Grouped X-Chain
Advanced Logic29 / 32An X-Chain that moves whole box segments at once.
The X-Chain upgraded with group nodes: instead of single cells, a link end may be a whole segment — the digit's candidates inside one box-row or box-column. 'This segment holds the digit somewhere' is all the chain needs to know.
A unit whose candidates split into exactly two segments gives a strong link between groups; segments that fully see each other form the weak links. The alternating walk works exactly as before, and one of the two end groups must contain the digit.
See it in action
Step 1 of 4
The setup
When a promising X-Chain dies because a unit holds three candidates, check whether some of them huddle in one box — as a group they may act as a single chain node. Step through this real position to see it happen.
Practice
Follow the grouped X-Chain and remove its digit from the cells seeing both end groups entirely.
Drill 1 of 29Tap a cell, then the candidate digit you want to remove.