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'''Space mahjong''' is a modified set of rules to [[mahjong]] originally conceived by the R18 game Itadaki jan-gari-anR. Here, the limitations on terminal tiles and honor tile are removed.  Normally, the 1-9 scale ends with 1 and 9 as terminals. In this set of rules, the number sequence is given the wrap around effect when it comes to the formation of tile groupings. Another big difference in this ruleset is that you can call Chii from any player just like if you were calling Pon.
'''Space mahjong''' is a modified set of rules to [[mahjong]] originally conceived by the R18 game Itadaki jan-gari-anR. In space mahjong, terminals may "wrap around", so sequences of 912 and 891 become possible. In addition, honor tiles may be used in sequences. Another big difference in this ruleset is that you can call Chii from any player just like if you were calling Pon.


== Tile groupings ==
== Tile groupings ==
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=== Numbered tiles ===
=== Numbered tiles ===
In regular mahjong, 1 and 9 are the ends of a sequence. In space mahjong, 9 may connect to 1 like any other tile. Therefore, terminals are no worse for [[tile efficiency]] than middle tiles.


=== Honor tiles ===
=== Honor tiles ===
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=== Tanyao ===
=== Tanyao ===
There's no more special combination generated by this ruleset. Everything works as still.
Tanyao is scored as normal.


=== Chiitoitsu ===
=== Chiitoitsu ===
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=== Chanta / Junchan ===
=== Chanta / Junchan ===
Aside from honor-tile shuntsus, there're two more available combinations of numbered-tile shuntsus: 891 and 912. This makes chanta and junchan become much easier than in regular rules.
Aside from honor-tile shuntsus, there are two more available combinations of numbered-tile shuntsus: 891 and 912. This makes chanta and junchan become much easier than in regular rules.


:{{#mjt:912m891p11s56z}} {{#mjt:1'24z}} Agari: {{#mjt:7z}}
:{{#mjt:912m891p11s56z}} {{#mjt:1'24z}} Agari: {{#mjt:7z}}


=== Honroutou ===
=== Honroutou ===
The restriction of Toitoi / Chiitoi-based hand no longer applies, as honors can be used for shuntsus.
Honors may be used in sequences, so it is possible to gain honroutou without toitoi or chiitoi.


The following hand shows how it is possible with Honroutou-nomi.
The following hand shows how it is possible with Honroutou-nomi.
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=== Kokushi Musou ===
=== Kokushi Musou ===
Opened kokushi is no longer unavailable since honor tiles can be grouped as shuntsus.
Opened kokushi is now possible, as honor tiles can be grouped as shuntsus.


:{{#mjt:19m19p119s}} {{#mjt:2'34z}} {{#mjt:6'57z}} Agari: {{#mjt:1z}}
:{{#mjt:19m19p119s}} {{#mjt:2'34z}} {{#mjt:6'57z}} Agari: {{#mjt:1z}}


Though the value of such opened hand is usually reduced for balancing purpose (e.g. 2 ~ 3 hans), since it makes kokushi musou significantly easier than menzen one.
However, open kokushi is greatly reduced in value (e.g. 2 ~ 3 han) for balancing purposes.


=== Junsei Chuuren Poutou ===
=== Junsei Chuuren Poutou ===

Revision as of 10:46, 6 April 2024

Space mahjong is a modified set of rules to mahjong originally conceived by the R18 game Itadaki jan-gari-anR. In space mahjong, terminals may "wrap around", so sequences of 912 and 891 become possible. In addition, honor tiles may be used in sequences. Another big difference in this ruleset is that you can call Chii from any player just like if you were calling Pon.

Tile groupings

Due to the wrap around effect, the terminal tiles operate just like any other numbered tile.

Numbered tiles

In regular mahjong, 1 and 9 are the ends of a sequence. In space mahjong, 9 may connect to 1 like any other tile. Therefore, terminals are no worse for tile efficiency than middle tiles.

Honor tiles

With wrap-around effect, honor tiles become significantly important, for the fact that honor-related yakus are usually in high value, as well as they can now form mentsus efficiently.

Any three different tiles of kazehais / sangenpais can be formed as a valid shuntsu. That means all of the following sets are valid:

, , , , .

Any two different tiles of kazehais / sangenpais can be formed as a valid taatsu:

  • , ryanmen waiting for both and .
  • , kanchan waiting for both and .
  • , waiting for , can be interpreted as either kanchan or ryanmen.

Four different tiles of kazehais can be formed as a 4-sided tanki wait:

  • , tanki waiting for .

Yaku

Tanyao

Tanyao is scored as normal.

Chiitoitsu

This yaku is not allowed in this ruleset.

Chanta / Junchan

Aside from honor-tile shuntsus, there are two more available combinations of numbered-tile shuntsus: 891 and 912. This makes chanta and junchan become much easier than in regular rules.

Agari:

Honroutou

Honors may be used in sequences, so it is possible to gain honroutou without toitoi or chiitoi.

The following hand shows how it is possible with Honroutou-nomi.

Agari:

Kokushi Musou

Opened kokushi is now possible, as honor tiles can be grouped as shuntsus.

Agari:

However, open kokushi is greatly reduced in value (e.g. 2 ~ 3 han) for balancing purposes.

Junsei Chuuren Poutou

Theoretically a 9-sided wait hand is no longer restricted to the regular form since numbered tiles can be wrapped around. That means such hand

Agari: (in regular rules)

can be interpreted as:

Agari: (in space mahjong rules)

Though depending on rule details this may be recognized as a valid chuuren, or maybe not.

External links