How to play
You found a notebook. It answers your questions.
Nazo Notebook is a collection of lateral thinking mysteries, sometimes called situation puzzles. A short story seems strange because part of the explanation is missing. Ask questions to discover what really happened.
Choose a mystery
Read the stories in the collection and choose Begin. For your first mystery, try Easy and No specialist knowledge.
Difficulty describes the reasoning challenge. Knowledge describes what you need to understand the story. They are separate filters. English editions are reviewed separately; only the mysteries available in English appear here.
No specialist knowledge uses everyday reasoning. Everyday knowledge draws on familiar device or service features. Some subject knowledge uses basic mechanisms or rules. You do not need to name the technical terms.
Ask the notebook
Write one question that can be answered with yes or no. Ask about one person, place, event, or condition at a time. There is no need to guess the entire solution at once.
Where did this happen? → Did this happen indoors?
Follow the clues
Yes supports that part of your idea. No means you should reconsider it. Testing an assumption can change how you see the whole story.
Not relevant means the detail does not help explain the mystery. A reply of “The story does not say” means the story does not establish the answer; it does not mean your idea is false. Try a different question.
Tap the frame at the top to reread the story and its knowledge notes. Scroll through the notebook to read earlier exchanges.
Try a solution
When you can explain what happened and why, choose Answer below the input and send your reasoning. The causal explanation matters more than matching the wording.
Auto can distinguish questions from solution attempts. If your meaning is unclear, the notebook asks you to choose before judging it. An incorrect theory still counts as a solution attempt. You can correct how your latest message was treated.
Results are Correct, Not quite, A little more detail, or Unable to judge. Unable to judge is not a wrong answer. Clarify how the events fit together and try again.
A correct solution opens the explanation. To reveal it earlier, expand the story frame and choose Reveal answer. You will be asked to confirm.
Play at your own pace
Return in the same browser and choose Resume to reopen a saved game. Sent exchanges are kept for about 30 days; there is no transfer between devices. Japanese and English game records are separate.
Start over creates a fresh game after confirmation. Use the speaker icon in the header to turn sound on or off.
Play together with a human host
Choose Play together in the collection. One person is the host and operates their own phone. Everyone else asks questions aloud. Solo play and its saved records remain available.
The host chooses a mystery and privately opens the solution and host guide. Hide the guide before showing the phone to other players, then read the story aloud.
Use the guide to answer Yes or No. Say Not relevant for details unrelated to the explanation, or Not specified if the story does not establish a fact. Spoken questions and answers are not recorded or sent.
Accept an explanation when it connects the key events, even if the wording differs. The host can offer gentle hints when the group gets stuck. This mode uses no AI judging and displays no ads.
Q&A
How are difficulty and knowledge different?
Easy, Medium, and Hard describe the reasoning challenge. Knowledge distinguishes everyday reasoning, familiar features, and basic mechanisms or rules. Even an Easy mystery may use subject knowledge; technical terms are not required. No specialist knowledge is a good place to start.
What if the notebook cannot give a clear answer?
Ask about one specific thing, or clarify which person or event you mean. It may answer Mostly yes or Mostly no when a firm answer is difficult. Connection errors and usage limits are not story clues.
Do I only get five solution attempts?
There is no five-attempt limit. Rapid repeated submissions or service-wide limits may temporarily pause sending. Unable to judge does not count as a wrong answer; you can rephrase and try again.
Can I leave and come back?
In the same browser, Resume reopens your sent exchanges and reasoning. Records are kept for about 30 days, with the latest 50 solution attempts available. Unsent drafts are temporarily kept in the same tab.
Are the answers always correct?
Solo answers are judged by AI using the story’s facts, so mistakes are possible. After reading the solution, you can report an answer that seems wrong. In group play, the human host answers instead.
What should I avoid typing?
Questions, solution attempts, and reports are saved for gameplay and quality review. Your input may be sent to TypeSafe and OpenAI for judging. Do not include personal or confidential information. Read the privacy notice for details.