The objective of this puzzle is to find and mark all the words hidden inside the box. The words may be placed horizontally, vertically, or diagonally. Often a list of the hidden words is provided, but more challenging puzzles may not provide a list. Many word search puzzles have a theme to which all the hidden words are related such as food, animals, or colors. The puzzles have, like crosswords and arrowords, become very popular. Also in common with these latter puzzles, have had complete books and mobile applications devoted to them.