Help and contact
How the game works
How to play, what each setting does, and the questions that come up most. If what you need isn't here, write to jordi@vicedo.cat.
The app's interface is in Catalan. The setting names below are translated, so on screen you'll see the Catalan wording in the same place.
The rules of sudoku
The board has 81 cells in nine rows, nine columns and nine 3×3 blocks. Fill every cell with a number from 1 to 9 so that no number repeats within a row, a column or a block.
Every puzzle the app generates has exactly one solution and can be solved by reasoning — you never have to guess.
The controls
- Write a number: tap an empty cell, then the number key.
- Notes: turn on the Notes button and the keys pencil in small candidates instead of writing the number.
- Erase: clears the selected cell, whether it holds a number or notes.
- Undo: takes back your last move.
- Hint: tells you how to carry on. The number in the corner is how many you have left.
Quick mode
Press and hold a key on the keypad and that number is armed: from then on, every cell you tap gets filled with it. Handy for placing all the remaining cells of one number in one go. With notes mode on, it pencils in instead of writing.
While it lasts the board shows it: the number lights up wherever it is already placed. Every empty cell is left alone, unmarked: working out where it fits is your job.
Turn it off by tapping the same key again, or the ✕ on the chip below the board. Once no cell is left for that number, it turns itself off.
Undo doesn't erase mistakes
Undo rolls back the board, not the scoreboard: the mistakes you made and the hints you spent are not refunded. If they were, you could try number after number without paying for it.
Hints
The first time you ask for a hint on a move, the app explains which technique applies and why, and points at the cells involved. Ask again and it places the number.
Every hint costs you 20 points. How many you get per game is up to you in settings; the defaults are 3 on Easy and Medium, 4 on Hard and 5 on Expert.
The techniques it uses, easiest first: naked single, hidden single, pointing pair, box-line reduction, naked pair, hidden pair, naked triple, X-Wing and XY-Wing.
Difficulties
A puzzle's difficulty isn't the number of filled cells: it's the hardest technique needed to solve it.
| Level | Numbers to start | How far it goes |
|---|---|---|
| Easy | about 38 | naked and hidden singles |
| Medium | about 32 | adds pointing pairs, box-line reduction and naked pairs |
| Hard | about 28 | everything except X-Wing and XY-Wing |
| Expert | about 24 | every technique |
The daily challenge
Every day there's a puzzle derived from the date: it's the same one for everybody and you can replay it whenever you like — it will always be identical. Difficulty climbs through the week:
| Day | Difficulty |
|---|---|
| Monday | Easy |
| Tuesday and Wednesday | Medium |
| Thursday and Friday | Hard |
| Saturday | Expert |
| Sunday | Hard |
Finishing each day's challenge extends your streak. Miss one and the streak starts over. The day is counted using your phone's clock.
Points
| What | Points |
|---|---|
| Base per difficulty | 400 (Easy), 800 (Medium), 1400 (Hard), 2200 (Expert) |
| Time bonus | up to half the base; the whole of it if you finish in half the reference time |
| Daily challenge | +250 |
| Streak | +10 per consecutive day, up to 30 days (daily challenge only) |
| Each mistake | −40 |
| Each hint | −20 |
A game never ends with negative points: zero is the floor.
Settings
All of this lives on the settings screen and applies to new games as well as the one you have in progress.
Skin
Five of them: Paper (warm paper, serif digits), Night (pitch black, for playing in the dark), Press (black and white with red ink), Forest (deep greens) and Citrus (light and rounded). They switch instantly, nothing to restart.
Mistakes
- Mistakes allowed: 1, 3, 5 or unlimited. Hit the limit and the game ends.
- Don't let me enter wrong numbers: a number that doesn't belong never reaches the board.
- …but count it as a mistake anyway: for when you want the warning without the impunity.
Hints
Hints per game: raise it, lower it, or leave it unlimited.
Helpers
- Highlight row, column and block of the selected cell.
- Highlight the same number across the board.
- Remove notes automatically: placing a number clears it from the notes in that row, column and block.
- Timer: turn it off if the clock makes you tense. Time still counts towards your points.
Haptics and sound
Each can be turned off on its own. The sounds are short tones generated by the phone itself: they don't interrupt your music and stay quiet when the phone is on silent.
Game Center
If you sign in to Game Center, your total points and your streak go to the leaderboards and you can compare yourself with the people you follow. It's optional: without signing in the game works exactly the same and the ranking screen shows your local records.
Sign in or out from the iOS Settings app, under Game Center.
Ads
No ad ever appears while you play: the banner only shows on the home, challenge and ranking screens, and when you finish a game.
The first time you open the app we ask for advertising consent, and then iOS asks whether you allow tracking. You can change that whenever you like in the iOS Settings app, under Privacy & Security › Tracking. The privacy page explains what each answer means.
Questions that come up
I deleted the app and lost my games and records. Can I get them back?
No. Everything is stored inside the app on your device, and deleting it takes the data with it. If you back the phone up (iCloud or computer) and restore it, they come back with the backup.
Can I move my data to another iPhone?
Through a phone backup, yes. There's no syncing of our own between devices — but points you've sent to Game Center do follow you, because those live in your Apple account.
Why won't it let me write a number?
Because Don't let me enter wrong numbers is on in settings. Turn it off if you'd rather be able to make mistakes.
I undid the move, but the mistake is still counted.
That's deliberate. Undo rolls back the board, not the scoreboard: if mistakes and hints were refunded, you could try number after number without paying for it.
Can I pay to remove the ads?
There's no in-app purchase at the moment. If that's something you want, tell me and I'll think about it.
The daily challenge changes over before it should.
The day is worked out from your phone's clock and time zone. If you travel or change the time zone, the changeover moves with you.
Can I play offline?
Yes. Puzzles are generated on the phone. Offline you won't see ads and points won't reach Game Center, but the game works the same.
Will there be an iPad, Android or web version?
Right now it's iPhone only.
Contact
If you find a bug, have an idea, or something doesn't work the way it should, write to jordi@vicedo.cat. I answer myself, in English, Catalan or Spanish. Telling me your iPhone model and iOS version saves me half the investigation.