ConstraintInference

Build a clear reasoning trail one number at a time.

This offline logic puzzle app is designed for calm, focused sessions that fit into a few spare minutes. Each board asks you to place numbers without repeating them in a row, column, or region. The challenge grows from compact 6 x 6 starter boards to familiar 9 x 9 boards with more interconnected constraints.

Choose a puzzle by board size and chapter, continue an unfinished board, or play a daily challenge selected consistently from the built-in puzzle set. Your active board, candidate notes, timer, and undo history are kept locally so an interruption does not erase your reasoning.

Useful tools keep the focus on deduction:

• Enter a final value or switch to Candidate mode to record possibilities.
• Conflicting entries are marked with both shape and color, without changing original clues.
• Undo an uncertain move while you explore.
• Ask for up to three hints per board, each with a short reasoning explanation.
• Pause a game whenever you need a break.

After a valid board is complete, review your time, marked conflicts, and hint use. Completion records and personal bests help you see steady progress across chapters without accounts, advertising, social features, or network access.

The guide explains rows, columns, regions, candidates, conflicts, and the role of hints. Preferences include light or dark theme, sound feedback, motion effects, and conflict markers. All records stay on your device and can be cleared from Preferences.