- The two players, blue and red, take it in turns to place pieces
on the board. You can place a piece either on a blank square,
or on a square already occupied by some of your own pieces.
- When the number of pieces on a square reaches the critical
mass for that square (two for corners, three for edges, four
elsewhere), that square explodes, and scatters the pieces on it
in all four directions. If any of these scattering pieces lands
on your opponent's pieces, they are captured and become yours.
- If this scattering causes other squares to exceed their critical
mass, then they explode too, and so on, until either the explosions
stop or there are only one player's pieces still on the board.
- That player's the winner!
- To help you, squares that only need one more piece to explode
are coloured slightly lighter.