Thanks for playing!
I'll address these issues one by one:
Restarting the game with buttons - The whole gameplay is done with only a keyboard, so it feels strange having to reach for my mouse to click 3 times just then go back to my keyboard while playing.
I was originally planning on having like, space, as a shortcut key for the buttons. However, I knew some people would be playing with controller - and I myself was playtesting with a controller. Godot only lets me assign one shortcut key to a button, so I decided to assign it to the controller - as the people who were playing with a keyboard most likely had a mouse handy with them, while the people who were playing with controller probably didnt want to keep switching between controller and mouse.
The bugs... - I think making them insta-kill you was a little overkill... Since then you have to start over from the beginning... and replaying a relatively easy part of the game just to try the bossfight again is not that inviting.
If I continue developing the game, then I will reduce virus enemy damage, since i'm getting many complaints for that. I was also originally planning on having some sort of save system, so it would save whether you reached boss or not, but I could not do that due to time limitations D:
Although it is nice that you made the hitboxes generous, it feels more like it is a bug... (Now that I read the comments I got to know that there is a focus ability...)
Yeah, I should have probably made the focus ability more clear |:
Thx for playing and for feedback!