* { box-sizing: border-box; }
    body {
      margin: 0;
      min-height: 100vh;
      display: grid;
      place-items: center;
      padding: 24px;
      background: linear-gradient(135deg, #101c35, #243e66);
      font-family: Arial, Helvetica, sans-serif;
      color: #18243a;
    }
    .card {
      width: 100%;
      max-width: 400px;
      padding: 36px;
      background: #fff;
      border-radius: 18px;
      box-shadow: 0 20px 65px rgba(0, 0, 0, .25);
    }
    h1 { margin: 0 0 8px; font-size: 27px; }
    .subtitle { margin: 0 0 30px; color: #69768b; font-size: 14px; }
    label { display: block; margin: 18px 0 8px; font-size: 13px; font-weight: 600; }
    input {
      width: 100%;
      padding: 13px 14px;
      border: 1px solid #d6deea;
      border-radius: 9px;
      font: inherit;
      outline: none;
    }
    input:focus { border-color: #3977d5; box-shadow: 0 0 0 3px #3977d520; }
    button {
      width: 100%;
      margin-top: 26px;
      padding: 14px;
      border: 0;
      border-radius: 9px;
      background: #2764bd;
      color: #fff;
      font-size: 15px;
      font-weight: 600;
      cursor: pointer;
    }
    button:hover { background: #1e529f; }
    .error { display: none; margin-top: 18px; color: #b42318; font-size: 13px; }
    .error.visible { display: block; }