Frequently asked questions

NOTE-KU is a sudoku solving method and a free app built around it. You solve with candidate notes only: a Notation Pass guided by the Two-Candidate Rule, then elimination and iteration until every empty cell holds exactly one candidate, then a single Final Pass that confirms the whole board. The full method.

Yes. All five levels and both modes are free at noteku.app/play. Themes and digit styles are unlocked with NoteCoins earned by solving; they can’t be bought with real money.

No. NOTE-KU runs in your browser. There is nothing to sign up for. You can add it to your home screen so it opens like an app (how).

Yes. It has no chat, no account and never asks for personal information. The 6×6 Mini level is a good starting point for younger players, and children’s book editions are planned.

No. That is the most common misunderstanding. Under the Two-Candidate Rule you note a digit in a box only when it has one or two possible cells there; with three or more you skip the box and return later. Every note carries real information. Why this works.

No. NOTE-KU does not ask you to memorise a catalogue of named patterns. Digit-first notation, elimination and iteration solve the large majority of puzzles; the hardest boards use Temp Mode, a structured test by contradiction. The NOTE-KU books add a few patterns of their own (the Locked Pair, the Locked Triad, the Arrow and the Grid Read) as extensions of the same logic.

No. Guessing commits to a number and hopes. Temp Mode marks an assumption in a separate colour, follows its consequences, and keeps only what a contradiction proves: if assuming “the 4 goes here” breaks the board, the 4 must go in the other cell. How to use it.

Because the Final Pass is designed to happen once, across the whole board. Writing answers mid-notation interrupts the passes and invites mistakes. In NOTE-KU Mode the app enforces it: notes only until the threshold.

Yes. The rules are the same on paper. The Starter Pack includes a digit tracker under every grid to help you know when the Final Pass is ready.

Yes, with the same phases applied more deeply: more passes, longer chains of eliminations, and Temp Mode for the tightest spots.

Either a cell is still empty or holds two notes, or one of your notes is wrong — the threshold only triggers on a fully correct candidate map. Look for a digit noted twice in the same row, column or box.

Hold the Erase button for about 0.7 seconds: every note is cleared and the givens stay. If you did it by mistake, tap Undo once to bring everything back.

Hold the Undo button. It keeps rewinding your moves in reverse order, faster the longer you hold, and stops when you let go.

The digit is exhausted for this pass: every box already holds it, has one or two notes for it, or still has three or more open cells. Move to the next digit.

Yes. Choose “Create Your Own Puzzle”, type in at least 17 givens and the app checks it has exactly one solution before you play.

No, on purpose. Building the notation is the method. The app helps with highlights, NOTED badges and an Erase-all hold, but the notes are yours.

In your browser, on your device. That keeps it private, but progress doesn’t transfer between browsers or devices. A puzzle in progress lasts while the app is open.

A printable 23-page PDF with 30 puzzles (6 each at Mini, Beginner, Intermediate, Advanced and Extreme), the method on one page, a digit tracker under every grid and full answer keys. Every puzzle has exactly one verified solution. $4.99.

For now, by email: contact@note-ku.com. We reply with payment details (USDT, BTC or ETH) and send the PDF once payment arrives. Card payments are coming soon.

The series is in preparation. Follow this site for news; the Starter Pack is the best way to start on paper today.