Hard Sudoku

Hard Sudoku is classic 9×9 sudoku for players who got bored with easy long ago. Nine levels, from Very easy to Legend, where logic runs out and guessing begins. Nine variations: squiggly blocks instead of 3×3 squares, X diagonals, shaded Hyper and Percent areas, color groups — on their own and combined with squiggly blocks. Each has seven levels and its own statistics. 57,000 puzzles: 25,500 classic and 31,500 in variations. Each has exactly one solution — uniqueness is verified in advance. A hint does more than open a cell: it highlights the cells, names the technique and explains why the move is right. A repeated digit lights up at once, and a grid check finds the mistakes no repeat reveals. Notes, undo and redo, three input schemes, light and dark themes, sound, Russian and English. A tutorial, achievements for day streaks, puzzles solved and games without help. Games and statistics live in the cloud. Leaderboards: solved puzzles, day streaks and best time per level.