Standard Double-12 games have 13 rounds.
Be the player with the lowest total score at the end of 13 rounds.
A standard game uses a double-12 domino set. Rounds start with the 12-12 double, then 11-11, descending each round to the 0-0 double.
On your turn, you play one domino to one of the following:
If you cannot play, draw one domino. If you still cannot play, you must place a marker on your train, making it "public" for others to play on.
When a player plays their last tile, the round ends. The winner scores 0. Everyone else tallies the pips (dots) on their remaining dominoes as penalty points.