Crossword is a word puzzle that usually takes the form of a square or a rectangular grid of white- and black-shaded squares. The game’s goal is to fill the white squares with letters, forming words or phrases, by solving clues, which lead to the answers.
The origin of this genre can be found in United Kingdom almost more than a century ago. However, similar games appeared even earlier under different names in different countries around Europe and Middle East. All those early ancestors have their own unique rules, standards and sometimes even grids’ shape but from all those predecessors it was originated only one type which developed into what we called today.
Crossword grids such as those appearing in most North American newspapers and magazines usually contain a solid background of white squares. Black ink is used to draw the grid and sometimes the solver’s hints, called “clues”, which usually appear as sets of two contrasting words written in red (e.g. “Night ____” or “Prince Harry”). The black squares represent white space, i.e., unused boxes that fit between the words and the edges of each row and column.
Some crosswords also use colored squares to distinguish clues from white spaces; thus a blue square might indicate a particular type of word (verb), or green could be used for compound words or phrases (nouns and adjectives). A pink square might signal an obscure clue while brown often means it is describing a personzines feature solid areas of white squares.