At the end of a hand of Mah Jongg, the winner is paid based on the final score of the hand. Generally, the final score is limited to 500 points. There are, however, some extraordinary hands which simply score this limit amount. These conditions are checked first; if none of these are true, then the normal hand scoring is performed.

An additional hand that pays the limit also breaks many of the rules for a winning hand. This is the Thirteen Orphans hand, which is one each of the various terminals and honors: three dragons, four winds, three one's, three nine's and any other of the thirteen terminal and honor tiles. This requires a special-case test in Hand that short-cuts all of the evaluation algorithm.

An interesting limit hand is the Nine Gates hand, which is 3×1's, 2, 3, 4, 5, 6, 7, 8, and 3×9's all of the same suit. Any other tile of this suit will create a winning hand that pays the limit. Just considering the hand outside the mechanics of play, it would get four doubles because it is all one suit, plus the possibility of an additional double for consecutive sequences. The Nine Gates hand is only a limit hand if the player draws it as a completely concealed hand.

There are a few other limit hands, including all concealed triplets, or being dealt a winning hand. These, however, depend on the mechanics of play, not the hand itself.

Update Set Class Hierarchy. You'll want to add wind and dragon functions to the Set hierarchy. These return True if all Tiles in the Set are a wind or a dragon, respectively.

Update Hand Class. You can add six additional functions to Hand to check for each of these limit hands.

The final step is to update the finalScore to check for limit hands prior to computing points and doubles.