From First Cage
To Black Belt.
The only killer sudoku app designed to teach intuition, not guesswork. Master the 45 Rule, cage combinations, and candidate slicing with interactive drills and real-time coach insights.
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"That 2-cell cage summing to 16 in row 1 can only be 9. And 45 − everything placed reveals the outie — free digit, no guessing."
Try the 45 Rule Live in Your Browser
In this 2-cell cage with a sum of 16, one cell is already confirmed as 9. Can you deduce the outie without guessing?
Teaching Intuition, Not Guesswork
Most Sudoku apps give you a blank grid and leave you stranded. We teach you how masters see cages.
The 45 Rule
Every row, column, and 3×3 box sums to exactly 45. Learn how subtracting known cage sums reveals forced outie digits instantly.
Belt Progression
Advance from White Belt to Black Belt. Earn XP, unlock lessons, and prove your mastery in the final "Trial by Fire" with zero hints.
The Coach Rail
Never get stuck. When you ask the Coach, it breaks down the exact mathematical deduction step-by-step instead of spoiling the solution.
The 7-Lesson Technique Dojo
The Two-Pane Coach Rail
Engineered for landscape tablets, iPads, and folding devices. Full-screen tactile board on the left, permanent AI mathematical coach on the right.
Zero Board Occlusion
The 3×3 numpad and control tools are anchored to the persistent 336px right rail. Your board is never blocked by floating keypad popovers.
Live Mathematical Step-Through
Ask the Coach for advice: it shows the 45 Rule subtraction equation, cage sum breakdown, and outie candidate deduction without spoiling digits.
Hardware Keyboard Ready
Full support for Magic Keyboard, external Bluetooth keys, numbers 1-9, Space for notes toggle, and Backspace to erase.
The Daily Challenge Ritual
One synchronized puzzle worldwide every single day. Prove your mathematical intuition, earn streak multipliers, and share your solves.
Today's Dojo Challenge
Difficulty: Expert 9×9 · Par time: 14:00. Solved by 1,420 students today.
Play Daily Challenge on Web →Daily Calendar Cadence
Warm Up Your Dojo Today
Available now on Google Play for Android phones & tablets. iOS App Store release coming soon!