Adding a border around a video

Is there a way to add a border around a video using CL? I made a video and uploaded it to the Desmos Activity Builder, but when I made the video, it was on a white background. It looks like an image unless you scroll way down to get the play button. I’m worried students won’t realize it’s a video since I thought it was an image at first too!

I don’t believe there is an option for this. You can do it for images, but the videos do get a bit darker on the lower half to emphasize the play button.