CodePen.scss

.simulated-select {
  --select-height: 2rem;
  --max-items: 5;
  --selected-background: #bfd4ed;
  --selected-color: #000;
  position: relative;
  position: sticky;
  inset: 0;
  isolation: isolate;
  height: var(--select-height);
  width: fit-content;

  .simulated-select-options-end {
    /* to give the illusion that the dropdown is focused: */
    position: absolute;
    left: 0;
    top: 0;
    height: 100%;
    width: 100%;
    border-radius: 0.25rem;
    z-index: -1;
    pointer-events: none;

    /* so no need to make visually hidden: */
    // position: absolute;
    // overflow: hidden;
    // clip: rect(0 0 0 0);
    // height: 1px;
    // width: 1px;
    // margin: -1px;
    // padding: 0;
    // border: 0;
  }

  .simulated-select-options-wrapper {
    display: flex;
    flex-direction: column;
    // position: absolute; // disable position so option can go to top
    box-sizing: border-box;
    max-width: max-content;
    border-radius: 0.25rem;
    height: var(--select-height);
    max-height: calc(var(--max-items) * var(--select-height));

    > [role="option"] {
      box-sizing: border-box;
      height: var(--select-height);
      width: 100%;
      border-radius: 0;
      border: none;
      border-top: 1px solid #dee2e6;
      background: #fff;
      color: #0053b8;
      cursor: pointer;
      padding: 0.5rem;
      line-height: 1rem;
      margin-right: 2rem;
      text-align: left;
      white-space: nowrap;
      &:focus,
      &:hover,
      &[selected] {
        background: var(--selected-background);
        color: var(--selected-color);
        outline-offset: -2px;
      }
      &[selected] {
        font-weight: bold;
      }
    }
  }
}

.simulated-select-options-wrapper:not(:focus-within) {
  overflow: hidden;

  > [role="option"] {
    background: lightgrey;
    color: var(--selected-color);

    &[selected] {
      position: absolute;
      top: 0;
      background: revert;
      font-weight: revert;
    }
  }
}

.simulated-select-options-wrapper:focus,
.simulated-select-options-wrapper:focus-within {
  height: revert;
  box-shadow: rgb(0 0 0 / 50%) 0px 2px 4px 0px;
  overflow-x: hidden;
  overflow-y: auto;
}