The XY-Chain technique is the combination of 3D Medusa and X-Chain, meaning we

  • look for alternating weak and strong links, and
  • consider links between identical candidates within a region, as well as
  • different cell candidates within a single cell.

If you have not read about 3D Medusa and X-Chain, do it now. XY-Chain brings nothing new to the table.

XY chains, unlike AICs, exclusively consider bi-value cells, i.e. cells with only two candidates.

XY-Chain Examples

the chain
the candidates we can eliminate