body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
  }
  
  .converter-card {
    max-width: 420px;
    width: 100%;
    padding: 30px;
    border-radius: 16px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
    background: #ffffff;
    border: 1px solid #e1e8ed;
  }
  
  .converter-card h3 {
    margin-top: 0;
    text-align: center;
    color: #1e3c72;
    font-size: 1.5em;
    margin-bottom: 20px;
    letter-spacing: 0.5px;
  }
  
  .form-group {
    margin-bottom: 18px;
  }
  
  .form-group label {
    display: block;
    margin-bottom: 6px;
    font-weight: 600;
    font-size: 0.9em;
    color: #4a5568;
  }
  
  .form-group input, 
  .form-group select {
    width: 100%;
    padding: 12px;
    box-sizing: border-box;
    border: 1px solid #cbd5e0;
    border-radius: 8px;
    font-size: 1em;
    background-color: #f8fafc;
    transition: all 0.3s ease;
  }
  
  .form-group input:focus, 
  .form-group select:focus {
    border-color: #3182ce;
    background-color: #ffffff;
    outline: none;
    box-shadow: 0 0 0 3px rgba(49, 130, 206, 0.15);
  }
  
  .result-box {
    margin-top: 25px;
    padding: 15px;
    background: linear-gradient(135deg, #1e3c72 0%, #2a5298 100%);
    border-radius: 8px;
    text-align: center;
    font-weight: bold;
    font-size: 1.1em;
    color: #ffffff;
    box-shadow: 0 4px 10px rgba(30, 60, 114, 0.2);
  }