How to Play Mini Thermo Sudoku
Fill the 6x6 grid so that every row, every column, and every 2x3 box contains the digits 1 through 6 exactly once. Then add the thermometer rule.
- Thermometers increase: Digits along a thermometer must strictly increase from the round bulb to the tip. Equal digits are never allowed on a thermometer.
- The bulb is smallest: The large circle always holds the smallest digit on its thermometer.
- Tiny range, big clues: On a 6x6 board a five-cell thermometer can only be 1-2-3-4-5 or 2-3-4-5-6 — so long thermometers almost solve themselves.
- Conflict checking: A cell that breaks the increasing rule is ringed in amber immediately.
How this Mini Thermo Sudoku works
- Daily puzzle: One shared 6x6 puzzle per difficulty per day. The Daily Puzzle button brings you back to it.
- New Puzzle: Pulls a fresh grid from a bank of 150 mini thermometer puzzles (50 each of Easy, Medium, and Hard), every one with a single logical solution.
- Notes: Toggle Notes (or press N) to pencil in candidates 1–6.
- Keyboard play: Arrow keys move the selection, 1–6 place digits, Backspace erases.
Why start with the 6x6 mini?
The smaller grid keeps the thermometer logic front and center: with only six digits, each cell's position bounds are obvious, and you can finish a puzzle in a minute or two. Once the increasing rule feels natural, step up to the full 9x9 Thermo Sudoku. For the complete ruleset and techniques, see the Mini Thermo Sudoku guide.
Frequently Asked Questions
What is Mini Thermo Sudoku?
It is a 6x6 Thermometer Sudoku: fill each row, column, and 2x3 box with 1–6, and make every thermometer strictly increase from bulb to tip.
Why play the 6x6 instead of the 9x9?
The 6x6 is quicker and friendlier — the ideal way to learn how thermometers behave before moving up to the full grid.
What are the boxes in a 6x6 Sudoku?
A 6x6 Sudoku uses 2x3 boxes — two rows tall and three columns wide. Each of the six boxes holds 1 through 6 exactly once.
Can I play on my phone?
Absolutely. The board and pad are mobile-first. The free Sudoku - Brain Puzzles iOS app adds smart hints, daily streaks, iCloud sync, and 16 variants including Mini Arrow and Mega 16x16.