The case notes
Use a row quota to colour an entropic line
This entropic line has four cells. Any three neighbours use one low, one middle and one high digit. Watch a worked example, then try the idea in a puzzle.
Put it into practice
Low · middle · high
This entropic line has four cells. Any three neighbours use one low, one middle and one high digit.
First and fourth share a group
Slide the three-cell window one place. The middle two cells stay put, so the first and fourth cells have to use the same digit group.
Only one low slot remains
A full row has only three low digits: one, two and three. Two and three are already placed later in this row. Our matching pair cannot both be low.
Only one middle slot remains
The same count rules out middle. Five and six are already in the row; only one middle digit remains for the other cells.
Both cells are high
The pair shares a group, and low and middle are impossible. Both line cells are high: seven, eight or nine. Their exact digits can wait.
Read the transcript
This entropic line has four cells. Any three neighbours use one low, one middle and one high digit. Slide the three-cell window one place. The middle two cells stay put, so the first and fourth cells have to use the same digit group. A full row has only three low digits: one, two and three. Two and three are already placed later in this row. Our matching pair cannot both be low. The same count rules out middle. Five and six are already in the row; only one middle digit remains for the other cells. The pair shares a group, and low and middle are impossible. Both line cells are high: seven, eight or nine. Their exact digits can wait.
