Sorry, yes I did define an extension for UIColor that I forgot to mention! And the thumb is supposed to be able to go outside of the slider. I added a comment with the info! Also, by "scrubbing" I want to mimic the behavior in videos or podcasts where you can change the scrubbing rate / make the slider values change slower so you can select it with more precision.

It works now, tysm!!!

Ohhh, I see. Does that mean I need to create a view controller for the modifier as well?

That's annoying. Mine ended up being a style error that the Swift Playgrounds compiler choked on. Maybe yours is a similar problem? Also, just a heads up, we're not allowed to use Playground Books for the Swift Student Challenge this year :)