CrispSudoku

CrispSudoku is a polished, ad-free Sudoku game with real depth — five rule variants, six grid sizes, and a built-in tutor that explains how to solve every board. PLAY YOUR WAY • Five variants: Classic, Jigsaw (irregular regions), Sudoku-X (diagonals), Killer (summed cages) and Thermo (digits climb along each thermometer) • Six grid sizes: 4×4, 6×6, 8×8, 9×9, 10×10 and 12×12 • Four difficulties, from Easy to Expert • A new Daily Challenge every day — the same board for everyone LEARN AS YOU PLAY • "Explain the solve" walks through any board step by step, naming each technique (naked singles, hidden singles, locked candidates, X-wing and more) • "Next logical step" hints tell you what to play next, and why • Every puzzle gets an honest difficulty rating based on the hardest technique it actually requires THOUGHTFUL TOUCHES • Pencil-mark notes, unlimited undo, and live conflict highlighting • A mistake limit that scales with difficulty • Per-difficulty hint budgets, so hints stay meaningful • Beautiful themes you unlock as you play • Achievements, streaks and detailed statistics PRIVATE BY DESIGN • 100% offline — no account, no ads, no tracking, no data collection • Every puzzle is guaranteed to have exactly one solution CrispSudoku is free software, open source under the GNU AGPL-3.0.