The case notes
How an entropic line groups digits
Any three consecutive line cells hold one low (1–3), one middle (4–6), and one high (7–9) digit. Watch a worked example, then try the idea in a puzzle.
Put it into practice
Low · middle · high
An entropic line sorts Sudoku digits into three groups: low, middle and high.
1–3 · 4–6 · 7–9
Low means one to three. Middle means four to six. High means seven to nine. Any three neighbouring line cells must include one from each group.
The next cell is low
These three are low, middle, high: two, five, eight. Slide one cell along. Five and eight already cover middle and high, so the new cell must be low.
One or three
Low means one, two or three. Two is already in this row, so the new cell is one or three. We know its group, even before we know its digit.
Read the transcript
An entropic line sorts Sudoku digits into three groups: low, middle and high. Low means one to three. Middle means four to six. High means seven to nine. Any three neighbouring line cells must include one from each group. These three are low, middle, high: two, five, eight. Slide one cell along. Five and eight already cover middle and high, so the new cell must be low. Low means one, two or three. Two is already in this row, so the new cell is one or three. We know its group, even before we know its digit.
