Thermometers vs nonograms vs Battleships
Three popular logic puzzles put their clues outside the grid, beside each row and column. They share a family resemblance, but each clue means something different, and that changes how you solve.
Part of the complete guide to thermometer puzzles · guide 2 of 7
At a glance
| Thermometers | Nonograms | Battleships | |
|---|---|---|---|
| Clue beside a line | How many cells are filled | Lengths of each filled run, in order | How many cells hold ship parts |
| Structure inside the grid | Thermometers covering every cell | None (blank grid) | A list of ships to place, sometimes a few revealed cells |
| The extra rule | Fill from the bulb, no gaps | Runs appear in the given order, separated by gaps | Ships are straight and may not touch, even diagonally |
| Result | A filled grid | Often a picture | A hidden fleet revealed |
| Rules to learn | 3 | 2–3 | 3–4 |
Counts vs runs: what the clues tell you
In Thermometers and Battleships, a clue of 3 means three filled cells anywhere in the line. In a nonogram, a clue of "3" means one unbroken block of three, and "1 2" means a single cell, then a gap, then a block of two, in that order. Nonogram clues carry more information per line, which is why nonograms can work on a blank grid. Thermometer puzzles make up for having plain counts by putting structure inside the grid: the thermometers.
The overlap idea in all three
The most famous nonogram technique is the overlap: slide a block as far left as possible, then as far right, and any cells covered both times must be filled. Thermometers have the same move in a different form: a thermometer lying along a line with clue c in a grid of size n has at least L + c − n certain cells (see first moves). Battleships solvers use it too: a 4-cell ship in a 5-cell gap always covers the middle three cells.
Where the logic differs
- Thermometers are about bounds: the least and most each thermometer can put into a line (the squeeze and the ceiling; the reason it works is in the math guide). The fill order means one decided cell spreads along its whole tube.
- Nonograms are about positions of runs: where each block can start and end, and which blocks a filled cell could belong to.
- Battleships is about the fleet: which ship can go where, plus the no-touching rule that clears the cells around each placed ship.
Which should you try first?
If you already enjoy one of these, the others are a short step away. Thermometer puzzles are the quickest to learn, because there is no fleet to remember and no run order to track, and they scale smoothly from a 4×4 warm-up to a 15×15 marathon. Start with how to play, then a 6×6 puzzle. If you teach, see thermometer puzzles for classrooms. For a comparison with digit puzzles, see Thermometers vs Thermo-Sudoku.
Questions
Which of the three is easiest to learn?
Are thermometer puzzles like Picross?
Try a thermometer puzzle
If you know nonograms or Battleships, you are already halfway there.