Genres
Fair-play mystery
The whodunit's contract: all clues available to the reader, no undisclosed poisons, twins or divine intervention.
The fair-play whodunit is the highly codified branch of mystery in which the reader is given every clue needed to solve the crime before the reveal. Its founding document is Ronald Knox's 1928 "Ten Commandments" of detective fiction: the criminal is mentioned early but their thoughts are never shown; no undisclosed poisons or gadgets; no supernatural agency. Every suspect needs credible means, motive and opportunity.
For the writer this is a knowledge-tracking genre above all: the reader's information state at every chapter is the game board.