Apple's Liquid Glass software design language is bringing a new look to your Mac. Some of it you'll likely spot right away -- like the revamped menu bar, which will have a completely clear background.

If you’re running Leopard, hit Command + Shift + 4 and then the space bar, and you’ll see an icon of a camera that harks back to Steve Jobs’s days at NeXT. The decades-old icon is one of the last ...