Sudoku: Classic, Samurai & X

Six ways to play Sudoku, in one free app. No ads. No in-app purchases. No paywall. Just puzzles.

SIX SUDOKU VARIANTS
• Classic Sudoku — the original 9x9.
• X-Sudoku — both diagonals must also hold every digit once.
• Windoku — four extra shaded regions add another layer of constraint.
• Irregular (Jigsaw) Sudoku — nine oddly-shaped regions replace the standard boxes.
• Killer Sudoku — no starting digits at all, just cages with target sums.
• Samurai Sudoku — five overlapping grids in a plus shape, for a genuinely long-haul challenge. (A big board: most comfortable on a tablet or a larger phone.)

DIFFICULTY THAT MEANS SOMETHING
Four levels — Easy, Medium, Hard and Expert — graded by the hardest technique a puzzle actually requires, not by how many digits were removed. An Expert puzzle genuinely needs locked candidates, pairs and X-Wings, every time. A recommendation engine watches your win rate and suggests where to go next.

LEARN TO SOLVE, NOT JUST TAP
A 12-lesson interactive tutorial covers naked and hidden singles, locked candidates, naked and hidden pairs and triples, X-Wing, XY-Wing, Swordfish, and two Killer-specific techniques (cage sums and the 45 rule). Every lesson is taught on a real board captured mid-solve — not a hand-built example.

HINTS THAT ACTUALLY TEACH
Three staged hints per puzzle. The first narrows you to a single row. The second explains which technique applies and why. Only the third fills the digit in. Solve the cell yourself before that and you get the hint back.

DAILY CHALLENGE + A FULL YEAR OF ARCHIVE
One puzzle a day, the same for everyone, worldwide. Miss one? A 365-day archive lets you go back and play any day from the past year. Both work completely offline.

PLAY WITH FRIENDS (OPTIONAL)
Send a friend a code to race the exact same puzzle, or go head-to-head in a live 1v1 match and watch each other's progress fill in as you solve. There's an opt-in public leaderboard too. (Friend challenges and live matches use Classic puzzles.)

TRACK EVERYTHING
22 achievements, per-variant and per-difficulty statistics, best times, win rates and streaks. Sign in with Google if you'd like it all backed up so it survives a reinstall — entirely optional.

BUILT FOR ACTUALLY SOLVING
• Pencil marks and candidate notes, with a fill-all shortcut
• Undo and redo
• Conflict highlighting and a check-your-board button
• Number-first input mode, auto-advance, pause and resume
• Seven themes including a true dark mode
• Sound and haptics, both toggleable
• An optional daily reminder, scheduled locally on your device

PLAYS OFFLINE
Every puzzle, the daily challenge, the whole archive, your stats and the tutorial all work with no connection at all. Only the leaderboard, friend challenges, live matches and cloud backup need the internet — and all of those are optional.

FAIR BY DESIGN
No ads. No in-app purchases. No "watch a video to continue". No energy timers. Three mistakes ends a puzzle, and hints are capped at three, because the challenge is the point.

Whether you want five relaxed minutes of Classic on a commute or a real fight with a Samurai grid, there's a board here for it.