Logic Masters Deutschland e.V.

I've made a few thermo variants. All are standard thermo sudokus + an extra rule. Check out the others using the following link:

Thermo Variant Series puzzles

If you enjoy "Maximal Thermos" or would like more practice first, I invite you to look at the others with the same (or similar) constraint:

14. Maximal Thermos
19. Maximal Thermos 2
21. All Maximal Thermos are Given
23. Incomplete Maximal Thermos
26. Maximal Thermos 3: Stubs
31. All Maximal Thermos are Given 2
35. Maximal Thermos 4ever

Rules: Normal sudoku rules apply. Along thermometers, digits must increase from the bulb end.

Variant: The thermos in the grid are maximal thermos. This means two things:
(1) the digit in the bulb equals the length of the thermo
(2) the tip of the thermo cannot be extended by a king's move to a non-thermo cell to create a larger thermo.

For example, if r4c3 = 7 then r3c2, r4c2, r5c3, r5c4, and r4c4 cannot equal 8 or 9.

One extra rule: The non-thermo cells cannot form a maximal thermo of length 3 or larger.

Hint 1 for the middle of the solve (highlight to read):

After some sudoku and variant logic, you should be able to place the 4 in box 1 and the 4 in box 9 using the negative constraint.

Hint 2 for the middle of the solve (highlight to read):

Look at the 3 in box 8, the cells surrounding it are very restricted by the negative constraint! You may want to pencilmark them.

Spoiler for Hint 2 (highlight to read):

You should be able to prove that r9c6 must be a 2, 7 or 8. Then look at what happens with the negative constraint with the 4 in box 3 and 9 in box 2 if r9c6 was a 2.

Of course, there are other ways to go about it, this is just one way!

F-puzzles link: https://f-puzzles.com/?id=yykqpgao
CTC link: https://tinyurl.com/2y445jw8