Blokus is a competitive tile-placement game on a 20x20 grid. Each of the 2-4 players owns 21 flat pieces in one color (the 21 distinct polyominoes of 1 to 5 squares). Players take turns adding one piece at a time, fanning out from their starting corner while blocking opponents, and try to place as many of their pieces as possible before everyone is stuck.

How to Play Blokus

Overview

Blokus is an abstract territory game for 2-4 players on a 20x20 (400-square) board. Each player takes one color and a set of 21 pieces - the 21 distinct flat shapes (free polyominoes) made of one to five squares each. On your turn you place exactly one of your remaining pieces, following two simple but strict contact rules. The game ends when nobody can place another piece; the player who got the most of their pieces down (fewest squares left over) wins.

Setup

1. Place the board between the players.

2. Each player takes all 21 pieces of one color (2 players: typically use two colors each, or play Blokus Duo; 3 players: see the 3-player note below; 4 players: one color each).

3. Decide turn order (the rules suggest blue, yellow, red, green in that rotation).

Your first piece

• Your first piece must cover one corner square of the board (each color has its own assigned corner).

Placing pieces (the two contact rules)

Every later piece you place must obey both rules relative to your own color:

1. Corner contact required: the new piece must touch at least one of your already-placed pieces at a corner (diagonally).

2. No edge contact: the new piece may not share a full edge (side) with any of your own pieces.

There are no restrictions on how your pieces touch other players' colors - opponents' pieces can sit edge-to-edge against yours. You simply may not overlap any occupied square.

Turns and getting blocked

• Players take turns in order, placing one piece each turn.

• If you cannot legally place any piece, you pass and are out for the rest of the game (the other players keep going).

• Once every player is blocked, the game ends.

Scoring (highest score wins)

At the end, each player counts the squares in the pieces they did not place:

• -1 point for every square still in your unplaced pieces (so fewer leftover squares = higher score).

• +15 bonus if you managed to place all 21 of your pieces.

• +5 additional bonus (on top of the +15) if the last piece you placed was your single-square (monomino) piece.

The best possible score is therefore +20 (all pieces placed, monomino last). The player with the highest score wins.

3-player note

With 3 players, the fourth color is shared/rotated or left out per the rules variant your edition specifies - record which house rule you used in match notes. For a clean balanced game many groups prefer 2 or 4 players, or play Blokus Duo head-to-head.

Each player scores -1 point per square in their unplaced pieces, +15 if all 21 pieces were placed, and +5 more if the last piece placed was the monomino. Highest total wins; the maximum possible score is +20.

Total Points is authoritative. Squares Remaining (count), Placed All Pieces (boolean) and Monomino Last (boolean) are diagnostic side metrics: because the squares-remaining penalty is negative and the +15/+5 bonuses are fixed positive jumps, they do not sum into Total Points, so they are recorded as observations only and never combined into the score.