How to Play Thermometers: Rules, Strategy & Free Puzzles

Thermometers is a filling puzzle. The grid is covered with thermometers, each running from a round bulb to a flat tip. Mercury always fills from the bulb end and can never skip a gap, so a partly filled thermometer is filled continuously from its base. The numbers beside each row and column tell you how many cells in that line are filled.

• Skill: Constraint logic & counting
• ·
• Difficulty: Intermediate

How to play Thermometers

1. Fill from the bulb. Mercury starts at the round bulb and rises toward the tip without ever leaving a gap.
2. Match the row totals. The number beside a row is exactly how many filled cells it must contain.
3. Match the column totals. The number above a column is exactly how many filled cells it must contain.
4. Continuous only. A thermometer can be empty, partly filled from the bulb, or full — never filled in the middle only.

Thermometers strategy & tips

• A row whose clue equals its length is entirely filled; a clue of 0 is entirely empty.
• Because filling starts at the bulb, marking a cell empty forces every cell toward the tip empty too.
• Confirming a cell filled forces every cell back toward its bulb to be filled as well.

Thermometers FAQ

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