Mixed Deck Rules

This is the “Mixed Deck” ruleset, a partial ruleset designed for auto-table games, and can be added onto most existing rulesets (e.g., Shuugi House Rules). It’s just about mixing up two full sets of tiles, form two mixed-up decks, and playing those 2 decks in rotation.

I find it fun to start each game with a different 2-deck rotation, and learn the deck composition as the game progresses.

The Gist

• You start with 2 sets of tiles. They do not have to have identical backs (autotables come with 2 sets of tiles; the back color is typically different between those 2 sets).
• mix up the 2 sets, and randomly pick out half of the tiles to form 1 new set, and use the remaining half for the second new set.
• play with the 2 new sets!

New Yaku

Universal

• 1-han: using 5, 6, or 7 copies of the same face
• yakuman: using 8 copies of the same face

When using different backs

• 1-han: using exactly 7 tiles from each set

Optional Tenpai Ruling

If the base ruleset mandates that a tenpai hand be “complete-able”, then the same ruling can apply here. This rule exists for WRC 2025 but not quite for Mahjong Soul or Tenhou (see here).

Specifically, under such rules, a hand can now be completed with the 5th-8th copy of the same face (but not the 9th).

• Even if it becomes clear the current mixed set only has 5 copies of the same face.

For example, the following hands are tenpai:

• (tanki/shanpon waiting on the 5th )
• (tanki/shanpon waiting on the 8th )

The following hand is not tenpai:

• (invalid: waiting on the 9th )

Note that like in “normal” rulesets, the tenpai ruling is separate from the wait type ruling.

• A waiting hand can be not tenpai, but a tenpai hand must be waiting.
• the wait type only depends on the final block (to be) completed.
• in normal rulesets, this hand has pinfu when winning on : (even though it’s not tenpai on )
• similarly, in our ruleset, this hand has a ryanmen wait type when counting fu: (even though it’s not tenpai on )