[lioeters]

Looking in the raw Markdown file, I see the shadowing is not done with CSS, it's included in the PNG image with transparency.

[bensadeh]

This actually comes out of the box for the system screenshot tool in macOS (Cmd + Shift + 4 and then Space to select window). The screenshot of the window will then have this shadowing around it.

[lioeters]

Ooh right, I remember seeing that by chance before. Thanks for the clarification.