The UI can definitely be improved by reducing the amount of clutter on the screen.
You can do that by removing repetitive stats
(e.g. remove the thermometer stat and amount of enemies on screen stat).
You can also use visuals to help show stats instead of words or numbers
(E.g. replace the word "money" with an image of money.)
You can also hide stats and only show them when needed
(e.g. show the wave number when the wave starts, then hide it).
You probably should take everything here with a grain of salt, its just my opinion.
The gameplay is fun, especially the changing temperature mechanic. It makes for interesting gameplay as you have to manage when you want to switch the temperature to survive longer. A nice arcade game to play and pass the time.