About Casebook

Casebook is a small daily logic mystery made by Idistic, the product studio of TWINDLE NEDERLAND B.V. It’s for anyone who likes a story with their deduction: a case you can read in a minute and solve in a few, with an answer you can prove.

Fernley and its people

All cases take place in Fernley, an invented seaside town, with the same twelve people turning up again and again. The town, the people and every case are fiction written for Casebook. The portraits are original drawings, made in code.

How each case is made and checked

• The story, the people, the places and the answer are written by hand. Clue lists may be proposed by a helper program, then they are chosen, checked and frozen; nothing is generated while you play.
• A solver checks every case against all 36 possible arrangements and only accepts it if exactly one fits every clue. The clue text is produced from the clue itself, so the words and the logic can’t drift apart.
• The step-by-step explanation is built from the same clues. A second, independent checker re-checks every case and confirms that each explanation step really follows from what it cites.
• Every case is then read again, as a player would, for anything in the story that could hint at the answer or contradict it.

Spotted a clue that reads two ways? Tell us at support@twindle.nl and we’ll fix it in a new version of the case.

Credits

Cases, writing, portraits and code: Idistic, 2026. Typeface: Bricolage Grotesque, used under the SIL Open Font License (licence). The case text uses your device’s own book typeface.