Thermometers
Fill thermometers from the bulb up
Thermometers is a filling logic puzzle with a satisfyingly physical metaphor. The grid contains thermometer shapes, each with a bulb at one end. Mercury fills from the bulb toward the tip — you can fill a thermometer partially or completely, but filled cells must be contiguous starting from the bulb. Row and column numbers tell you the total count of filled cells in each line. The constraint that filling must start from the bulb gives Thermometers a unique directional quality absent from most grid puzzles.
How to Play Thermometers
Thermometer Shapes
The grid contains thermometers of various lengths and orientations. Each has a round bulb at one end and extends in a direction.
Fill from the Bulb
Mercury fills continuously from the bulb. You can't fill the tip without filling everything between it and the bulb first.
Partial or Full
Thermometers can be completely empty, partially filled, or completely full. But filled cells must be contiguous from the bulb.
Row Clues
Numbers on the left tell you exactly how many filled cells are in that row.
Column Clues
Numbers on the top tell you exactly how many filled cells are in that column.
Count Matching
Your solution is correct when every row and column count matches the given numbers, and all thermometers are validly filled.
Strategy & Solving Tips
Thermometers solving combines counting logic with the directional fill constraint. These techniques form the core of efficient solving.
- A row or column with count 0 means every thermometer cell in that line is empty — this cascades since empty cells force earlier cells in those thermometers to also be empty... wait, the opposite: if a cell is empty, all cells further from the bulb must also be empty
- If filling a thermometer cell is required to meet a row/column count, all cells between it and the bulb must also be filled
- A full row/column (count equals total thermometer cells in that line) means every thermometer cell there is filled
- Long thermometers spanning many rows/columns are most constrained and should be analyzed first
- If a thermometer's bulb cell is in a row with count 0, the entire thermometer is empty
- Track minimum and maximum possible fill levels for each thermometer based on its row and column constraints
Thermometers FAQ
Can a thermometer be completely empty?
Yes. If the row and column counts don't require any of its cells to be filled, a thermometer can remain entirely empty.
Do thermometers only go vertically?
No. Thermometers can be horizontal, vertical, or even bent in some variants. The direction from bulb to tip is what matters for the fill order.
What if two thermometers share a row?
The row count applies to the total filled cells across all thermometers in that row. You must distribute the count among the thermometers while respecting each one's fill-from-bulb rule.
Can I skip cells when filling?
No. Mercury fills continuously from the bulb. If the third cell from the bulb is filled, the first and second must be filled too. Gaps are not allowed.
Ready to Play Thermometers?
Feel the mercury rise in Thermometers — the directional fill puzzle where every count and every bulb leads you to the exact right temperature.