The transitions are good enough, the menus are not so.
(I hate to say it this way, but they menus are a little ugly)
The music is pretty good, but it doesn't fit with the aesthetic very much.
The font is hard to read and the instruction for the boss are not really necessary, they are not things that are figuring it out for yourself
I did try to shoot the portal for a while before realising what it was, but it was mostly because in most of the other games the boss just appear without too much introduction (also the portal doesn't move like a "classic "portal would
Making the boss vulnerable when the eyelid is close is a little weird following video game traditions until now, I has a little more sense to make the bosses vulnerable when the eye is open.
Having 3 entities for a boss that get angry when you defeat one of its pals is a cool idea but I was super methodical with the fight and super careful, to the point of having more than 50% of my health and having the 3 bosses with one hit of life left and even with all that preparation, at the moment of killing each eyeball I still got killed, and I have lots of health and I only needed to shoot every ball once to defeat them
The "Angry" mode is way too powerful
I didn't get to see other bosses because I tried to defeat the first one many times, but I got owned each time from the over powered state that he eyeballs enter