*,
*::after,
*::before {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
hr {
  margin-block: 10px;
  border: 1px solid red;
}
ul {
  list-style: none;
}

/*
Specificity
! ........... id ........ class ....... tag
0 ........... 0 ........... 0 .......... 1
*/

:where(header) {
  width: 1000px;
  margin-inline: auto;
  padding: 20px;
}
:where(main) {
  width: 1000px;
  margin-inline: auto;
}
header:is(.my-header) {
  border: 2px solid red;
  margin-bottom: 20px;
}

/* header :is(h1, h2, p) {
  color: red;
  line-height: 1.7;
} */
/* header :is(.bold) {
  font-weight: bold;
} */
:is(header, main) h3,
p {
  color: black;
}

:where(header, main) h3,
p {
  color: blue;
}

main:has(h3) {
  border: 2px solid green;
}
.list li:has(+ li) {
  border-bottom: 1px solid black;
}
p:not(:has(span)) {
  color: green;
  font-size: 18px;
}

a:is(:hover, :focus) {
  color: red;
}

.sibling li + li {
  background-color: green;
}

.has-nav a {
  font-weight: 700;
  text-decoration: none;
  text-transform: uppercase;
  color: blueviolet;
  transition: all 0.3s ease-in-out;
}

.has-nav a:hover {
  color: #ff7a18;
}
.has-nav:has(a:hover) a:not(:hover) {
  opacity: 0.3;
}