I had a good time playing this. The way the boss drops coins and the occasional bill is very satisfying. The boss does not do too many crazy attacks so I got to enjoy rolling the slots a bunch. All of the effects in the slot machines were fun to see. I definitely did not like inverted controls or distortion, but it is still a cool feature.
I think the only way I managed to win was by switching health with the boss. The bullets don't feel impactful enough even with a damage upgrade. The 5 slot machine is kind of overwhelming compared to the 3 slot machine. Maybe if the 3 slot machine could give you 3 upgrades instead of the one, there would be more consistency.