Frequently Asked Questions

Every puzzle in the book is a high-quality, honest Sudoku puzzle solvable with logic alone. However, hidden among them are puzzles with a single shaded cell. The digits inside those shaded cells spell out passwords that unlock 3 secret vaults on this website!

With the one rule: every row, column and 3×3 box holds the digits 1 to 9 exactly once. Learn how to play sudoku in two minutes, then try Puzzle 1 — an easy first grid. The book also opens with a Start Here page and 70 easy puzzles.

Yes! Full answer keys for all 200 puzzles are included in the back of the book, alongside an enciphered spoiler protection key.

You can visit our Hint Chamber for progressive, spoiler-free clues that help you find the key digits and decode the words without ruining the surprise.

No! Email is strictly optional. When you crack a vault, your reward PDF (50 Easy, 100 Medium, or 200 Hard puzzles) is available for direct instant download. We never gate your rewards behind email collection.

Yes. PuzzleSecret has no third-party trackers, no ads, no cookies, no dark patterns and no external font tracking. The site keeps its own small, anonymous visit log for the author (see ‘Do you log anything about my visit?’ below). All font assets are self-hosted directly on our servers. The puzzles themselves suit any age, but our newsletter and the Keeper's Register are for solvers aged 13 and over, and we never ask any visitor for their age, school or location.

Only the site's own events, and only in the Keeper's own log. When you arrive, speak a word, open a reward, pick up a tile, find a piece of a guest room's torn note, check its pinboard or copy its position (just how many of the four, never the position itself), open the hints page, spell out a daily puzzle's vault word (only whether its digits were solved, revealed or typed), are shown the note that a guest word opens only the first door, solve a free puzzle, work through the guided first puzzle, reach the last room or carve initials on the register, the site tells the author's private Telegram: a random 4-character solver tag (not a name, not an email, not an IP), your country (and for U.S./Canada visitors, a two-letter state or province — never a city), phone or desktop, your browser's language setting, how many times this browser has visited, how many days since its last visit, and how many vaults it has opened (just a count), which of our pages you visit, the name of the site that sent you here (for a site that isn't one we know, only its country ending such as .uk; never the page you came from), the author's own guess at how you found us, and the event itself. A word spoken at a vault door, right or wrong, is passed along as bare letters; nothing else you type ever is. No cookies, no advertising trackers, nothing sold or shared with anyone else. (The site also runs Vercel's cookieless analytics, which counts page views in aggregate and never identifies you.) Clear this browser's storage and the tag resets. Section 2 of our privacy policy sets out everything the log records.

The artwork was, and the puzzles were not. The vault illustrations on this site and the engraved border art in the book were created with Google Gemini and then hand-edited. Everything that makes the book work — all 200 Sudoku puzzles, the ciphers, the Keeper's letters and the hunt itself — was built and verified by a human. Every puzzle is machine-checked to have exactly one solution.

Volume 1 is available in paperback on Amazon Prime worldwide.