A puzzle that might have two answers is not a hard puzzle, it is a broken one. Everything about how cases are built comes down to making the promise of a single survivor safe enough to lean on.
Nothing is hand-authored
Each case is produced from a seed: the date and difficulty for a daily dossier, the track and rung for free play. The same seed always yields the same grid, which is why everyone playing today's hard dossier is looking at the identical puzzle, and why a shared link reproduces a case exactly rather than approximately.
The upside of generation is volume. The risk is that a generator will happily produce nonsense unless it is told, precisely, what a good puzzle is.
The four tests
- It ends on exactly one name. The last clue must take the field from several candidates to one. Two survivors means the chain is unfinished.
- Every clue removes someone. A clue that eliminates nobody at this point in the chain is noise, and noise in a puzzle reads as a mistake by the player.
- No clue is redundant. Remove any single clue from the chain and more than one name must survive. Otherwise the puzzle is shorter than it looks and part of your work was decorative.
- The clue tiers match the track. An easy grid is built only from clues you can answer by looking; an extreme grid leans on the ones you have to count.
Rejected, not softened
When a chain fails, the generator does not relax a requirement to save it. It throws the chain away and tries again with a different culprit or a different set of clues. A puzzle that had to be argued into existence is exactly the puzzle that will feel unfair at the last step.
There is one narrow exception, and it is recorded on the level itself: if a track cannot compose a grid from its own clue tiers, it may borrow from one tier up rather than fail entirely — an easy level may reach for a medium clue, never a hard one.
How to use the guarantee while playing
The guarantee is not trivia. It is a tool you can use on every grid:
- Two names standing means you have a clue left to apply, not that the puzzle is wrong. Walk both names against every clue.
- Zero names standing means you crossed out the culprit. Restore and redo your last step slowly.
- One name standing means you can stop checking. There is no second answer to worry about.
This is why the counter under the grid shows how many names are standing but never which. The number is a checksum; the reasoning stays yours.
What the guarantee does not promise
It does not promise a puzzle is easy, or that a chain is the shortest one possible, or that there is only one route to the answer. Often several orders of applying the clues work; picking a good one is a skill, covered in clue order. What it promises is narrower and more useful: apply every clue correctly and one name remains.
Related reading
- How to solve a deduction puzzle without guessing — A five-step method for elimination puzzles: read the clue that cuts deepest first, work name by name, slow down for counting, and use the guarantee that exactly one answer survives.
- Why crossing out suspects is so satisfying — A computer can filter a table instantly, and that is exactly why it should not. What a manual elimination does for attention, memory and the feeling of solving something.
- Daily dossiers or free play? — Three shared puzzles a day against a sixteen-rung ladder in four tracks. What each mode is good for, how streaks work, and why a replayed rung is a new puzzle.