I had an enjoyable time, but there's a few gripes I have with the game. I really like the pixel art and art style, and the concepts for each boss fights are pretty creative.
In theory, the revolver mechanic, with three different colored bullets with different effects that can pass through color-coded objects, works, but in practice there are many situations which (unless I'm missing something and you can switch bullets manually) it's much better to just spam the bullets to get the one you want rather than wait for the right opportunity. Good examples are when the clock boss gets a yellow shield, and you just have to keep firing until you randomly get a yellow bullet, and Bill's shield, where it's better to just fire all your bullets with no rhyme or reason than to wait for an opening.
Again, I had an enjoyable time, so I don't want to come across as to negative. Sorry if this offended you!