chromium/ash/webui/personalization_app/resources/js/wallpaper/wallpaper_fullscreen_element.html

<style>
  #container {
    background-color: transparent;
    height: 100%;
    pointer-events: auto;
    position: relative;
    width: 100%;
  }

  #container::backdrop {
    background: transparent;
    opacity: 0;
  }

  #exit {
    left: 20px;
    position: absolute;
    top: 20px;
  }

  #confirm {
    position: absolute;
    right: 20px;
    top: 20px;
  }

  #layoutButtons {
    backdrop-filter: blur(6px);
    /* Weird css hack to set multiple background colors stacked on top of each
       other. It is possible to set multiple backgrounds, but normally one solid
       color. */
    background: linear-gradient(0deg, rgba(255, 255, 255, 0.08),
      rgba(255, 255, 255, 0.08)),
      rgba(32, 33, 36, 0.8);
    border-radius: 16px;
    column-gap: 8px;
    display: grid;
    grid-template-columns: 1fr 1fr;
    left: 50%;
    position: absolute;
    top: 20px;
    transform: translateX(-50%);
  }

  #layoutButtons .fullscreen-button {
    backdrop-filter: none;
    background: none;
    padding: 6px 24px;
    width: 100%;
  }

  #layoutButtons .fullscreen-button:hover {
    background: rgba(var(--google-blue-300-rgb), 0.08);
  }

  #layoutButtons .fullscreen-button[aria-pressed='true'] {
    background: var(--cros-sys-primary-dark, --google-blue-300);
    color: var(--google-grey-900);
  }

  img {
    left: 50%;
    position: absolute;
    top: 50%;
    transform: translate(-50%, -50%);
  }

  /* Not using semantic colors - fixed for dark and light mode. */
  .fullscreen-button {
    align-items: center;
    backdrop-filter: blur(6px);
    background: linear-gradient(0deg, rgba(255, 255, 255, 0.08),
      rgba(255, 255, 255, 0.08)),
      rgba(var(--google-grey-900-rgb), 0.8);
    border: none;
    border-radius: 16px;
    color: var(--google-grey-200);
    display: flex;
    height: 32px;
    justify-content: center;
    min-width: max-content;
    padding: 6px 16px;
  }

  .fullscreen-button:hover {
    background: linear-gradient(0deg, rgba(var(--google-blue-300-rgb), 0.08),
      rgba(var(--google-blue-300-rgb), 0.08)),
      rgba(var(--google-grey-900-rgb), 0.8);
  }

  .fullscreen-button iron-icon {
    flex: 0 0 auto;
    --iron-icon-height: 20px;
    --iron-icon-width: 20px;
  }

  .fullscreen-button span {
    margin-inline-start: 8px;
  }

</style>
<div id="container" hidden$="[[!showContainer_]]">
  <cr-button class="fullscreen-button" on-click="onClickExit_" id="exit"
      aria-label="$i18n{ariaLabelExitFullscreen}">
    <iron-icon icon="personalization:exit_fullscreen"></iron-icon>
    <span>$i18n{exitFullscreen}</span>
  </cr-button>
  <template is="dom-if" if="[[showLayoutOptions_]]">
    <div id="layoutButtons">
      <cr-button class="fullscreen-button" on-click="onClickLayout_"
          data-layout="FILL"
          aria-pressed$="[[getLayoutAriaPressed_(selectedLayout_, 'FILL')]]">
        <iron-icon icon="personalization:layout_fill"></iron-icon>
        <span>$i18n{fill}</span>
      </cr-button>
      <cr-button class="fullscreen-button" on-click="onClickLayout_"
          data-layout="CENTER"
          aria-pressed$="[[getLayoutAriaPressed_(selectedLayout_, 'CENTER')]]">
        <iron-icon icon="personalization:layout_center"></iron-icon>
        <span>$i18n{center}</span>
      </cr-button>
    </div>
  </template>
  <cr-button class="fullscreen-button" on-click="onClickConfirm_" id="confirm">
    <iron-icon icon="personalization:confirm_selection"></iron-icon>
    <span>$i18n{setAsWallpaper}</span>
  </cr-button>
</div>