home-assistant.io/sass/custom/_tabbed_block.scss

.tabbed-content-block {
    background-color: #FAFAFA;
    margin: 16px 0;
    overflow: hidden;
    border-radius: 10px;
    box-shadow: -1px 0px 0px 0px #dfdfdf, 0px 0px 0px 1px #dfdfdf;
    box-sizing: border-box;
  
  .tabbed-content-block-tabs {
    overflow: hidden;
    padding: 0 8px;

    label {
        input{
            display:none;
          }
        input:checked + div{
            opacity: 1;
            border-bottom: 2px solid $primary-color;
          }

        div{
            float:left;
            padding: 8px;
            cursor: pointer;
            opacity: 0.7;
            transition: 0.3s;
            border-bottom: 2px solid transparent;
            font-size: 0.8em;
        }

        div:hover {
            opacity: 1;
        }
    }
  }

  .tabbed-content-block-content {
    padding: 8px 16px 0;
    display: none;
    animation: fadeEffect .5s;
  }

  @keyframes fadeEffect{
    0%{opacity:0}
    100%{opacity:1}
  }
}