I love the upgrade system of getting different suits and such after each phase. I found the difficulty a bit too challenging considering how long the boss fight is. It felt like I wasn't doing much damage, but that seemed to just be that the boss floats just out of range of the spreadshot attack so it looked like I was hitting but in reality I was just shooting the area in front of it.
I really liked the spinning coin animation though, that was really cool. The upgrades also seemed to be very impactful!