Thermometer puzzle sizes and variants
Thermometer puzzles come in many forms. This page explains each variant you can play here and what makes each one harder or easier.
Straight vs curved thermometers
Straight thermometers are the classic form. Each one lies entirely in a single row or column, so it either sits along a line or crosses it once. That makes the squeeze and ceiling techniques easy to see.
Curved thermometers can turn at any cell. A single tube may cross a row twice or run through several columns, so one deduction can spread across the board. Curved puzzles look harder but often reward the flow-to-bulb technique with big chain reactions.
Grid sizes
| Size | Cells | Thermometers (approx.) | Level |
|---|---|---|---|
| 4×4 | 16 | 5–7 | Mini |
| 6×6 | 36 | 10–14 | Easy |
| 8×8 | 64 | 16–22 | Medium |
| 10×10 | 100 | 24–34 | Hard |
| 12×12 | 144 | 33–47 | Expert |
| 15×15 | 225 | 50–70 | Master |
Thermometer counts are typical ranges for our generator. Curved puzzles use fewer, longer thermometers than straight ones of the same size.
Pre-filled cells
Not every random layout of thermometers and clues has a single solution. To guarantee one, our generator may reveal a few cells in advance. These given cells appear on a tinted background and can't be changed. Small grids almost never need them; on 15×15 boards, a handful keep the puzzle fair and guess-free.
What makes a thermometer puzzle hard?
- Fewer extreme clues. Lines with clues of 0 or the full size are free starts. Hard puzzles have few of them.
- Long thermometers. Long tubes create more possible fill levels per thermometer.
- Crossing geometry. Curved tubes and many crossing thermometers make each line depend on others.
- Deduction depth. The longer the chain from one certain cell to the next, the harder the puzzle feels.
Daily and endless modes
Endless mode on the home page gives you a fresh random puzzle whenever you want one, each with a shareable ID. The daily puzzle is generated from the date, so everyone plays the same grid and can compare times.
Related logic puzzles
Thermometers share ideas with several other genres. Battleships (also called Bimaru) uses the same row and column counts. Nonograms share the idea of shading cells to match line clues. Tents and Star Battle also combine line counts with placement rules. If you enjoy thermometers, all of these will feel familiar.