Daily Thermo Sudoku
The one extra rule
Normal sudoku rules, plus this: along every thermometer the digits must strictly increase from the round bulb to the tip.
That is the whole game. A nine-cell thermometer can only be 1 to 9 in order, and even a short one rules out far more than it looks.
Controls
Click a cell and type a digit, or use the pad. Space toggles pencil marks. Arrow keys move.
Your progress is saved in this browser as you go, so you can close the tab and pick the same puzzle up later the same day. Nothing is uploaded and there is no account.
Why a Thermometer Is Worth More Than a Given Digit
A given digit tells you about one cell. A thermometer tells you about every cell it touches, in both directions. The bulb cannot be 9, the tip cannot be 1, and the cell above a 4 is at least a 5. Work from both ends and the squeeze does most of your job for you.
That is why most of these puzzles start with very few digits, and a handful start with none at all. Every one of them can be solved by pure logic, with no guessing anywhere. That is not a claim, it is a condition of being here: each puzzle was generated and then proved solvable by a solver that is only allowed to use techniques a person can use. Anything that needed a guess was thrown away.
More to Play
There is 2048 if you want something faster, and the puzzle tools if you would rather solve a real object: a burr solver, a polycube box fitter and more. The puzzles themselves are in mechanical puzzles.