If you play a double (i.e. a tile with the same dot pattern on both ends, 4-4, 2-2), you place the tile across the line of dominoes to form a T shape. Some people play that you can’t play off a double.
If you can’t play, you pick up a face-down tile from the pile.
Scores are added up at the end of each round using the unplayed tiles leftover. Players use several different complex systems to count up the score. Sadly, they elude me at this time.
I do know that dominoes games here are usually played to 200, 250 or 500 points. This takes a good few rounds to reach.
The basic concept is pretty simple. It’s popular with young children.
The skill comes in when players become aware of more than just what is on the board and in their hand. The intense stand-offs that ensue are no child’s play.
If you’ve heard of card counting, a similar concept is done with tiles.
In dominoes, there are 7 suits: ones, twos, threes, fours, fives, sixes, and blanks. Each suit has 7 tiles: ones have 1-0, 1-1, 1-2, 1-3, 1-4, 1-5, 1-6.
Your schoolroom maths is right, 7 x 7 = 49 and not 28, like the number of dominoes tiles. Some tiles overlap suits, so 1-3 is also 3-1, but they don’t repeat as there’s only one of each combination in a set of dominoes.
The best players keep track of every move and pass, and learn new information about their fellow players’ hands with every turn.
They count how many of each suit has been played, and use other players’ passes to figure out which tiles are likely still in the pick-up pile.
Teams work together to out suits that are favourable to them, and block the other team from getting rid of their tiles.