Wordle has nearly 3 million players across the world and versions of it are appearing in other languages.

Roughly 1 in 5 millennials say they are playing the online word puzzle game, according to a new survey. Richard Osman and Jimmy Fallon are already Wordle addicts, and the Chase star Paul Sinha also regularly posts his results on Twitter. Brands are tweeting about the trendy game, too. Lego created its own green and yellow grid out of bricks, and the Smithsonian tweeted a picture of a green, yellow and black tablecloth from its Cooper Hewitt collection.

How does Wordle work on paper? All the rows are filled in except the last one. The level of difficultly is due to the number of correct letters shown in the grid. Each letter has a different colour: white on black = correct letter incorrect place; black on grey = correct letter in wrong place; black letter on white = wrong letter, wrong place.

Just like the online game, it a process of elimination and the clue at the top means that only one answer can be right.The introduction contains clear instructions on how to play, and answers are given at the back of the book.