A daily logic mystery you can actually deduce
Casebook is a short mystery for a coffee break. Read the case, mark what the clues tell you in your notebook, and follow the reasoning until only one arrangement is left. When you close the case, Casebook shows every step of the deduction, so you can see exactly why the answer is the answer.
Each case is written for Casebook, checked by a solver against every possible arrangement, and read again for wording that could mislead. How to play · How the cases are made
Questions
Is Casebook free?
Yes. Every case, the daily case and the archive are free to play in your browser. There is no account and no sign-up.
How do you solve a case?
Each case has three people, three places and three objects. Every person was in exactly one place and had exactly one object, and no two people shared either. Use the clues to work out the whole arrangement in your notebook, then name the person who was in the incident’s place with the incident’s object.
Is there really only one answer?
Yes. Before a case is published, a solver checks it against all 36 possible arrangements and only accepts it if exactly one fits every clue. A second, independent checker re-checks every case and every step of its explanation, and each case is read for wording that could mislead.
Are any clues lies or tricks?
No. Every clue is true and means exactly what it says. There are no liars, no hidden times and nothing you need to know from outside the case. The story around the clues sets the scene but never adds a clue of its own.
Is there a new case every day?
Yes. The daily case changes at 00:00 UTC and is the same for everyone. Solve it on the day to build a streak; a case you start on its day still counts if you finish by 02:00 UTC the next morning. Past dailies stay in the archive, and every case is open for practice at any time.
Can I get a hint?
Yes. A hint shows the next step that follows from the clues and names the clues it uses. If one of your marks can’t be right, the hint points that out first. You can also reveal the full solution, which ends that attempt.
Does my progress save?
Yes, in this browser, after every mark. Close the tab and come back later: your notebook, time and hints are still there. My casebook shows your streak and solved cases. Nothing is uploaded.