Yeah, probably related to the screen size issue. Forgot to test it on small monitors. There's a big "next slide" button on the bottom, but it gets cut off for smaller monitors.
You can sort of work around it by minimizing it using ctrl+-. But, yeah. I sorta screwed up by not getting it to work on smaller screens and mobile. Sincere apologies!
This isn't exactly a niche set-up I'm using. Having a fixed height is pretty much useless for anything you want people to use in a meaningful way.
If it's an art piece, then I guess it doesn't matter. I can't tell, because it's not usable.