Each of your three tiles is compared with the three tiles the Charleston Assistant would pass. A tile the assistant also passes earns 2 points, a close call earns 1, and a tile the assistant would keep earns 0. Six points is a score of 100, five is 83, four is 67, three is 50, two is 33, one is 17, and none is 0.

No. It is a rule of thumb based on how your tiles group, and it does not use the NMJL card. Good players often pass differently depending on the hand they are building. The score tells you how close you were to the assistant, not how well you played.

At midnight in your own time zone. Everyone sees the same hand on the same date.

The list covers a full year of hands, so each date has its own hand and the same hand comes back on the same date a year later. Roughly one hand in six is built to teach one idea, such as a rack full of pairs or a lot of lonely winds.

Jokers can never be passed in the Charleston, so they cannot be selected.

Yes, in your own browser on this device. Nothing is sent to us. Clearing your browser data resets it, and a day you miss ends the streak.

Not in the free version: each day’s hand can be played once. An archive of past challenges and your score history are planned for Mahjong Rules Tools Pro.

Yes. The Charleston Assistant lets you enter any rack and shows what it would pass, with a reason for each tile.