Goal. Have the lowest total score after 13 rounds. Your score each round is the pips left in your hand. The double-blank counts 50.

The station. Each round starts with a double in the station hub: the 12-12 in round 1, then the 11-11, and so on down to the 0-0. Whoever holds it places it. If nobody holds it, players draw in turn until it turns up.

The trains. Every player has a train that runs out from the station, and there is one more train for everyone — the Mexican Train. On your turn you play one domino on your own train, on the Mexican Train, or on any train that has a locomotive on it. Anyone may start the Mexican Train with a domino that matches the station double.

Can't play? Draw one domino. If it fits, play it. If it doesn't, you pass and your locomotive goes on your train — your train is now open to everyone. The locomotive comes off when you next play on your own train.

Doubles. When you play a double, you play one more domino right away. The double must be covered before anyone plays anywhere else. If nobody can cover it, each player draws as above.

End of a round. A round ends when a player plays their last domino, or when nobody can play.

Your turn. Dominoes that fit are raised and outlined in gold. Tap one. If it fits only one train, it is played at once. If it fits more than one, gold tags appear at the end of each train it fits and as buttons — tap the one you want.

Two views. The table shows the real layout, with the trains running out from the station; the camera glides to wherever play happens. Drag to look around, pinch or scroll to zoom, and tap the overview map to jump anywhere. Lane View lines every train up in its own labeled lane with all the open ends at the right — handy on a phone. The button at the top right switches between them.

The Oracle. On your turn, The Oracle plays out thousands of possible rounds for each move you could make, and ranks your moves by the pips you are likely to be left holding. It also uses what the other players have shown: whenever someone draws or passes, that proves they had nothing for the trains open to them at that moment.