Thermo Sudoku

Rules

A thermometer is a line with a bulb at one end. Digits must increase strictly from the bulb to the tip — never equal, never falling. The bulb is the smallest digit on the line, the tip the largest.

• Every thermometer increases strictly from bulb to tip.
• The bulb is always the lowest digit of the line; the tip the highest.
• Lines cross boxes freely — a thermometer is not a sudoku unit.
• Start at the bulb: it can never be 8 or 9, and the tip can never be 1 or 2.

Good to know

Ordinary sudoku rules still apply underneath the variant: every row, column and 3×3 box holds 1–9 exactly once. The extra rule sits on top and is usually what breaks the puzzle open.

More sudoku

All sudoku variants ↗

Or read how to play Sudoku ↗.