Played the whole thing, liked it plenty :) The sense of progression and pacing is quite well done! Here are some suggestions for improvement tho:
The tutorial is just hand-holdy and restrictive enough to be irritating, although it is thankfully pretty short. I think even just the ability to click buttons other than the tutorial-mandated ones would make it less annoying.
An option to change the UI or text scale would be nice, since some of the text is really small on my laptop screen (especially the text in the settings, which is counterintuitive).
A toggle to hide maxed upgrades.
The option to click and hold for a few things like charging, spawing numbers, or dealing damage to reduce hand strain.
On that note, the amount of clicking necessary is pretty strenous in general (at least on mouse). It was fine for this demo, but I definitely would not be able to play a full game if spamclicking stays a regular requirement to progress.
Keep it up!