A single box-shadow declaration produces a shadow that looks functional but rarely looks polished. If you've ever wondered why shadows in high-quality design systems look better than the ones you write from scratch, the answer is almost always multiple layers. Understanding how CSS handles layered shadows changes how you approach the property entirely.

The Basic Syntax

The box-shadow shorthand takes up to six values:

box-shadow : offset-x offset-y blur-radius spread-radius color ;

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With an optional inset keyword at the front to flip the shadow inside the element:

box-shadow : inset 0 2 px 4 px rgba ( 0 , 0 , 0 , 0 . 1 );

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The only required values are offset-x and offset-y.…