Sudoku - Classic Puzzle Game

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 supportHELPFUL 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 visualizationOverall improvements and bug fixes!