Blokus

1 Overview

Blokus is a 2–4 player abstract strategy game played on a 20×20 grid. Each player controls 21 uniquely shaped polyomino pieces in their color. The goal is to place as many of your pieces on the board as possible while blocking your opponents.

The twist: your pieces can only touch your own pieces corner-to-corner — never side-to-side. This simple rule creates surprisingly complex spatial puzzles.

2 The Pieces

Each player has 21 pieces: one 1-square piece (monomino), one 2-square piece (domino), two 3-square pieces (trominoes), five 4-square pieces (tetrominoes), and twelve 5-square pieces (pentominoes). These are the same shapes as Tetris pieces and more.

3 Setup

Each player picks a color and places all 21 of their pieces beside the board. In a 4-player game, each player starts from one corner. In a 2-player game, each player takes two colors and controls both.

4 Gameplay

Players take turns in order (clockwise). On your turn, place one piece of your color on the board following the placement rules. If you cannot place any piece, you are eliminated from further play (but the game continues).

The game ends when all players are unable to place any more pieces.

5 Placement Rules

• First move: Your first piece must cover a corner square of the board (a1, a20, t1, or t20 in 4-player).
• Corner-to-corner: Every subsequent piece must touch at least one of your existing pieces at a corner.
• No side-to-side with your own pieces: Your pieces may never share a side with another of your own pieces.
• Touching opponents is fine: Your pieces can share sides with opponent pieces — this is how you block them.

6 End of Game

The game ends when no player can place any more pieces. This happens when all players have passed consecutively.

7 Scoring

Count the squares in all pieces you were unable to place. Subtract that number from zero (so your score starts at 0 and goes negative for unplaced pieces).

• Placed all 21 pieces: +15 bonus points.
• Last piece was the monomino (1-square): +5 additional bonus points.

Highest score wins. In a 2-player game using two colors each, combine both color scores.

8 Strategy

Think Corners, Not Centers

Your pieces can only spread from corners. Early in the game, push toward the center and toward your opponents' paths to create future blocking options.

Save Small Pieces

Large pieces are easier to place early. Save your smaller pieces (especially the monomino and domino) for tight spaces late in the game.

Block Expansion Paths

Watch your opponents' corners — they need corner connections to spread. Blocking their corner points cuts off their expansion dramatically.