body {
        background: #f7fcff;
        font-family: "Segoe UI", Arial, sans-serif;
        margin: 0;
        color: #223;
      }
      .container {
        max-width: 420px;
        margin: 30px auto 0 auto;
        background: #fff;
        border-radius: 18px;
        box-shadow: 0 4px 22px #117c9a28;
        padding: 22px 13px 18px 13px;
      }
      .logo {
        font-size: 1.25em;
        text-align: center;
        color: #117c9a;
        font-weight: bold;
        margin-bottom: 10px;
      }
      .desc {
        text-align: center;
        color: #127080;
        margin-bottom: 15px;
        font-size: 1.07em;
      }
      textarea {
        width: 100%;
        min-height: 110px;
        border: 1.2px solid #b9eaf8;
        border-radius: 8px;
        padding: 12px;
        font-size: 1.09em;
        background: #fafdff;
        margin-bottom: 11px;
        font-family: inherit;
      }
      .input-row {
        margin-bottom: 8px;
      }
      .slider-label {
        color: #19788a;
        font-size: 1.03em;
        margin-right: 8px;
      }
      #summaryLength {
        vertical-align: middle;
      }
      #lengthVal {
        margin-left: 6px;
        color: #127080;
      }
      .action-btn {
        width: 100%;
        background: #117c9a;
        color: #fff;
        border: none;
        border-radius: 8px;
        font-size: 1.17em;
        font-weight: bold;
        padding: 12px 0;
        margin: 11px 0 10px 0;
        cursor: pointer;
      }
      .action-btn:active {
        background: #09506d;
      }
      .output-box {
        min-height: 52px;
        background: #f7fcff;
        border: 1.1px solid #b2e0ee;
        border-radius: 8px;
        font-size: 1.07em;
        padding: 12px 10px 10px 12px;
        white-space: pre-wrap;
      }
      .footer {
        color: #789;
        text-align: center;
        font-size: 0.93em;
        margin-top: 14px;
      }
      #backBtn {
        position: fixed;
        left: 50%;
        bottom: 32px;
        transform: translateX(-50%);
        background: #117c9a;
        color: #fff;
        font-weight: 700;
        border: none;
        border-radius: 2rem;
        padding: 0.58em 1.5em;
        box-shadow: 0 4px 16px #117c9a22;
        font-size: 1.09em;
        text-decoration: none;
        cursor: pointer;
        letter-spacing: 0.01em;
        transition:
          background 0.15s,
          transform 0.12s;
        z-index: 2000;
      }
      #backBtn:hover {
        background: #09506d;
        transform: translateX(-50%) scale(1.04);
      }
      @media (max-width: 600px) {
        .container {
          max-width: 99vw;
          padding: 10px 2vw 13px 2vw;
        }
        #backBtn {
          bottom: 18px;
          font-size: 0.98em;
          padding: 0.48em 1em;
        }
      }