Sudoku is a logic-based number-placement puzzle. The objective is to fill a 9x9 grid so that each column, each row, and each of the nine 3x3 boxes (also called blocks or regions) contains the digits from 1 to 9 only one time each. The puzzle setter provides a partially completed grid. Detail about Sudoku on Wikipedia Features: 1) 10 level difficulty 2) Training Mode 3) Skins (7 internal skins + color corrector + download other skins from AlphaSkins and put to "Program Directory/Skins") 4) Marks (Click the right button on the box, make mark and also the right button to close the pop-up window) 5) Time passing 6) It work under Windows and Linux with wine (without skins) 7) Does not require installation 8) All settings (if you their change) save in file in folder with program 9) On Esc program hide in task manager 10) Free Software