chrome/browser/resources/welcome/ntp_background/nux_ntp_background.html

<style include="animations chooser-shared-css">
  :host {
    text-align: center;
  }

  #backgroundPreview {
    background-position: center center;
    background-repeat: no-repeat;
    background-size: cover;
    bottom: 0;
    left: 0;
    opacity: 0;
    position: fixed;
    right: 0;
    top: 0;
    transition: background 300ms, opacity 400ms;
  }

  #backgroundPreview.active {
    opacity: 1;
  }

  #backgroundPreview::before {
    /* Copied from browser/resources/local_ntp/custom_backgrounds.js */
    background-image: linear-gradient(rgba(0, 0, 0, 0), rgba(0, 0, 0, .3));
    /* Pseudo element needs some content (even an empty string) to be
     * displayed. */
    content: '';
    display: block;
    height: 100%;
    width: 100%;
  }

  .content {
    /* Put a non-static position on the content so that it can have a
     * higher stacking level than its previous sibling,
     * the #backgroundPreview element. */
    position: relative;
  }

  .ntp-background-logo {
    content: url(../images/module_icons/wallpaper_light.svg);
    height: 39px;
    margin: auto;
    margin-bottom: 16px;
    width: 44px;
  }

  @media (prefers-color-scheme: dark) {
    .ntp-background-logo {
      content: url(../images/module_icons/wallpaper_dark.svg);
    }
  }

  h1 {
    color: var(--cr-primary-text-color);
    font-size: 1.5rem;
    font-weight: 500;
    margin: 0;
    margin-bottom: 46px;
    outline: none;
    transition: color 400ms;
  }

  #backgroundPreview.active + .content h1 {
    color: white;
  }

  .ntp-backgrounds-grid {
    display: grid;
    grid-gap: 32px;
    grid-template-columns: repeat(3, 176px);
    grid-template-rows: repeat(2, 176px);
    width: 592px;
  }

  .option {
    align-items: stretch;
    border-radius: 4px;
    display: flex;
    height: 100%;
    overflow: hidden;
    padding: 0;
    text-align: start;
    transition: border-color 400ms, box-shadow 500ms;
    width: 100%;
  }

  #backgroundPreview.active + .content .option {
    border-color: var(--google-grey-refresh-700);
  }

  /* Remove outline when button is focused using the mouse. */
  .option:focus:not(.keyboard-focused) {
    outline: none;
  }

  .ntp-background-thumbnail {
    background-color: var(--cr-card-background-color);
    background-position: center center;
    background-repeat: no-repeat;
    background-size: cover;
    flex: 1;
  }

  .option-name {
    border-top: var(--cr-separator-line);
    color: var(--navi-wallpaper-text-color);
    height: 3rem;
    line-height: 3rem;
    overflow: hidden;
    padding: 0 .75rem;
    text-overflow: ellipsis;
  }

  .option[active] .option-name {
    background: var(--cr-checked-color);
    color: var(--cr-card-background-color);
  }

  .button-bar {
    margin-top: 56px;
  }

  #skipButton {
    background-color: var(--cr-card-background-color)
  }

  #skipButton:hover {
    background-image:
        linear-gradient(var(--hover-bg-color), var(--hover-bg-color));
  }

  /* Wallpaper Thumbnails */
  .art {
    background-image: url(../images/ntp_thumbnails/art.jpg);
  }

  .cityscape {
    background-image: url(../images/ntp_thumbnails/cityscape.jpg);
  }

  .earth {
    background-image: url(../images/ntp_thumbnails/earth.jpg);
  }

  .geometric-shapes {
    background-image: url(../images/ntp_thumbnails/geometric_shapes.jpg);
  }

  .landscape {
    background-image: url(../images/ntp_thumbnails/landscape.jpg);
  }
</style>
<div
    id="backgroundPreview"
    on-transitionend="onBackgroundPreviewTransitionEnd_">
</div>

<div class="content">
  <div class="ntp-background-logo"></div>
  <h1 tabindex="-1">$i18n{ntpBackgroundDescription}</h1>

  <div class="ntp-backgrounds-grid slide-in">
    <template is="dom-repeat" items="[[backgrounds_]]">
      <button
          active$="[[isSelectedBackground_(item, selectedBackground_)]]"
          class="option"
          on-click="onBackgroundClick_"
          on-keyup="onBackgroundKeyUp_"
          on-pointerdown="onBackgroundPointerDown_">
        <div
            class$="ntp-background-thumbnail [[item.thumbnailClass]]">
        </div>
        <div class="option-name">[[item.title]]</div>
      </button>
    </template>
  </div>

  <div class="button-bar">
    <cr-button id="skipButton" on-click="onSkipClicked_">
      $i18n{skip}
    </cr-button>
    <step-indicator model="[[indicatorModel]]"></step-indicator>
    <cr-button class="action-button" on-click="onNextClicked_">
      $i18n{next}
      <iron-icon icon="cr:chevron-right"></iron-icon>
    </cr-button>
  </div>
</div>