.tip-calculator {
      background: #ffffff;
      border-radius: 16px;
      box-shadow: 0 10px 25px rgba(0,0,0,0.1);
      max-width: 400px;
      width: 100%;
      margin: auto;
      margin-bottom: 30px;
    }

    h1 {
      text-align: center;
      color: #333;
      margin-bottom: 20px;
    }

    .input-group {
      margin-bottom: 20px;
    }

    label {
      display: block;
      color: #555;
      margin-bottom: 6px;
      font-weight: 500;
    }

    input[type="number"] {
      width: 100%;
      padding: 10px;
      border: 2px solid #ddd;
      border-radius: 8px;
      font-size: 16px;
    }

    .tip-options {
      display: flex;
      flex-wrap: wrap;
      gap: 8px;
    }

    .tip-btn {
      flex: 1 1 30%;
      padding: 10px;
      background: #e0e0e0;
      border: none;
      border-radius: 8px;
      font-weight: bold;
      cursor: pointer;
      transition: background 0.3s;
    }

    .tip-btn:hover {
      background: #4caf50;
      color: white;
    }

    .tip-btn.active {
      background: #4caf50;
      color: white;
      box-shadow: 0 0 0 2px rgba(76, 175, 80, 0.3);
    }

    #custom-tip {
      flex: 1 1 100%;
      margin-top: 10px;
    }

    .results {
      background: #f9f9f9;
      padding: 15px;
      border-radius: 10px;
      margin-top: 20px;
    }

    .results div {
      display: flex;
      justify-content: space-between;
      margin-bottom: 10px;
    }

    strong {
      color: #2e7d32;
    }

    .reset-btn {
      margin-top: 20px;
      width: 100%;
      padding: 12px;
      background: #ff5252;
      border: none;
      border-radius: 8px;
      color: white;
      font-weight: bold;
      cursor: pointer;
      transition: background 0.3s;
    }

    .reset-btn:hover {
      background: #d32f2f;
    }