The case notes
Count a same-class line against its row
All three cells on this isotropic line use one digit band. We do not yet know whether it is low, middle or high. Watch a worked example, then try the idea in a puzzle.
Put it into practice
One line · one band
All three cells on this isotropic line use one digit band. We do not yet know whether it is low, middle or high.
The line cannot be low
A full row contains only three low digits: one, two and three. One is already outside the line. Three more lows on the line would make four.
The line cannot be middle
Four is a middle digit outside the line. The same count rules out three middle digits on the line.
Line claims 7, 8, 9
That leaves the high band. The line’s three cells share a row, so they take seven, eight and nine in some order.
Outside cells are not high
Every high digit is spoken for. The cells outside the line lose seven, eight and nine as possibilities.
Read the transcript
All three cells on this isotropic line use one digit band. We do not yet know whether it is low, middle or high. A full row contains only three low digits: one, two and three. One is already outside the line. Three more lows on the line would make four. Four is a middle digit outside the line. The same count rules out three middle digits on the line. That leaves the high band. The line’s three cells share a row, so they take seven, eight and nine in some order. Every high digit is spoken for. The cells outside the line lose seven, eight and nine as possibilities.
