Is there a sandbox...
I don't know - you'd have to poke around the site. They do have a number of other simulations linked at the bottom.
I thought it was interesting as an illustration, even if it doesn't represent a mix of preferences.
Also I find it offensive to suggest that I'm missing out on a different skin colour in my life. I was not aware that being brown gave you a unique quality that I couldn't get any other way.
Interesting. I didn't associate it with skin color or race exclusively, but anything that could lead to bias. Religion, specific ethnicity (Irish vs. Scottish vs. Italian), etc. It's not until you get to the very end that they even mention race at all, and that's mostly to point at the research that the site was based on. Within that text, they also point to work that involves male-female distinctions and "bad apples" having an outsized impact on communities.