Great work on your first Godot project! I really like your theme interpretation, it's a fun twist to the otherwise simple gameplay, and makes it challenging.
It would have been nice to have a custom sprite for the player, maybe even animated/modulated to red/blue for temperature, but as a first time user you're excused for use our favourite placeholder, the Godot logo :) The temperature slider could also be styled to use a gradient from blue to red, or a thermometer sprite, and make its meaning more obvious.