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Counting blocks
Block theory reads an ordinary hand as four future groups and one future pair, then compares the shapes competing for those five places.
The principle
A completed ordinary hand contains five blocks: four groups and a pair. During construction, a block may be complete, such as 345 or 777, incomplete, such as 45 or 24, or reduced to a pair or isolated tile. This view does not replace a shanten calculation, but it exposes what the hand still needs.
Rule and example
A six-block hand has one candidate too many. The right discard depends on distance to tenpai, ukeire after each option, the available pair, visible tiles and intended value. No universal rule says that the narrowest block must always be removed.
What changes
Overlapping shapes should not be split too early. A run such as 2345 can read as 234 plus 5 or 2 plus 345, with different improvements from each view. Compare complete discard outcomes instead of freezing one arbitrary decomposition.
Rules references
- Tenhou rulesReference profile used for game mechanics and scoring.
- WRC Rules 2025International rules compared whenever their options differ from Tenhou.