We're going to find a home for a digit using nothing but the golden rule.
Here's the thinking, spoken aloud the way an experienced solver's inner voice runs:
- Pick a digit to hunt. Let's hunt the number 1. Where can a 1 go in the top-left box?
- Rule out by row. Scan each row that passes through that box. If a row already has a 1 somewhere, then no cell in that row inside our box can be a 1 — the row already used its one and only 1.
- Rule out by column. Do the same for the three columns passing through the box. A column that already owns a 1 blocks every cell of that column.
- Rule out by box. If the box already had a 1, we'd be done — the box is satisfied. It doesn't, so we keep going.
- See what survives. Cross out every blocked cell. If exactly one empty cell in the box is left un-blocked, that cell must be the 1. There's nowhere else legal for it to go.
That move — "this digit has exactly one legal home in this box" — is the beating heart of Sudoku. You just did real deductive logic. No guessing, no arithmetic, only elimination. Every technique that follows is a more powerful way of doing this same thing.
Solving isn't about knowing what goes in a cell. It's about proving that nothing else can.
Technique 1: Scanning (cross-hatching)
Scanning is the first technique everyone learns and the one you'll use most for the rest of your life. It's exactly what we just did, done systematically. You take one digit at a time and sweep it across the board, asking each box, "given the rows and columns already using this digit, where's the only place I can still live here?"
In the figure below we're scanning the digit 7. The shaded row and column already contain a 7, so those lines are "poisoned" for 7 — no cell they cross can be a 7. In the highlighted box, that leaves exactly one open cell. The 7 has to go there.
To scan efficiently, don't wander randomly. Work in an order and stick to it:
- Go digit by digit. Pick 1, sweep all nine boxes, then pick 2, and so on. It's tempting to jump around, but a disciplined sweep catches placements you'd otherwise miss.
- Start with the busiest digits. Whichever numbers already appear most on the board are the easiest to place next, because there are more rows and columns already blocking them.
- Look at crowded boxes. A box that already has six or seven givens has very few empty cells, so a single scan often forces one.
On an Easy grid, patient scanning alone will often carry you to the finish. On Medium and Hard you'll scan until it dries up, then switch to notes and the pairing techniques. But scanning always comes first — it's free progress with no bookkeeping.
Naked singles and hidden singles
Two ideas share the word "single," and telling them apart will sharpen your solving enormously.
The naked single
A naked single is a cell that has only one candidate left. You look at that empty cell, check its row, column, and box, and discover that eight of the nine digits already appear somewhere in those three units. Only one digit is missing everywhere — so that digit is forced into the cell. It's "naked" because the answer is sitting right there, undisguised, the moment you check the cell's three units.
Naked singles are easiest to spot once you've written candidate notes: a cell showing a single little pencil mark is a naked single, ready to be placed.
The hidden single
A hidden single is sneakier and, honestly, more satisfying. Here a cell might appear to have several candidates — but when you look across its whole unit, one particular digit has nowhere else in that unit to go. Even though the cell isn't down to one option by itself, that digit is "hidden" among the candidates because it can only live in this one cell of the row (or column, or box).
Example: in a given row, suppose the digit 4 could — on candidate grounds — sit in three different empty cells. But two of those cells are blocked from being a 4 by their columns or boxes. That leaves one cell as the only possible 4 in the entire row. It's a hidden single: the 4 goes there, regardless of what other candidates that cell seemed to have.
Scanning, in fact, is just a way of finding hidden singles inside boxes. When you branch out and hunt hidden singles in rows and columns too, you'll break open positions that looked frozen.
Pencil marks done right
When simple scanning stops producing placements, notes are how you keep going. Done well, they turn an intimidating grid into a solvable one. Done carelessly, they become a cluttered mess you stop trusting. Here's the disciplined approach.
- Fill candidates honestly. For each empty cell, note every digit that isn't already present in its row, column, or box. Yes, it's a little tedious at first. It's also the foundation of every advanced move.
- Keep them current. The instant you place a digit, erase it from the notes of all cells sharing that row, column, or box. Stale notes are the number-one cause of "impossible" grids that are actually fine.
- Read the notes like a map. A cell with one note is a naked single — place it. A digit appearing once in a unit's notes is a hidden single — place it. Two cells in a unit sharing the same two notes are a naked pair — a lever for elimination (next section).
- Trust the pencil. Once your notes are accurate and current, believe them. Nearly every intermediate technique is simply a pattern within your notes. If the notes are right, the pattern is real.
In the My Zen Zone Sudoku, the Notes button makes all of this frictionless — tap it on, tap in your candidates, tap it off to place a final answer. Many players leave notes on almost the whole game and only switch off to lock in a confirmed digit.
Naked pairs, hidden pairs, and triples
Here's where solving starts to feel like magic — except it's still just the golden rule, applied to your notes.
The naked pair
Imagine two cells in the same unit (say, the same box) whose notes are identical and contain exactly two candidates — for instance, both cells can only be a 4 or a 7. You don't yet know which cell is the 4 and which is the 7, but you know something powerful: between them, those two cells will use up the 4 and the 7 for that entire unit. Therefore no other cell in that unit can be a 4 or a 7. You may safely erase 4 and 7 from every other cell's notes in that box. Those erasures frequently create new naked or hidden singles elsewhere — the chain reaction that makes harder puzzles fall.
The hidden pair
The hidden pair is the mirror image. Suppose, within one unit, the digits 2 and 6 each appear as candidates in only the same two cells — and nowhere else in that unit. Then those two cells must be the 2 and the 6 (in some order), even if they also currently list other candidates. You can erase all their other candidates, collapsing both cells down to just 2 and 6. It's "hidden" because the pair is buried among extra notes until you go looking for it.
Triples and beyond
The same logic scales. A naked triple is three cells in a unit that together use only three candidates (they don't each need all three — just no digit outside the trio). Those three digits are locked to those three cells, so you can erase them from the rest of the unit. Quads exist too, though you'll rarely need to hunt them consciously; by the time a quad matters, other techniques usually have opened the grid already.
Don't feel you must memorise these as rules to recite. What matters is the underlying instinct: when a set of N cells in a unit can only hold the same N digits, those digits belong to those cells and can leave everyone else's notes. Everything else is a special case of that.
Pointing pairs and box-line reduction
These two techniques exploit the way boxes and lines overlap, and they're the bridge from "advanced beginner" to "solid intermediate."
Pointing pairs (and triples)
Sometimes, within a single box, a digit's only candidates all sit in the same row (or the same column) of that box. Picture a box where the only cells that could be a 3 are two cells lying in the same row. You may not know which of the two is the 3 — but you know the 3 for that box lives somewhere on that row inside the box. Since the box's 3 is on that row, the 3 cannot appear anywhere else along that row outside the box. So you can erase 3 from the notes of the rest of that row. The pair inside the box "points" down the line and clears it.
Box-line reduction
This is the same idea running the other direction. Suppose, looking at a row, the only cells that can hold a 3 all fall within a single box. Then the 3 for that row is trapped inside that box — which means the 3 cannot appear in the box's other two rows. You erase 3 from the rest of the box. The line constrains the box.
Pointing pairs and box-line reduction feel almost identical because they are two faces of one truth: a digit confined to the overlap of a box and a line must live in that overlap, freeing every cell outside it. Learn to notice when a candidate is "stuck on a line within a box," and a surprising number of hard-looking positions will loosen.
A taste of the X-Wing
You do not need the X-Wing to enjoy Sudoku, and you can happily solve Easy and most Medium grids without ever meeting it. But it's the first of the "wow" techniques, and understanding it tells you the ladder keeps climbing as far as you care to go.
An X-Wing works on a single digit — say 5. Suppose you find two rows in which the digit 5 has candidates in only the same two columns. So in row A, the 5 can only be in column 2 or column 7; and in row B, the 5 can also only be in column 2 or column 7. These four cells form the corners of a rectangle. In each of those two rows, the 5 must sit in column 2 or column 7 — which means, between the two rows, columns 2 and 7 will each receive exactly one of those 5s. Therefore the 5 cannot appear anywhere else in column 2 or column 7. You erase 5 from the rest of both columns.
It's a rectangle-shaped deduction, and the first time it works it feels like you've pulled a rabbit from a hat. But look closely and it's the naked-pair idea again, stretched across two lines instead of one. That's the quiet lesson of Sudoku: every "advanced" trick is an old friend in a bigger coat. Master scanning, singles, and pairs, and you already own the reasoning behind almost everything above them.
Common beginner mistakes (and how to avoid them)
- Guessing too early. If you're guessing, there's a deduction you haven't found. Slow down, re-scan, refresh your notes. The answer is on the board.
- Letting notes go stale. Placing a number without clearing that digit from neighbouring notes will eventually trap you in a "contradiction" that's really just an out-of-date pencil mark. Clean up after every placement.
- Only scanning boxes. Beginners scan boxes and forget that hidden singles hide in rows and columns too. Sweep all three kinds of units.
- Filling the obvious and then freezing. When scanning dries up, that's your cue to commit to full notes — not to abandon ship. The middle of the puzzle is where notes earn their keep.
- Rushing. Sudoku rewards a calm, even pace far more than speed. Hurrying causes the one duplicate that quietly breaks the whole grid twenty moves later.
- Chasing difficulty for ego. A relaxed win on Medium beats a frustrated stall on Hard. Play the level that leaves you calmer than when you started.
Climbing the difficulty ladder
Progression in Sudoku is really progression in which techniques a puzzle requires. Here's a rough map of how the levels feel, and what each is quietly teaching you.
- Easy — solvable by scanning and singles alone. This is where you build speed and confidence and make the golden rule automatic. Don't skip past it; it's the level that trains your eyes.
- Medium — you'll need full notes and the pairing techniques. Naked and hidden pairs, pointing pairs, and box-line reduction all show up here. This is the sweet spot for most players: engaging enough to absorb you, gentle enough to stay relaxing.
- Hard — the grid gives less away and the logic runs several steps deep before anything is forced. You'll lean on the full toolkit and, occasionally, techniques above (X-Wing and friends). Hard puzzles are a proper sit-down-with-tea affair. When one finally yields, the satisfaction is real.
A good rhythm: spend a week comfortably beating Easy, move to Medium and stay until Medium feels routine, then dip a toe into Hard. There's no rush, and no shame in dropping back a level on a tired evening. The ladder will always be there tomorrow.
Sudoku as a calming ritual
Here's why a Sudoku sits so naturally inside a wellness app like ours. The game asks for a very particular kind of attention: narrow, absorbing, and completely in the present. To place a number you have to be here, on this box, on this digit. There's no room left over for the meeting tomorrow or the message you forgot to answer. Psychologists call that absorbed, timeless focus "flow," and it's one of the most reliably restorative states a mind can enter.
Unlike scrolling — which fragments attention and leaves you oddly more tired — Sudoku gathers attention into a single, gentle point. There's a clear task, immediate feedback, and a definite, achievable end. Your nervous system reads that as safety. Shoulders drop. Breathing slows. It's a small, contained puzzle with a guaranteed solution, and in a day full of open-ended problems, that containment is a genuine relief.
A nightly Sudoku also makes a lovely wind-down ritual before sleep — far kinder to your brain than a bright feed of news. It occupies the restless, verbal part of the mind just enough to let the rest of you start to settle. Many people find a single easy grid is the perfect "lights are dimming" signal to the body that the day is done.
Pair it with sound
Sudoku and soft instrumental music are natural partners. A quiet track gives your attention a warm floor to rest on and muffles the little distractions of a room, deepening the focus. That's the whole idea behind My Zen Zone: the same calm you find in the puzzle, carried by the sound around it. Try solving with one of our sleep or focus tracks playing low — a duduk, a hang drum, gentle rain — and notice how much more easily you drop into the grid.
You can queue a track from the app, or simply put on one of our long-form ambient sessions on the My Zen Zone YouTube channel while you play right here in your browser. Puzzle in one tab, calm in the other.
Frequently asked questions
Do I need to be good at maths to play Sudoku?
No. There is no arithmetic in Sudoku at all — no adding, subtracting, or multiplying. The digits 1–9 are just nine symbols you keep from repeating. It's a game of logic and pattern, not calculation. People who "hate maths" are often superb at Sudoku.
Is every Sudoku guaranteed to have a solution?
A properly made Sudoku has exactly one solution, reachable by logic without guessing. The My Zen Zone generator checks for a unique solution on every puzzle, so you can always trust that patience will get you there.
Should I ever guess?
Not on a well-formed puzzle. If you feel forced to guess, there's a deduction waiting to be found — usually a hidden single or a stale note that needs cleaning up. Re-scan and refresh your notes before you ever resort to a guess.
What's the fastest way to start a grid?
Scan the busiest digits first — the numbers that already appear most often — and look at the boxes that already have the most givens. That's where forced placements are easiest to find, and each one you place makes the next one easier.
When should I turn on notes?
The moment plain scanning stops producing new placements. On Easy you may finish before you need them; on Medium and Hard, switch to full notes and let the pairing techniques do the heavy lifting.
How long should a puzzle take?
However long feels good. A relaxed Easy grid might take a few minutes; a proper Hard might be a happy half-hour with a cup of tea. The timer in the app is there if you enjoy chasing a personal best, and completely ignorable if you'd rather just unwind.
Is Sudoku actually good for the brain?
It's wonderful mental exercise — pattern recognition, working memory, and sustained attention all get a workout. Just as importantly, the absorbed focus it invites is genuinely calming, which is why we built it into a wellness app rather than treating it as a throwaway extra.
Can I play on my phone?
Yes. The My Zen Zone Sudoku works right in your mobile browser — tap a cell, tap a number, and the tools sit within easy thumb reach. Nothing to install.
The one-page cheat sheet
Keep this nearby until it lives in your head:
- The rule: every row, column, and box holds 1–9 exactly once.
- Scan first: take one digit at a time; find the box where it has only one legal cell.
- Naked single: a cell with only one candidate — place it.
- Hidden single: a digit with only one possible cell in a unit — place it.
- Clean up: after every placement, erase that digit from the notes of its row, column, and box.
- Naked pair: two cells, same two candidates → erase those two digits from the rest of the unit.
- Hidden pair: two digits confined to the same two cells → erase those cells' other candidates.
- Pointing pair: a digit stuck on one line within a box → clear it from the rest of that line.
- Box-line reduction: a digit stuck in one box within a line → clear it from the rest of that box.
- Never guess. If you're guessing, look again — the logic is there.
- Stay calm. Even pace beats speed. The grid isn't going anywhere.
That's the whole game — one rule, a handful of techniques, and all the quiet you can pour into it. Start on Easy, keep your notes honest, put on something soft, and let the grid do what it does best: gather your scattered attention into one still, satisfying point. Then place that final number and enjoy the little glow of a puzzle completely, logically, calmly solved.
Ready? Open the Sudoku and try your first scan — then come back for the Solitaire guide when you fancy a change of pace.