Spiral Sudoku

Both thermometers are length 8, so the candidates are very limited.

There is a 34 pair, and a 78 pair along the thermometers.

No matter which cell contains 7, it will force a 3 into the 34 cell of its thermometer.

And the 3 would force a 4 to the other cell of 34 pair.

Therefore, the two thermometers must be:

• 1234567{8 or 9}

• {1 or 2}{2 or 3}456789

No matter what the green cells are, they must occupy 4 of 6 red cells.

Therefore, at least 2 of green cells must be in the 25 cage.

If the green cells are 1234, then, the maximum sum we can make for 25 cage is 3+4+8+9 = 24, which is not enough.

Therefore, the green cells must be: {1 or 2}{2 or 3}45.

And the 25 cage must be one of:

• 4+5+7+9

• 3+5+8+9

1 in box 9 can only be in row 7, therefore the lower thermometer must be 23456789.

5 and 6 on the thermometers make 5 and 6 in box 7 in the 23 cage.

7 in the green cell makes 7 in box 7 must be in red cells.

7 cannot be in 23 cage, otherwise we will need: 5 + 5 + 6 + 7 = 23.

7 must be in row 7 in box 7.

7 must be in the 25 cage in box 9

The 25 cage must be 4 + 5 + 7 + 9.

And after some deduction, the 23 cage must be 4 + 5 + 6 + 8.

The 123 in green cells make 123 in box 1 in the 15 cage, so the 15 cage must be 1239.

9 in box 1 and box 7 enforce the blue cell to be 9.

We can put the candidates in box 1, box 3, box 7 and box 9.

The green cells sum to 48.

The 48 cell must be 8, and the 18 cell must be 8.

And the "1~9" cell can only be 789.

The "1~8" cell can only be 78.

• The red cells are now a 34 pair.

The "1~6" cell can only be 456.

Now, the green cells must all be the maximum values they can be.

The yellow 46 cell cannot be 4 anymore. And yellow 78 cells sum to 15.

For the red cells, the 12348 and 12568 cells must have values greater than or equal to 5.

The 12348 cell now must be 8, and we can resolve yellow 78 cells.

The 12568 cell must be 5. And the other two red cells are determined now.

The green cells have to sum to 33, so the 123 and 169 cell must sum to 8.

The only combination that works is 2 + 6.

Now we have used all non-basic sudoku rules.

Rest of the puzzle can be solved by basic sudoku skills.