How can I adjust video size for different devices?

[GenuineEssiac]

Hi, 

On a page like this, on desktop the testimonial video is showing up as whole screen, and I prefer it to be smaller on desktop, but whole screen on mobile. Is there a way to do that?

https://genuineessiac.com/pages/see-how-rene-caisse-a-canadian-nurse-brought-essiac-tea-into-the-mai...