In Thermometers Puzzle, you do not choose which end is the bulb: use the arrow keys to select the fixed bulb or tip, then press Space to set that thermometer’s continuous bulb-first fluid level.
The puzzle uses one fixed 4 × 4 grid divided into eight two-cell thermometers. Each path has one bulb followed by one tip, and every grid cell belongs to exactly one thermometer, so there are no overlapping paths to interpret.
Your real choice is how far the fluid should extend. A thermometer can be empty, filled through the bulb cell only, or filled from the bulb through the tip. Choosing the right segment lets you set that level directly.
What bulb selection actually controls
Each thermometer has a fixed bulb and a fixed tip; neither end can be swapped to make a clue easier to satisfy. Because every path contains two cells, its only legal levels are 0, 1, and 2. Level 0 leaves the path empty, level 1 fills the bulb cell, and level 2 fills both cells continuously from bulb to tip.
That is why selecting the bulb and selecting the tip produce different results. The bulb is the required starting point for all fluid, while the tip represents the far end of the two-cell path. The interface also announces each cell’s position and whether it is a bulb or tip, which helps when the visual roles are not immediately clear.
These mechanics follow the bulb-first, continuous-fill principle documented by the maintained Puzzle Thermometers rules reference and independently cross-checked by Puzzle Genius’s Thermometers guide.
Match the level to the selected segment
Move the selection with the arrow keys. Press Space on the segment that should be the end of the fluid. If the selected bulb is already filled, Space lowers the thermometer to level 0; if the selected tip is already filled, it lowers the thermometer to level 1.
| Selected segment and current state | Result after pressing Space | Resulting level |
|---|---|---|
| Unfilled bulb | Fill through the bulb | Level 1: bulb cell only |
| Unfilled tip | Fill through the tip | Level 2: bulb and tip filled |
| Filled tip | Lower to the segment immediately before the tip | Level 1: tip becomes empty |
| Filled bulb | Clear the entire path | Level 0: entire path becomes empty |
To raise a bulb-only thermometer to full, select its still-empty tip and press Space. To reduce a full thermometer, select its filled tip and press Space; the tip empties while the bulb remains filled. To clear a bulb-only thermometer, select its filled bulb and press Space. These controls preserve continuity because validation rebuilds the filled cells from the declared path and level after every action.
Use exact line clues to plan the levels
The row clues from top to bottom are 3, 2, 3, and 1. The column clues from left to right are 2, 2, 2, and 3. Each clue counts filled cells in that line, not the number of thermometers touching it. A bulb-only thermometer contributes one filled cell to its row and column. A full horizontal thermometer contributes two cells to one row and one cell to each of two columns; a full vertical thermometer contributes one cell to each of two rows and two cells to one column.
Use the clues before committing to a level. Start with lines that already have the required total and avoid adding fluid there unless you also reduce another path in the same line. For an underfilled line, identify which neighboring paths could legally accept more fluid without making their other row or column exceed its clue.
If a row or column exceeds its clue, the board reports a contradiction so you can revise the responsible level. The warning does not change the basic rule that a legal level can be empty, bulb-only, or full. An underfilled line remains playable because another legal increase may still complete it.
Optional empty marks should not be confused with deductions supplied by the game. Press Enter only on an unfilled cell to add or remove a private note. Notes can help you remember why a cell should stay empty, but only fluid levels determine completion, validation, and score.
Set the thermometers step by step
Use this keyboard workflow whenever you need to choose a bulb or change a thermometer’s level:
- Open the fixed board. Launch Thermometers Puzzle and check that you can see the bulb and tip on each two-cell path.
- Read the line clues first. Note the row totals of 3, 2, 3, and 1 and the column totals of 2, 2, 2, and 3 before changing any level.
- Move to a known cell. Use the arrow keys until the selection reaches the bulb or tip you want to adjust. The selected cell’s role is announced by the interface.
- Fill only the bulb cell when needed. If the bulb is unfilled, select it and press Space to set the thermometer to level 1 without adding fluid at the tip. If the bulb is already filled, press Space to clear the path to level 0.
- Fill the entire path when needed. If the tip is unfilled, select it and press Space to set level 2, filling the bulb first and then the adjacent tip. If the tip is already filled, press Space to lower the level to 1.
- Correct an excessive level. To lower a full thermometer, select its filled tip and press Space to set level 1. To clear a bulb-only thermometer, select its filled bulb and press Space to set level 0.
- Record an exclusion if useful. Select an unfilled cell and press Enter to place an empty mark. This is optional and does not constrain the answer.
- Check every affected line. After each adjustment, review both the row and column containing the thermometer. Continue until all eight line totals match exactly.
The fixed board’s published solution
The product’s verified solution uses the following ordered level sequence. The path numbers describe the official eight-path data, not a new control or setting that must be entered.
| Ordered path | Disclosed level | Fill pattern |
|---|---|---|
| 1 | 2 | Full from bulb to tip |
| 2 | 1 | Only the bulb cell filled |
| 3 | 0 | Empty |
| 4 | 2 | Full from bulb to tip |
| 5 | 1 | Only the bulb cell filled |
| 6 | 2 | Full from bulb to tip |
| 7 | 1 | Only the bulb cell filled |
| 8 | 0 | Empty |
The disclosed keyboard completion uses cells 1, 3, 6, 9, 11, and 12 with six Space actions. Those actions set the six nonzero thermometer levels, while the remaining two paths stay empty.
Scoring uses max(0, 1,000 − 10 × level actions). For the six-action completion, 1,000 − (10 × 6) = 940, matching the disclosed clean-solve score. Empty-note actions do not alter that level-action calculation.
This route applies only to this fixed board. It is not a general answer for a different thermometer layout, because the bulbs, tips, clues, and valid level placements are specific to this puzzle.
Input options and useful limits
The keyboard gives the most direct control: arrows choose a bulb or tip, Space changes the fluid level, and Enter manages an optional note on an unfilled cell. Mouse and touch users can click to set a level and use the context-menu gesture for an empty mark.
All levels must be whole numbers from zero through the length of the path. A negative level, an invalid level count, or a level extending past the tip is rejected. Because every stored level fills from the bulb toward the tip, the puzzle cannot contain a floating tip or a gap behind the fluid.
Most importantly, there is no separate “correct bulb” choice hidden in the interface. The bulbs are fixed, clues count filled cells, and your task is to choose a legal segment and then set a level that makes every row and column total exact.
For a deeper look, see Can I Solve Water Flow Puzzle with a Keyboard?.
For a deeper look, see Easy Water Sort Puzzle Puzzles: A Beginner Move Guide.