CSS Light/Dark Theme Toggle

body:has(input[type="checkbox"]:checked) {
  background: blue;
  --primary-color: white;
}
body:has(input[type="checkbox"]:checked) form { 
  border: 4px solid white;
}
body:has(input[type="checkbox"]:checked) form:has(:focus-visible) {
  background: navy;
}
body:has(input[type="checkbox"]:checked) input:focus-visible {
  outline: 4px solid lightsalmon;
}