Killer Puzzles was a series of puzzle books by Kjartan Poskitt (also known for the Murderous Maths series) published in the mid-to-late nineties. They had several key differences from other puzzle books of the time: they were extremely difficult, did not have any answers or solutions, and each had a secret (usually a coded message) which you could only uncover by solving all of the puzzles. The following titles were published in the series:
- Decode the Deadliest Joke in the Universe (1993)
- Find the Phantom of Ghastly Castle (1994)
- Attack of the Killer Puzzles (1996)
- Titus O'Skinty's Gruesome Game Show (1998)
Killer Puzzles provides examples of:
- Hint System: All of the books include hints and nudges for some of the nastier puzzles, but only Find the Phantom of Ghastly Castle includes the solution (albeit written in code).
- Nintendo Hard: The series as a whole was meant to be this, and it apparently succeeded, as Poskitt got as much correspondence from adults asking for help as he did from children.
- Red Herring: Attack of the Killer Puzzles requires you to do the puzzles in a certain order to decode the secret message, with the solution to each puzzle telling you which page you need to go to next. Resultantly, there are several puzzles you're not meant to do at all to solve the book; some of these are Unwinnable by Design and have no correct answer, but others are legitimate puzzles with correct answers. There is also at least one puzzle which looks like it is a red herring because it seems that logically no page should direct you to it, but is in fact necessary to complete the book.
- Unintentionally Unwinnable:
- Early printings of Decode the Deadliest Joke in the Universe had a clock in one of the illustrations drawn incorrectly, making the puzzle impossible to solve, and a puzzle where you had to add up odd numbers and take them away from even numbers accidentally transposed the words "odd" and "even".
- A maze in Find the Phantom of Ghastly Castle went over the centre of the page, which made it difficult to tell that you shouldn't actually be able to reach some of the exits.
- Unwinnable by Design:
- If you go down the secret passageway in the stables in Find the Phantom of Ghastly Castle before you have unbolted the door in the catacombs, then you're trapped.
- Poskitt was fond of putting in deliberately impossible puzzles wherever possible.
- The big secret of Attack of the Killer Puzzles is how to do this to the book deliberately once you've completed it.
- Up to Eleven: Even by the series' standards, Attack of the Killer Puzzles is an exceptionally hard book, and Poskitt admitted that other publishers might not have let him get away with it.