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Why there is no wriggling snake in yakuman list , i think this limit hand is unique and awesome. I got twice when i play in chinese rule game. all chinese limit hand (3 big dragon, 4 big wind,13 orphan, four kong, hidden treasure , all green, nine gates, pure terminal, heaven bless, earth bless, pure honour) has been included in yakuman list but NO WRIGGLING SNAKE??. i wonder why???

The Wriggling Snake
A pair of 1's plus 2-3-4-5-6-7-8-9, all of the same suit, and one of each wind E-S-W-N. Only the last tile, whichever it is, may be claimed (or drawn from the Wall).

You might as well ask why they don't have touchdowns in baseball, or why they don't have a "royal flush" in tennis.
The British/Western rules (which is where you'll find the Wriggling Snake hand -- NOT any Chinese rules) are completely different from the Japanese rules.
Instead of looking for reasons why different rules are different, just understand that they ARE different, and play according to the rules in use by the group you're playing with.

You have a half flush (moderate difficulty), almost a straight (moderately easy difficulty), and crap in winds (worth nothing and not terribly difficult).

For one, the hand appears much easier to aim for than most other yakuman. For two, the hand is not a legitimate riichi shape, 4 melds of 3 tiles and one pair. For three, Mr. Sloper is quite right, Welcome to the ruleset of Japanese Riichi Mahjong. May you enjoy your play with these rules, but if they do not satisfy you, I'm sure you could return to another rule-set of your liking.

Japanese mahjong can be played with numerous variations of rules and scoring combinations. There's nothing to stop you including it in your own house rules when playing with family or friends. Just don't expect to see it at clubs, parlours, tournaments, etc!

As noted, perhaps a yakuman (top limit) would be a little generous. Maybe award it a baiman or sanbaiman limit instead?

Then again, the official rules themselves aren't perfect. San Kantsu (three kongs) is so rare it should be a yakuman and Sū Kantsu (four kongs) should be a double yakuman at the very least!

I also think your serpentine hand is quite "messy" compared to the standard Japanese limit hands. It's not an especially interesting or attractive form.

Ok, thanks for explanation u guys, I just know that wriggly snake is some british style, coz i played classic chinese mahjong rule in dragon kong and there's the wriggly snake. so no wonder this hand is not so popular. but anyway i love japanese rule very much than the other rule, that make you more challenging to achieve goal. and sometime the result can be so dramatic. I just learned Japanese mahjong rules 2 months ago, and this rule make me crazy that make me more addicted to mahjong game.