# form9 — Shape Sudoku

> form9 is a calm, number-free sudoku you solve with nine shapes instead of digits. The logic is identical to classic sudoku — pattern recognition, working memory, and logical elimination — but with no arithmetic and nothing to read but shapes. No ads, no tracking, fully offline. Free on iPhone, iPad, and Android, with an optional one-time Pro unlock (no subscription).

form9 is "visual sudoku" (also called "shape sudoku" or "symbol sudoku"): the digits 1–9 are replaced with nine distinct shapes — circle, square, triangle, slash, diamond, star, plus, ring, and heart. Because the symbols carry no numbers, the puzzle is language-independent and approachable for people who find numbers intimidating, while staying exactly as challenging as ordinary sudoku across multiple difficulty levels, with a daily challenge and streaks. It is a good fit for searches like "offline sudoku app", "sudoku without numbers", "ad-free sudoku", and "calm / cozy puzzle game". Built by bugsntea, an independent developer; privacy-first by design (no analytics inside the app, no third-party tracking). Available on iOS (iPhone & iPad) and Android.

## Get the app
- [Download form9 on the App Store](https://apps.apple.com/app/id6774104823): free on iPhone and iPad.
- [Get form9 on Google Play](https://play.google.com/store/apps/details?id=com.bugsntea.form9): free on Android.
- [form9 home](https://form9sudoku.app/): overview, gameplay preview, and release roadmap.

## Learn about visual sudoku
- [Benefits of Visual Sudoku](https://form9sudoku.app/benefits-of-visual-sudoku/): evidence-based look at what visual, number-free sudoku trains (working memory, attention, spatial reasoning) — and what it cannot do.
- [Articles index](https://form9sudoku.app/blog/): guides to visual, number-free sudoku.

## Sudoku Strategies
- [Sudoku Strategies hub](https://form9sudoku.app/sudoku-strategies): step-by-step solving techniques taught with shapes instead of numbers; identical logic to classic number sudoku.
- [Easy techniques](https://form9sudoku.app/sudoku-strategies/easy): scanning, naked singles and hidden singles — the methods that solve most beginner puzzles.
- [Beginner Tips & Simple Patterns](https://form9sudoku.app/sudoku-strategies/easy/beginner-tips): the one rule, scanning/cross-hatching, and the "last free cell" pattern.
- [Naked Singles](https://form9sudoku.app/sudoku-strategies/easy/naked-singles): a cell with only one possible shape because its row, column and box hold the other eight.
- [Hidden Singles](https://form9sudoku.app/sudoku-strategies/easy/hidden-singles): a shape that can go in only one cell of a row, column or box, even if that cell has other candidates.
- [Medium techniques](https://form9sudoku.app/sudoku-strategies/medium/): candidate-elimination methods for when singles run out — pairs, triples and locked candidates.
- [Naked Pairs](https://form9sudoku.app/sudoku-strategies/medium/naked-pairs/): two cells in a unit sharing the same two candidates, so both shapes are removed from every other cell in the unit.
- [Hidden Pairs](https://form9sudoku.app/sudoku-strategies/medium/hidden-pairs/): two shapes confined to the same two cells, so the extra candidates in those cells are stripped away.
- [Pointing Pairs](https://form9sudoku.app/sudoku-strategies/medium/pointing-pairs/): a shape locked to one line inside a box (locked candidates), removing it from the rest of that line.
- [Box/Line Reduction](https://form9sudoku.app/sudoku-strategies/medium/box-line-reduction/): a shape pinned into one box by a line, removing it from the rest of that box.
- [Naked Triples](https://form9sudoku.app/sudoku-strategies/medium/naked-triples/): three cells whose candidates total three shapes, removing those shapes from the rest of the unit.
- [Hidden Triples](https://form9sudoku.app/sudoku-strategies/medium/hidden-triples/): three shapes confined to the same three cells, stripping the other candidates from those cells.

## Articles
- [Is Sudoku Good for Your Brain? An Honest Look at the Evidence](https://form9sudoku.app/blog/is-sudoku-good-for-your-brain): Does sudoku actually make you smarter or protect your memory? Here's what the research shows — and what it doesn't — for sudoku and other logic puzzles.
- [Sudoku for Seniors: Why the Number-Free Version Often Works Better](https://form9sudoku.app/blog/sudoku-for-seniors): Why sudoku suits older players so well — and why a shape-based, number-free version can be easier to read, less stressful, and just as good a mental workout.
- [Why an Ad-Free Sudoku Actually Matters](https://form9sudoku.app/blog/why-ad-free-sudoku-matters): Ads, trackers and paywalls quietly wreck the one thing a sudoku is for — calm focus. Here's what 'ad-free' should really mean, and why it's worth looking for.

## Translations
- [form9 auf Deutsch](https://form9sudoku.app/de/): German homepage — the site localized in German (dieselben englischen Slugs unter /de/).
- [form9 po polsku](https://form9sudoku.app/pl/): Polish homepage — the site localized in Polish (te same angielskie slugi pod /pl/).

## Optional
- [Privacy](https://form9sudoku.app/privacy/): no ads, no tracking; puzzle progress stays on your device.
- [Terms](https://form9sudoku.app/terms/): plain-language terms of use.
- [Support](https://form9sudoku.app/support/): contact and help.