Backgammon
Backgammon in the browser: race your fifteen checkers home and bear them off before your opponent does. It plays on a phone or tablet as well as a computer. The board only lights up moves that belong to a legal turn, so you play by the full rules without having to know them first.
How to play
Press ROLL, then tap a lit checker. If it has one place to go, it goes. If it has two, the targets light up, and a second tap on the checker plays the higher die. UNDO takes back steps inside your turn, and the turn ends once your dice are used.
Land on a lone checker and it goes to the bar, where it must come back in before its owner moves anything else. First to bear off all fifteen wins.
A gammon (the loser bore off none) and a backgammon (the loser still has a checker on the bar or in the winner's home board) are scored. There is no doubling cube.
The rules it won't let you break
Three rules trip up casual backgammon. You must use as many of your dice as you legally can. If only one die can be played and either could be, it must be the higher one. And a checker on the bar comes in before anything else moves, while bearing off waits until every checker is home.
The game works out every complete legal turn the moment the dice land, and only offers steps that lead to one. There are no dead ends and no scolding: if a point lights up, a legal turn carries on from it.
Playing against the computer
Three opponents, named for how they play. LUCKY picks any legal turn at random. It is the easy one, backgammon for beginners: it never goes after a lone checker on purpose, so a new player gets to see how the game works instead of just losing it.
RUNNER races for home and leaves checkers exposed along the way, which backgammon punishes. ANCHOR plays position: it makes points, keeps an anchor, weighs the risk of leaving a checker alone, and hits you when it can.
Two player, by link
PASS & PLAY puts both sides on one screen. PLAY WITH A LINK opens a board and gives you a link to send, and whoever opens it sits down as the other color. Opening a board takes a password Matt hands out in person. Joining needs only the link. There are no accounts; you type a name.
Both browsers run the same rules and check every turn. The player who opened the board rolls the opening dice, and colors swap on the rematch.
This browser keeps your record: games played, wins and losses by link, a tally against each computer opponent, and gammons both ways.