Puzzles are a form of entertainment popularized in the 1960's.
 Tabletop and digital word puzzles include Bananagrams, Boggle, Bonza, Dabble, Letterpress (video game), Perquackey, Puzzlage, Quiddler, Ruzzle, Scrabble, Upwords, WordSpot, and Words with Friends
  He popularized the "knights and knaves" puzzles, which involve knights, who always tell the truth, and knaves, who always lie

