html, body { margin: 0; padding: 0; background: #f6fcff; min-height: 100%; }
      body { font-family: "Segoe UI", Arial, sans-serif; min-height: 100vh; }
      .container {
        max-width: 620px;
        margin: 38px auto 0 auto;
        background: #fff;
        border-radius: 18px;
        box-shadow: 0 4px 22px #13d2b033;
        padding: 28px 18px 22px 18px;
      }
      .logo {
        font-size: 1.25em;
        color: #19788a;
        font-weight: bold;
        margin-bottom: 6px;
        text-align: center;
      }
      .desc {
        color: #357890;
        text-align: center;
        margin-bottom: 18px;
        font-size: 0.98em;
      }
      .input-area,
      .output-area {
        width: 100%;
        box-sizing: border-box;
        min-height: 120px;
        border: 1.2px solid #cce9ef;
        border-radius: 9px;
        padding: 11px;
        font-size: 1em;
        background: #fafdff;
        font-family: "Fira Mono", "Menlo", monospace;
        resize: vertical;
        margin-bottom: 8px;
        line-height: 1.6;
        overflow-x: auto;
      }
      .output-area { background: #e7f9f3; }
      .btn, .btn-copy {
        background: #1495c5;
        color: #fff;
        border: none;
        border-radius: 7px;
        padding: 10px 18px;
        margin: 10px 8px 0 0;
        cursor: pointer;
        font-size: 1.03em;
        transition: background 0.18s;
      }
      .btn:active, .btn-copy:active { background: #0b6180; }
      .info-msg {
        color: #1c9b56;
        font-size: 0.95em;
        margin: 6px 0 10px 0;
        text-align: center;
      }
      .footer {
        color: #789;
        text-align: center;
        font-size: 0.94em;
        margin-top: 22px;
      }
      @media (max-width: 700px) {
        .container { max-width: 98vw; padding: 12px 2vw 14px 2vw; }
        .input-area, .output-area { font-size: 0.98em; }
      }
      #backBtn {
        position: fixed;
        left: 50%;
        bottom: 32px;
        transform: translateX(-50%);
        background: #13b6a7;
        color: #fff;
        font-weight: 700;
        border: none;
        border-radius: 2rem;
        padding: 0.58em 1.5em;
        box-shadow: 0 4px 16px #13d2b066;
        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: #0e8078; transform: translateX(-50%) scale(1.04);}
      @media (max-width: 600px) {
        #backBtn { bottom: 18px; font-size: 0.98em; padding: 0.48em 1em; }
      }