description Thermo-Sudoku Overview
Thermo-Sudoku is a variant of the traditional Sudoku puzzle that incorporates a constraint based on thermometer-shaped lines drawn on the grid. Along each thermometer line, digits must strictly increase in value starting from the unnumbered bulb end and moving toward the tip. Standard Sudoku rules still apply, meaning digits from 1 to 9 must appear exactly once in each row, column, and 3x3 box. The thermometer constraint eliminates the need for many pre-filled numbers, relying on the strict increasing sequence to create a unique solution.
insights Ranking position
Thermo-Sudoku ranks #8 of 93 in the Logic Puzzle ranking, behind Star Battle, ahead of Knights and Knaves.
help Thermo-Sudoku FAQ
What are the rules of Thermo-Sudoku?
In Thermo-Sudoku, standard Sudoku rules apply, meaning digits 1-9 cannot repeat in any row, column, or 3x3 box. The added constraint is that thermometer-shaped lines are drawn on the grid, and the digits along each thermometer must strictly increase starting from the bulb end to the tip.
Can numbers repeat on a thermometer in Thermo-Sudoku?
No, because the numbers must strictly increase from the bulb to the tip, no number can ever repeat on a single thermometer. This heavily restricts the possible placements for low and high numbers on the Sudoku grid.
Where did the Thermo-Sudoku puzzle variant originate?
The variant was heavily popularized by the puzzle website Cracking the Cryptic and its founders, Simon Anthony and Mark Goodliffe. It has since become a staple in modern digital puzzle solving competitions.
Do you need to use math to solve a Thermo-Sudoku?
No, Thermo-Sudoku relies entirely on pure logic rather than arithmetic. You simply use the concept of numerical ordering—where the bulb is the lowest number and the tip is the highest—to deduce where numbers belong on the board.
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