<select id="repeatSelect" name="repeat" class="repeat-type">
  <option value="repeat">repeat</option>
  <option value="repeat-x">repeat-x</option>
  <option value="repeat-y">repeat-y</option>
  <option value="no-repeat">no-repeat</option>
  <option value="round">round</option>
  <option value="space">space</option>
  <option value="round no-repeat">round no-repea</option>
  <option value="no-repeat space">no-repeat space</option>
</select>

:root {
  &:has(select [value="repeat"]:checked) { --repeat: repeat; }
  &:has(select [value="repeat-x"]:checked) { --repeat: repeat-x; }
  &:has(select [value="repeat-y"]:checked) { --repeat: repeat-y; }
  &:has(select [value="no-repeat"]:checked) { --repeat: no-repeat; }
  &:has(select [value="round"]:checked) { --repeat: round; }
  &:has(select [value="space"]:checked) { --repeat: space; }
  &:has(select [value="round no-repeat"]:checked) { --repeat: round no-repeat; }
  &:has(select [value="no-repeat spacee"]:checked) { --repeat: no-repeat space; }
}

* {
  box-sizing: border-box;
  margin: 0 auto;
}

body {
  background-image: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/308367/star.svg);
  background-repeat: var(--repeat);
  display: grid;
  height: 100dvh;
  align-items: center;
}

select {
  background: #fff;
  font-size: 30px;
  margin-block-start: 1rem;
  padding: 1rem;
}