Practical answers to the questions our editors most often receive from readers evaluating Sudoku: The Clean One.
Tap the pencil icon in the bottom action bar to toggle notation mode. Any number you enter while pencil mode is active is treated as a candidate. Switching back to regular mode lets you place final digits. Long-pressing the pencil icon opens settings for corner notes versus centre notes.
Yes. Within Settings → Appearance you can choose between System Default, Light, Dark Charcoal, and Pure-Black AMOLED. You may also schedule automatic theme switching tied to local sunrise and sunset, which is particularly useful across Australian time zones.
The app uses Google Drive App Data folders to back up your progress, statistics, and active puzzles. The backup is encrypted by Google and is not visible to other applications. You can disable cloud sync at any time and continue to use the app entirely offline.
When you select a cell containing a digit, every other cell with that same digit is softly highlighted, which dramatically simplifies scanning techniques such as cross-hatching and naked-pair detection.
No third-party advertising is included. The app offers a single one-time optional supporter purchase that unlocks alternative colour themes; it has no effect on puzzle availability or core functionality.
Yes. The complete puzzle library, including daily challenges queued in advance, is available offline. Cloud backup only synchronises when a connection becomes available.
Each puzzle is generated by a constraint solver that classifies it according to the most advanced technique required for a unique solution path. Easy puzzles need only naked singles; Extreme puzzles may require X-Wing, Swordfish or forcing chains.
Yes. The interface includes an unlimited undo stack for the current puzzle, plus a one-tap restart that preserves the original given digits.
The interface scales gracefully to tablet displays and to inner foldable screens on devices such as the Galaxy Z Fold series. Larger displays present the puzzle grid alongside the candidate side panel.
Use the in-app feedback option in Settings → Help, or visit the developer's listed contact channel on the Google Play page. The team is responsive and ships maintenance updates approximately every four to six weeks.
No. Smart2Grid is operated independently by APPIA Sp. z o.o. and produces editorial reviews without any commercial partnership with the application's developer.