Thank you for providing so much detailed feedback, it is highly appreciated!
The reception so far has been incredibly positive, and considering how little time I have spent developing so far, I hope with just a few updates the game will rival it's competition in terms of polish.
Indicating waves is something I have been thinking a lot about, and I have a few solutions in mind. Currently, I am leaning towards providing a form of difficulty indicator for the upcoming wave as well as a countdown timer during the pause period. This would also allow me to randomize the waves a bit to make replaying levels a bit less predictable.
Anyways, thanks again for the feedback, and let me know if you are able to fix the UI scaling issue in your game, I'd love to give it a fair review!