Copyright (c) 2000 Bernard Tavitian, Sekkoia Publ. 

This game is played on an empty 20x20 square board:

Blokus is a 4 player game (so there are 4 different colors, check it at Funagain), but the rules can also be used for just two players (each one plays two colors on two opposite corners). Each player starts with two sets of 21 pieces each:

  • DROP - Select one of the off-board pieces, if necessary rotate or mirror it (there are 8 possible options) and drop it on a set of empty cells, where at least one of the stones is diagonally adjacent to another stone of the same color, and no dropped stone is orthogonally adjacent to any stone of the same color already on board.
    • On the first and second turn, each player plays a piece adjacent to one of his corners.
    • When a color cannot place another piece, that color is dead, and cannot play anymore. 
  • GOAL - When all colors are dead, wins the player with the color with most points:
    • One point for each stone on board
    • Fifteen points extra if all pieces were dropped
    • Five points extra, if the last played piece was the single stone.
An example

In this small example with just two colors and two corners, white could play on cells [1], because it is diagonally adjacent to one white stone, and is not orthogonally adjacent to any white stone.

You can play Blokus against the computer at this website.

A few quick strategy tips from Matthew Frederick: 1. It's generally best to get to the center of the board as quickly as possible in order to build 'paths' into other players' areas while you still have a chance. 2. Leave yourself lots of well-spaced corners with your early lays (e.g. use the stair-stepped piece well away from your corner, if possible, etc.). 3. If you have a choice between laying a piece that will block another player's corners or one that doesn't, it's almost always better to block. 4. Watch for sneaky paths other players will use to slip through your pieces and, whenever possible, block them long before they get a chance (seeing someone spill into your carefully created 'safe space' is no fun at all and will force you to play defensively). 5. It's fairly obvious, but it's essential to play your complex and large pieces early in the game: you will probably not have a chance after.