Start with these ideas
- Unseen tiles are an upper bound, not tiles guaranteed to be in the wall.
- After every claim, recalculate how you can reach the minimum.
- A previously discarded tile is not automatically safe.
Count copies, not just names
A 4–5 Characters fragment can make a Chow with 3 or 6 Characters. If none is in your other tiles and the public area shows three 3s and one 6, at most one 3 and three 6s remain unseen: four copies, not eight. Do not count an opponent’s claimed discard again after it has moved into a meld.
Unseen copies can be in opponents’ hands or the wall. They are not guaranteed draws and not a win probability. Check the whole hand too: the same tile may be needed for a pair or another incomplete set.
Use 4 minus copies in your hand minus distinct public copies for each useful tile type. This counts unseen supply, not a full efficiency ranking: compare whether a draw actually reduces the work left in the whole hand, keeps a pair and preserves a legal scoring route.
A faster shape can lose a scoring route
A concealed All Chows hand on a discard has 2 faan here. Self-draw makes 3. Calling a Chow removes the concealed bonus: the same open shape has 1, or 2 on self-draw. Without another qualifying bonus it still cannot win on a standard table.
Before a claim, answer two separate questions: does it reduce the work needed to complete the shape, and where will the minimum faan come from afterward? An available button only proves the action is legal.
The figures above assume no flowers or other bonuses under our browser rules. An exposed Half Flush already supplies 3 shape faan here, so opening a useful set can preserve its minimum route. The lesson is to recalculate after the claim, not to refuse every open hand.
Treat discards as evidence, not certainty
A player showing two same-suit melds may be building a flush, but that does not reveal their pair or winning tile. Compare the cost of opening a new dangerous suit with keeping your own useful tiles. When your hand is far from a legal win, sacrificing one useful tile may preserve points.
A tile an opponent discarded earlier is not automatically safe against them now. Their hand can change, and a new discard can still be claimed.
For example, if an opponent shows two Dot melds and has discarded Characters and Bamboo, recheck a Dot you planned to discard. If your own hand is still far from 3 faan, avoid chasing an extra bonus without considering that risk. This evidence does not reveal an exact wait or make an honour automatically safe.
Let the match score inform the risk
In a four-round match, leading and trailing positions change what a risk is worth. A small legal win can end the hand; chasing a cap can expose you to a larger loss. Use the actual payment formula: house discard loss is 3 × 2^faan up to 8 faan, while self-draw payments differ.
Practise by stating your reason before looking at a hint: shape progress, faan route, visible supply and risk. Review the settlement afterward; a lucky draw does not prove the earlier decision was sound.
Check your understanding
For the 4–5 fragment above, three 3s and one 6 are public. How many helpful copies remain unseen at most?
Choose a statement to see the explanation.
A few things to know
Does a two-sided wait always have eight useful tiles?
Eight is only the starting count of two tile types with four copies each. Subtract your own and public copies. Unseen copies can still be in opponents’ hands, and the completed shape may fail the faan minimum.
Are previously discarded tiles safe in Hong Kong mahjong?
Not automatically under our house rules. Hands can change, and a previous discard does not create permanent immunity from a later discard win. Judge the current visible information rather than importing a Riichi furiten assumption.
When should I switch from attack to defence?
Reassess after important tiles appear or opponents claim. Compare your distance to a legal win, remaining supply, visible danger and match score. No fixed turn number or isolated tile guarantees the right decision.