I found this counter-intuitive as well, for the little it's worth. My intuition was "Wow, there's a lot of lines on this graph. I'll clear everything off and th

I found this counter-intuitive as well, for the little it's worth. My intuition was "Wow, there's a lot of lines on this graph. I'll clear everything off and then add things one at a time to see how they compare. Click, click, click wait, what happened there?" I get that it's just a demo though, not behaviour the end developer has to put in their app. It's a really nice set of demos overall. :)