body {
      background: linear-gradient(135deg, #1a1a2e, #16213e);
      color: #fff;
      font-family: "Segoe UI", sans-serif;
      text-align: center;
      height: 100vh;
      margin: 0;
      display: flex;
      flex-direction: column;
      justify-content: center;
      align-items: center;
    }
    h1 {
      font-size: 3em;
      margin-bottom: 10px;
      color: #00d4ff;
    }
    p {
      font-size: 1.2em;
      margin-bottom: 20px;
    }
    .countdown {
      display: flex;
      gap: 20px;
      font-size: 2em;
      font-weight: bold;
    }
    .countdown div {
      background: rgba(255, 255, 255, 0.1);
      padding: 20px 25px;
      border-radius: 10px;
      box-shadow: 0 0 10px #00d4ff;
      min-width: 80px;
    }
    .label {
      display: block;
      font-size: 0.5em;
      font-weight: normal;
      color: #ccc;
    }
    footer {
      position: absolute;
      bottom: 20px;
      font-size: 0.9em;
      color: #aaa;
    }
    
    /* 📱 Responsive cho điện thoại */
    @media (max-width: 600px) {
      h1 {
        font-size: 1.8em;
      }
      p {
        font-size: 1em;
      }
      .countdown div {
        padding: 15px 10px;
        min-width: 60px;
      }
      .time-value {
        font-size: 1.4em;
      }
    }