Extreme technique · Technique Academy

Simple Coloring

Simple Coloring follows one digit through a chain of cells linked in pairs, each pair being the only two places for that digit in some unit, and paints alternate cells in two colours. Exactly one colour holds the digit, though you do not yet know which.

Professor Cryptic, the owl who teaches in the app
Professor Cryptic is thinking

The reasoning

Why does the Simple Coloring work?

If two cells of the same colour see each other, that colour is false and the other is true. A cell outside the chain that sees both colours cannot hold the digit either, because one of them must.

A worked example

What does the Simple Coloring look like on a real board?

Simple Coloring worked exampleA sudoku board with pencil marks. The Simple Coloring uses R2C1, R2C4, R7C1, R1C3, R7C4, R3C5, R8C2, R4C3, R3C7, R6C5, R4C2, R6C6 and digit 6 (a colour trap). The move strikes candidate 6 in R8C7.156729834674667496753812283467167979586767145239415329676783928676745451693456821597567891467462379215734659846
The move strikes candidate 6 in R8C7. Digit 6, a colour trap.
  • Cells that form the pattern
  • Cells that lose a candidate
  • Struck digit: ruled out

Make it stick

How can you practise the Simple Coloring?

The Technique Academy in Cryptic gives every technique its own lesson and 5 practice boards that need exactly this move.

Get it onGoogle PlayPlay Cryptic on the web

Further reading: HoDoKu's page on this family of techniques.

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