Code
Here, various nested <div> elements are implemented to form three interactive embedded Desmos graphs — one from Desmos Graphing Calculator, one from Desmos Geometry, and one from one of Desmos' newest tools, Desmos 3D. The code shown here is for the first of the three embedded graphs (the one from Desmos Graphing Calculator).
UI
On the homepage of Desmos, there are three interactive embedded Desmos graphs. (The screenshot shown here shows one of these three embedded graphs; to see a brief demonstration of all three, click on the screenshot.) These three embedded graphs are likely set up with a combination of HyperText Markup Language (HTML), Cascading Style Sheets (CSS), and JavaScript (JS).
UX
The three interactive embedded graphs most certainly enhance the User Experience (UX). They enhance the overall feel, aesthetic, and theme of the homepage.
Summary
Overall, Desmos has done a great job with their homepage. As far as I can see, there aren't any major problems therein.