Yeah originally integrate only undid differentiate and wasn't a win condition. When I updated last week it I decided to add more levels going the other way with integrate. I realised it was much easier so I made it so you had to do it once more than differentiate. It might have been a mistake to let you do something that just lets you avoid the main joke but I also thought it was unsatisfyingly asymmetric before.
In 2017 I entered a contest on /r/Unitale to create an Undertale battle with the worst possible control scheme. I won. I have dug it out, updated it a little bit, and put it on Itch for all to "enjoy"
cute_spider_ni_srsly wrote
This boss is much easier to integrate rather than derive.
Also Tangerine lol