Hong Kong style, four players. The goal is a hand of four sets and a pair: a set is three of a kind (a pung), four of a kind (a kong), or a run of three in one suit (a chow).
On your turn you draw a tile and discard one. When someone discards a tile you can use, you may claim it: pung or kong from anyone, chow only from the player on your left. A claimed set is laid face up. Shout mahjong when a discard or your own draw completes your hand.
Flowers and seasons are bonus tiles: they are set aside and replaced, and some score extra. The last fourteen tiles of the wall are never drawn; if nobody wins by then the hand is a wash and the dealer deals again.
Scoring: every hand is worth points by its fan: dragons, your wind, all pungs, a flush, self-draw, and so on. A self-drawn win is paid by all three players; a win off a discard is paid double by whoever threw the tile.
A short game is one round of the wind; the deal passes when the dealer loses.
Sounds covers the tile noises, and the slider next to it covers everything. Music plays soft ambient music. Night mode warms the screen for a dark room. Chill mode turns all three on for late nights. Every switch is remembered on this device.