Love the concept & the gameplay, it's very fun.
Are you only supposed to be zooming in one place when using the scroll wheel?
It's a bit hard to see the things you are buying, wish there were an info box or something when you hover over them, with what type of defence they give, if they shoot or not etc.
The heartbeat sound should have some low-end taken away from it (EQ) , it becomes annoying for the ears after a while, because the "bass" in the beat is so low in frequency.
Started to stutter with heavy lag on level four, to the point it being unplayable. (running Brave Browser)