Sudoku Master: Free Sudoku

The build

Built and maintained in-house as a production proof of our mobile pipeline: on-device puzzle generation, fully offline play, streaks and daily challenges, and a hint engine that walks one logical step at a time. Material 3 interface with dark mode, tested across low-end devices.

What we handled

• Puzzles generated offline on-device — no server dependency
• Hint system teaches strategies rather than revealing grids
• Stats, streaks and share-out for completed puzzles
• Ships through the same CI + staged rollout we use for clients

Why a dev studio ships its own game

Because it is the honest portfolio. An agency can show any screenshot; only its own products reveal what happens when nobody is watching the deadline. Sudoku Master goes through the full cycle we sell — engine design, UI, performance, store release, ads, privacy declarations, maintenance — on our own dime. If a detail is sloppy here, it is our sloppiness on display, not a client's.

It also answers a question we get weekly: “can you do more than websites?” A mobile game is the hard answer — 60fps rendering on a 3-year-old budget Android phone, a puzzle engine that never generates an unsolvable board, state that survives process death, and a store pipeline that keeps updates shipping without breaking installs.

The puzzle engine: generated, never shuffled

Every board starts as a full valid solution and gets clues removed under two guards: the puzzle must stay uniquely solvable, and it must demand the techniques its difficulty label promises. That is why difficulty here is real and not cosmetic — Easy falls to singles, Extreme does not fall to anything until you find the hidden pair holding the door shut.

Generation runs on-device in Dart, in milliseconds. The same solver that checks uniqueness also powers the hint ladder: when a hint fires, the engine finds the next move the current board state justifies, then picks the simplest technique that reaches it. Hints never dump the answer — they name the rule and point at the region, so the placement stays yours. Solving by guesswork stops being a strategy because the app can tell when it is happening.

Offline-first and account-free — on purpose

No login, no server, no analytics upload: the Play listing's “No data collected” declaration is not a policy concession but the architecture itself. The whole game state — board, notes, timers, statistics, streaks — lives in an on-device store, which is why the app opens mid-flight and why a dead internet connection changes nothing about the product.

For a client, the same pattern is a compliance shortcut: an app that never collects personal data has almost nothing to leak, no retention schedule to honor, and no cross-border transfer paperwork. We make the privacy posture an engineering decision at phase 01, not a legal apology in year two.

Retention loops without dark patterns

The daily challenge is the only hook the app uses: one fresh, identical-for-everyone puzzle each day, streak counting, and bonus points for consistency. No push-notification spam, no fake lives, no countdown offers. Streaks give the loop its shape; statistics pages (best times per difficulty, solved counts, win streaks) give the progress a place to be seen.

Share cards close the loop from the other side: finishing a puzzle lets you post a designed image of the completed board and your time — the only growth channel a content app genuinely needs, and one that costs nothing to maintain because it is drawn by the same renderer as the game itself.

The interface: calm is a feature

Material 3 theming across a single Flutter codebase, tuned for one-thumb play on phones and two-hand tablet layouts; dark and light themes share the same contrast tokens; the pencil-notes, undo/redo, timer pause, and real-time error highlight states are all part of one input model, so there is no weird mode-switching during play. The board itself is custom-drawn: the grid, selection shading, and peer-highlighting are painted rather than composed, which keeps the frame budget while the app animates at 60fps on entry-level devices.

Free with ads, published like a product

The listing says “Contains ads”, and we keep it that way: a banner placed where it never covers the board, rewarded interstitials offered only between finished puzzles. Monetisation that respects the flow is a design constraint, not an afterthought, and the app-size and startup budgets stay guarded like any other feature.

Release engineering is the boring flex: signed builds, staged rollouts, crash triage, and an update cadence (the listing shows a real “updated on” date, not a 2021 relic). “Relax with free sudoku offline — daily challenges, smart and fun brain puzzles” is what the store copy ends with; keeping it true week after week is the actual product work.