HOW NOT TO USE BOX SHADOWS

Summary from the TLDR Web Dev newsletter

Box shadows in CSS can be used to create a variety of effects beyond simple drop shadows, such as layered shadows, rounded corners, and 3D-like effects. They can be combined and animated to create complex visuals, such as bouncing balls and simulated 3D objects. This article goes over how to and how not to use box shadows. Using box shadows for such advanced effects can be performance-intensive, especially when blurring or transparency is involved.