Take any board which begins empty. The game proceeds in 5 steps
1. Player 1 decides three things, which he must convey to player 2:
1. what the pattern will be;
2. whether the builder or blocker will receive free moves in step 3;
3. how many free moves that player will receive.
2. Then, player 2 decides which player is the builder, and which is the blocker.
3. Either the builder or blocker takes free moves as specified in step 1.
4. Starting with the builder, the players alternate moves.
5. The game ends either when the board is completely full or the pattern has been built. If the pattern has been built, the builder wins. Otherwise, the blocker wins.
Condensed MindNinja rules ganked from Trabsac Sagme's Diaries.
