Blokus is an abstract strategy board game for two to four players, invented by Bernard Tavitian and first released in 2000 by Sekkoïa, a French company. It has won several awards, including the Mensa Select award and the 2004 Teacher's Choice Award. In 2009, the game was sold to Mattel.

Gameplay
The shapes of the 21 Blokus tiles.
The game is played on a square board divided into 20 rows and 20 columns, for a total of 400 squares. There are a total of 84 game tiles, organized into 21 shapes in each of four colors: blue, yellow, red, and green. The 21 shapes are based on free polyominoes of from one to five squares (one monomino, one domino, two trominoes/triominoes, five tetrominoes, and 12 pentominoes).

The standard rules of play for all variations of the game are as follows

Order of play is based on color, with blue going first, followed by yellow, red, and green.
The first piece played of each color is placed in one of the board's four corners. Each new piece played must be placed so that it touches at least one piece of the same color, with only corner-to-corner contact allowed—edges cannot touch. However, edge-to-edge contact is allowed when two pieces of different color are involved.
When a player cannot place a piece, he or she passes, and play continues as normal. The game ends when no one can place a piece.
When a game ends, the score is based on the number of squares in each player's unplayed pieces; a player loses one point for each square (e.g. a tetromino is worth -4 points). If a player played all of his or her pieces, he or she gets a bonus score of +20 points if the last piece played was a monomino, +15 points otherwise.