Rule presets

Internet Mahjong Server (IMS)

This rule preset represents a version of Mah Jong as it is played on the Internet Mahjong Server.

Like the MMM (Mahjong Masters Million) rules, these are hybrid rules, originally developed in Singapore, combining features of modern Chinese and Japanese Mah Jong. The pattern selection is reminiscent of modern Japanese, featuring few mid-difficult Chow and Pung patterns, and hands like All Simples, Terminal in each set, Terminal or Honor in each set,  and as the Japanese Mah Jong, the IMS rules apply slightly better scoring for patterns appearing in a concealed hand (fully concealed is also rewarded, as in Japanese Mah Jong). On the other hand, No-points hand, going out on a pair or one-chance Chow, and other typical Japanese low-scoring patterns have been abandoned (mainly because these are typically point-scoring patterns). In addition, Flowers and Seasons (which are practically never used in Japanese Mah Jong) are often used.

The IMS rules retain point scoring for basic sets (as the Japanese and classical rules), but only for Kongs, and instead of including them directly in the point calculation (and performing multiplying with doubles or faan units), use a table to convert point units (called "auxiliary points") into faan units. It is also typical that if a minimum is required (the winning hand must normally be worth at least 1 faan), the faan units produced by auxiliary points are added only if the hand meets the minimum point requirement without this bonus. The settling table, which determines the final score (based on the number of faan the hand is worth) resembles the Chinese faan-laak table, but is actually an arbitrary table not based on the concept of limit (laak), and multiples of it.

As in all modern Asian versions, only the winner is paid, but payments are otherwise a peculiar mix of Chinese and Japanese Mah Jong. An East winner (whether going out self-drawn or on a discard) receives his final score multiplied by 1.5 (not by 6, as in classical and Japanese Mah Jong, and East loser is not penalized, either). A non-East winner also receives his final score multiplied by 1.5, if he goes out self-drawn (this resembles the Chinese modern practice, where going out self-drawn is rewarded by multiplying the final score by 6 – each loser pays double the winner's final score). If the winning tile is a discard, only the discarder pays the winner's final score (but not for all losers, as in Japanese Mah Jong), otherwise each loser pays one third of the winner's lot. Thus, the payoff scheme rewards East (without penalizing East loser) and going out self-drawn, and mildly penalizes the discarder, but since the final score is not doubled (and especially not doubled for each loser, as in the classical rules), the actual payments tend to stay rather low.

IMS rules presented by Four Winds 2 use Flowers and Seasons, apply minimum point requirement of 1 faan (faan units produced by auxiliary points not included in the calculation), and allow extra faan for a Chow hand with no Flowers and Seasons.

Settling table

The final scores are determined by using a settling table where a certain amount of faan corresponds to a certain amount of final points. The following table shows the final payments for the winner (notice that the East winner, as well as the winner going out self-drawn, is paid 1.5 times the final score, and that the discarder pays alone, otherwise each loser pays one third).

Conversion table for auxiliary points

Points for Kongs and Flowers/Seasons are converted into faan units according to the following table (note that these bonus faan are paid only if the hand is worth at least 1 faan without the help of auxiliary points).

Related topics:
Overview
Classification of rules
Alan's Zung Jung
American Classical
American Modern
Australian
British Official
Chinese Classical
Chinese New Style
Chinese Official
Chinese Transitional
Dutch League rules
EMA Riichi Rules
European Classical
French
German
Hong Kong Mah Jong
Italian Official
Japanese Classical
Japanese Modern
Japanese Transitional
Korean Style
Mahjong Masters Million
Taiwanese 16-Tile Mah Jong
Wilmington Advanced 12-Tile rules
WMPA Rules
Comparison table