Question 1

What is Thermo Sudoku?

Accepted Answer

Each thermometer runs from its bulb, the circle, to its tip. The digits must rise strictly along it, every step larger than the last. Temperature never falls on these lines, and neither may your digits.

Question 2

How do you solve Thermo Sudoku?

Accepted Answer

A three-cell thermometer on a 4 by 4 grid can only read 1, 2, 3 or 2, 3, 4. There is very little weather to speak of. The bulb always holds the smallest digit on its line. Start there and the rest follows, as causes tend to. A four-cell thermometer here must read 1, 2, 3, 4 exactly. One observation, and the whole line is solved. Enjoy it; they are not all this generous. A four-cell thermometer needs four rising digits drawn from 1 to 6. Count how many starting values could possibly survive the climb. The bulb cannot be large. A three-cell line starting at 5 would need a 6 and then a 7, and 7 does not exist here, so the bulb is at most 4. Where a thermometer crosses a box boundary, the rising sequence squeezes both boxes at once. Two constraints for the price of one line. When two thermometers share a row, apply both climbs together. The candidates collapse far faster than either line manages alone.

Thermo Sudoku

How do you solve Thermo Sudoku?

Start on a 4 by 4 grid

Then try a 6 by 6 grid

What does Thermo Sudoku look like?

Where can you play Thermo Sudoku?