# Thermometer Puzzle

> ThermometerPuzzle.com is a free website for playing thermometer logic puzzles (also called "Thermometers" or "Thermo puzzles") online. Every puzzle is computer-verified to have exactly one solution. It offers six grid sizes (4×4 to 15×15), straight and curved thermometers, a daily puzzle, smart hints, printable puzzles with answer keys, and in-depth guides.

## Rules (summary)
- The grid is divided into thermometers; each has a round bulb at one end and a flat tip at the other.
- Fill some thermometers with mercury. Mercury always starts at the bulb and is continuous toward the tip (no gaps). A thermometer may be empty, partly filled, or full.
- The number beside each row and above each column is the exact count of mercury cells in that line.
- A puzzle is solved when every row and column matches its clue.

## Key solving techniques
- Empty and full lines: a clue of 0 makes the whole line air; a clue equal to the grid size makes it all mercury.
- Flow: a mercury cell implies every cell back to the bulb is mercury; an air cell implies every cell forward to the tip is air.
- Squeeze (minimum fill): if other thermometers in a line cannot supply the clue, the remainder is forced from the bulb end of one thermometer.
- Ceiling (maximum fill): a small clue caps how far a thermometer along that line can fill.
- Capacity: a thermometer crossing a line contributes at most one cell to it.

## Pages
- [Play online](https://thermometerpuzzle.com/): interactive game, all sizes and styles
- [Daily puzzle](https://thermometerpuzzle.com/daily/): one shared puzzle per size per day, with streaks
- [How to play](https://thermometerpuzzle.com/how-to-play/): rules, controls, and a step-by-step solved 4×4 example
- [Strategies](https://thermometerpuzzle.com/strategies/): 10 solving techniques with diagrams
- [Sizes & variants](https://thermometerpuzzle.com/variants/): straight vs curved, grid sizes, difficulty
- [Printable puzzles](https://thermometerpuzzle.com/printable/): print sheets with answer keys
- [Glossary](https://thermometerpuzzle.com/glossary/): definitions of bulb, tip, mercury, squeeze, ceiling and more
- [FAQ](https://thermometerpuzzle.com/faq/)
- Size pages: [4×4](https://thermometerpuzzle.com/4x4/), [6×6](https://thermometerpuzzle.com/6x6/), [8×8](https://thermometerpuzzle.com/8x8/), [10×10](https://thermometerpuzzle.com/10x10/), [12×12](https://thermometerpuzzle.com/12x12/), [15×15](https://thermometerpuzzle.com/15x15/), [Curved](https://thermometerpuzzle.com/curved/)

## Facts
- Cost: free, no account required
- Platforms: any modern web browser on desktop, tablet or phone
- Puzzle links: https://thermometerpuzzle.com/?size=10&style=curved&id=123456 opens a specific puzzle