Cross-clue technique · Expert
Disjunction Transitivity
When two either/or clues share one half, and their other halves contradict each other, the shared half must be true.
Why it works
If the two clues' unique halves can't both hold, one of them must fail — but since each clue needs one side or the other to be true, the shared half is the only part that survives every scenario.
Trigger
Two either/or clues sharing one branch, where their other two branches are mutually exclusive.
Common mistake
Treating two either/or clues as unrelated just because they don't share every term, instead of checking whether their shared half is being propped up from both directions.
Example
'Mina has the llama or Theo has the cat' and 'Rae has the llama or Theo has the cat' — Mina and Rae can't both have the llama, so Theo has the cat, forced by both clues at once.
On Bambleweeny's board
Implemented in the live solver as the 'Apex Coupler', enabled only at Expert difficulty.