Differences between Zung Jung and riichi mahjong - furrykef/mahjong GitHub Wiki

This list is not intended to be exhaustive, but it comes close.

  • There is no riichi call. But you score 5 points for winning with a closed hand, whether you win by ron or tsumo.
  • The scoring system is much simpler. There is no distinction between fu, han, and points.
  • There are no dora of any kind. Note that the lack of kandora means that kongs (kans) are much more common, since the kong is much less likely to benefit one's opponents.
  • All losers pay. Up to 25 points, there is no difference between ron and tsumo. If a player declares ron and their hand has a base value of more than 25 points, then all other players pay 25 points and the discarder pays the remaining balance.
  • The dealer never pays or receives extra. The dealer is treated just like any other player.
  • Players can never go bankrupt. Because of this, we start players at 0 points instead of an arbitrary number.
  • Winds rotate after every hand, even if the dealer wins. This means a 2-round game will usually take rather less time than it would in riichi, and 4-round games are common.
  • There is no furiten. But there is a "same-turn immunity" rule which has a similar effect to temporary furiten.
  • Call swapping is allowed. You can call chi for 1-2-3 and discard a 4.
  • All yaku can be scored with an open hand, except for yaku that are closed by definition: Concealed Hand, Four Concealed Triplets, Seven Pairs, Thirteen Orphans, and Nine Gates. There are no yaku that decrease in value when the hand is open.
  • A few of the yaku are different, but not many. Note in particular:
    • There is no bonus for winning by tsumo, even if your hand is closed.
    • There is no prevalent wind; only your seat wind scores points as a triplet.
    • All Sequences (Pinfu) allows any pair and and any wait, and it can be open.
    • Seven Pairs allows four of a kind to act as two pairs.
    • Nine Gates must be "pure"; that is, you must have a 9-tile wait for it to score as Nine Gates.
    • The value of Thirteen Orphans does not depend on its wait. It is the same yaku whether you complete it with a 1-tile wait or a 13-tile wait.
    • Blessing of Earth (Chiihou) is achieved by claiming the dealer's first discard, not by getting tsumo on your first turn. It is not valid if the dealer first declares a kong.
    • Final Draw (Haitei Raoyue) and Win on Kong (Rinshan Kaihou) may be scored together.
    • The following yaku are added:
      • One Kong
      • Two Kong
      • Two Concealed Triplets
      • Small Three Winds
      • Big Three Winds
      • Three Identical Sequences
      • Four Identical Sequences
      • Three Consecutive Triplets
      • Four Consecutive Triplets
      • Small Three Similar Triplets
      • Three Consecutive Triplets
      • Four Consecutive Triplets
  • Closed kongs (kans) are completely hidden. This is actually a custom rule and not an official Zung Jung rule. The official rules say that the tiles are revealed immediately "for verification". Since this is a computer version, no verification is needed.
  • There are no abortive draws. The only draw condition is when the wall is exhausted.
  • There is no bonus for being in tenpai when the hand reaches an exhaustive draw.
  • There is no scoring minimum. A hand with no yaku (a "chicken hand") is a valid winning hand and scores a token 1 point. This makes the game rather more friendly to beginners. (There is a variant that we currently do not offer which requires a 5-point minimum, which is similar to riichi's requirement that every hand must have a yaku.)