Each region is a snake. Each end of a thermometer is also an end of a snake region.
A snake is a one cell wide path of orthogonally connected cells that does not branch or contain a 2x2 block of cells.
A 9x9 example grid just to show valid snake regions
Note there are only 8 thermos in the grid. Unfortunately the 9th was stolen.
Play online
CtC
I would recommend using the pen tool to mark the thermo ends. If you are finding the thermos too distracting, try the second uncluttered link below to build the regions separately.
Region Builder
If you enjoyed this, please check out my other puzzles.
Solution code: Row 1
on 21. October 2023, 13:45 by marcmees
very nice. thanks
on 10. December 2022, 14:27 by Al Fresco
Thank you kjholt & SeveNateNine for the nice feedback.
on 10. December 2022, 10:10 by SeveNateNine
Top tier break-in!
on 10. December 2022, 01:40 by kjholt
Loved this! Got stuck in the middle and as soon as I figured it out it was smooth sailing from there. Very clever!