A quick guide to every feature — from your first puzzle to sticky numbers, notes, hints, and the settings that change how the game plays.
Fill the 9×9 grid so that every row, every column, and every 3×3 box contains the digits 1–9 with no repeats. Some cells start filled — those are your clues.
Every puzzle in Simply Sudoku has exactly one solution, so you can always get there by logic alone. You never have to guess.
Tap New at any time for a fresh puzzle. If a game is already in progress you’ll be asked to confirm first, so you never lose a puzzle by accident.
Choosing difficulty: pick Easy, Medium, Hard, or Expert. Two settings decide what you get on launch — a Default level (the level every new game starts at), and “Ask me for a level when the game opens”, which pops up a quick difficulty picker each time the app starts.
Skip the confirmation: a small “Don’t warn on New” checkbox sits right beside the New button. Tick it and tapping New starts a fresh puzzle immediately, without asking. (Changing difficulty mid-game still confirms, so you can’t wipe a game just by tapping a level.)
Tap any cell and the board helps you scan it: its row, column, and 3×3 box are highlighted, and every cell holding the same number lights up too — perfect for spotting where a digit can still go.
Your original clues and the numbers you enter are always easy to tell apart.
Two ways to place a digit: tap a cell to select it, then tap a number on the keypad — or use the sticky pen (below). On a computer you can also use the arrow keys to move and 1–9 to type.
Erase: tap the selected cell’s number again to clear it, or press 0 / Delete / Backspace. Each keypad button also shows a small remaining-count badge — how many of that digit are still left to place — counting down to zero as you fill the grid.
When you want to place a lot of the same digit, make it “sticky.” Press and hold a number button for about half a second — it turns amber to show it’s now your active pen. Every empty cell you then tap gets that digit, so you can sweep through all the 7s (say) without reselecting the number each time.
Tap the pencil button (or press N) to enter Notes mode — the button stays pressed while it’s on. Now tapping numbers pencils small candidates into a cell instead of placing a final answer. When you later place a correct digit, Simply Sudoku automatically clears that candidate from the row, column, and box for you.
Stuck? Tap Hint (or press H). After a quick confirm, one correct digit appears in green on a pale-green cell, and an unobtrusive bar asks “Keep this hint?” — Keep commits it, Undo removes it.
Either way it counts toward your hint limit, which depends on difficulty (Easy allows the most; Expert the fewest). When your hints are used up, the button disables.
Undo and redo are unlimited — step back and forward through your moves with the on-screen buttons or Ctrl+Z / Ctrl+Y. A timer runs while you play, and Simply Sudoku records your best time for each difficulty, shown right on screen and celebrated when you beat it.
By default, a wrong entry is shown in red, and the status line tracks Mistakes: used / max. Each difficulty has a mistake limit — reach it and the game ends with Game Over, where you can Retry the same puzzle or start a New Game. Prefer no safety net at all? See the next section.
In Settings, turn off “Highlight wrong numbers” for a pure challenge: mistakes are no longer shown in red, the mistake counter disappears, and you can’t lose on the mistake limit.
Instead, a ✓ Check button appears. It stays disabled until every cell is filled, so you complete the whole puzzle first, then check it in one go. If it’s right, you win; if not, a “Not quite right” message lets you Keep Trying or Quit.
Tap Pause to stop the clock — the board hides behind a “Paused” panel you tap to resume. The game also pauses automatically whenever you switch away from the app, and resumes when you come back. (A pause you started by hand stays paused until you resume it yourself.)
Want to close the app and finish later? Turn on “Resume interrupted game on next launch” in Settings. With it on, an unfinished puzzle comes back exactly as you left it — board, pencil notes, timer, and mistakes — the next time you open the app. Leave it off (the default) and every launch deals a fresh puzzle. Either way, your game stays only on your device.
Two dropdowns on the main screen set the mood. Theme restyles the whole app (light, dark, warm, high-contrast and more). Board recolours just the 9×9 grid — 12 looks including Classic, Paper, Mint, Slate, Rose, Lavender, Sunset, Midnight, Forest and Charcoal.
Mix and match to taste; your choices are remembered next time.
Turn your phone sideways and Simply Sudoku reflows to a two-column layout — the board on one side, a phone-style 3×3 keypad on the other. Tap the ◀ / ▶ arrow in the keypad to swap the board and controls to the other side, so the keypad falls under your thumb whether you’re left- or right-handed. Your chosen side is remembered.
Simply Sudoku works completely offline and stores your game, best times, and settings only on your device. On Android, the app also blanks its preview in the app-switcher by default (which also blocks screenshots) so a paused puzzle can’t be studied off the clock. Want screenshots anyway? Turn on “Allow screenshots” in Settings.
| Key | Action |
|---|---|
| Arrows | Move selection |
| 1–9 | Enter digit (or note, in Notes mode) |
| 0 / Delete / Backspace | Erase cell |
| N | Toggle notes mode |
| H | Hint |
| Ctrl+Z / Ctrl+Y | Undo / Redo |
The #1 way to help — bigger than a donation
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Simply Sudoku has no ads and no advertising budget. It can’t pay to appear on the app stores — it only gets noticed when players like you leave a review. Every rating pushes it higher in search, helps new people discover an honest, ad-free game, and keeps it growing without spending a cent on ads. Great reviews are our advertising.
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Live now on both Google Play and the App Store.