Sudoku (originally called Number Place) is a logic-based, combinatorial number-placement puzzle. The objective is to fill a 9x9 grid with digits so that each column, each row, and each of the nine 3x3 sub-grids that compose the grid contains all of the digits from 1 to 9. **FEATURES:** - four different difficulties - hundreds of puzzles for each difficulty - auto-save your progress for each puzzle - unlimited undo/redo - auto-fill drafts - hint system for beginners - color input system for experts - clean interface and smooth controls - google play games achievements - phones and tablets support **HELPFUL FEATURES (optional):** - selection modes: select first or number first - pencil modes: automatic or manual - keyboard configuration: three rows, two rows, one row - direction highlight: vertical and horizontal highlight - number finder: highlight all occurrences of a number - number counter: show a counter for each number - rule violations: game rule warnings highlight - keyboard highlight: shown if number count is correct or incorrect - multiple color input (advanced): use different colors to place numbers - automatic error detection: show errors automatically - permanent auto-fill: continuously fill all the drafts - bigger numbers: large font for better visualization