Thermometers Solving Tips
Thermometers is solved by two chains of logic that run in opposite directions along each tube. New here? Read the rules first.
1. Zeros and full lines
A row count of 0: every square in that row is empty, and so is every square beyond it in its thermometer. A count equal to the row length: every square is filled, and so is every square between it and its bulb.
2. Filled pulls toward the bulb
If a square is filled, all squares from the bulb to it are filled too. Count those extra fills against their rows and columns.
3. Empty pushes outward
If a square is empty, everything beyond it toward the tip is empty as well. That removes squares from the lines they cross, which often makes a count reachable only one way.
4. Compare need and room
For each line, compare the count still needed with the squares still undecided. Equal means all of them fill; a need of 0 means all of them empty.
5. Use the long thermometers
A long thermometer touches many lines. Its level is pinned down quickly by whichever of those lines is tightest; start there.
Frequently asked questions
What's the first thing to look for?
Rows or columns with a count of 0 or equal to their length. A 0 empties every thermometer crossing that line from that square outward; a full count fills every square in the line and everything between those squares and their bulbs.
Last updated 2026-10-21