Frequently asked questions

None, on any platform, for anyone. There is no advertising SDK in the app at all: no banners, no interstitials between puzzles, no rewarded videos offering a hint. Because there are no ads, removing them is not something the subscription sells you.

Completely. Puzzles are generated ahead of time and ship inside the app, so every difficulty level, the Daily Challenge, the technique library and the tutorial all work with the network switched off. Leaderboards and achievement syncing are the only things that need a connection.

Yes. Downloading and playing is free, including all six difficulty levels, the Daily Challenge, the interactive tutorial and every technique lesson. An optional subscription adds premium and custom themes, the Daily Challenge archive, and larger hint and mistake allowances.

A hint does not just reveal a number. It finds the easiest of 37 human solving techniques that applies to your exact position, highlights the cells that prove it, and steps through the reasoning in plain language before placing anything. If you use one, the Coach's Report afterwards tells you which technique to review.

By the hardest technique a puzzle forces you to use, not by how many numbers it starts with. Every puzzle is solved by the same engine that gives you hints, and filed under the hardest step that solve required. The six levels are explained here.

iPhone, iPad and Apple silicon Macs through the App Store, and Android phones and tablets through Google Play. The iPad and Mac versions have their own layouts, with Split View, Stage Manager and hardware keyboard support.

The app is available in 47 languages, and you choose yours in Settings independently of your device language. Hints, lessons, the glossary and the tutorial are all translated, not just the menus.

No. The current puzzle auto-saves, including your notes, and reopens exactly where you left it. Statistics, streaks and achievements are stored on the device.

A mode with no timer, where mistakes never end the game. Nothing in a Zen game counts toward your statistics or your streak, so it is there for when you want the grid without the scoreboard.

Two ways. The Coach's Report after a finished game shows your mistakes and hints, replays up to three of those moments on your own board, and names the techniques worth reviewing. Replay plays the whole game back move by move, notes included.

Premium themes and the custom theme builder, the Daily Challenge archive so you can play days you missed, and larger hint and mistake allowances. If a subscription lapses, your stored preferences are kept and simply fall back to the free defaults.

No, and deliberately. The guides here explain how each technique works so you can find the move yourself; the app does the rest by teaching rather than answering. If you want a worked example of any technique, every technique page has one you can step through.

There is no official count, because techniques overlap and some are special cases of others. This app implements and teaches 37, from Last Remaining Cell up to 3D Medusa, which covers everything a human solver needs for the hardest puzzles it ships. The full list is here.

Rubigo Games, an independent developer. Questions, bug reports and feature requests go to [email protected], and there is a feedback form inside the app that reaches the same place.