CSS is Aspect-Oriented Programming

A group of CSS rules is essentially a function. (They even use the same curly-brace and semicolon syntax.) …

form h1 {
font-size: 15px;
color: blue;
}

Suddenly, all h1 tags inside forms have this behavior, even though none of them reference this “function”.

Aspect-oriented programming is the most misunderstood programming paradigm. But fundamentally, the reason it exists is the same reason CSS exists — to better separate concerns in your code.