:root {
    --teal-green: #20c997;
    --navy-blue: #001f3f;
    --dark-navy: #001737;
    --light-gray: #ccc;
    --white: #ffffff;
    --muted-gray: #aaa;
  }
  
  body {
    font-family: 'Segoe UI', sans-serif;
    background: #f4f4f4;
    margin: 0;
    padding: 0;
    color: #333;
  }
  
  .container {
    max-width: 600px;
    margin: auto;
    padding: 20px;
  }
  
  .gradient-title {
    text-align: center;
    font-size: 2em;
    font-weight: bold;
    background: linear-gradient(to right, var(--teal-green), var(--navy-blue));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
  }
  
  form {
    background: var(--white);
    padding: 25px;
    border-radius: 10px;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.05);
  }
  
  .form-group {
    margin-bottom: 16px;
  }
  
  input[type="number"] {
    width: 100%;
    max-width: 100%;
    padding: 12px;
    font-size: 1em;
    border: 1px solid var(--light-gray);
    border-radius: 6px;
    box-sizing: border-box;
  }
  
  .button-row {
    display: flex;
    justify-content: space-between;
    gap: 10px;
  }
  
  .calculate-btn, .clear-btn {
    flex: 1;
    padding: 12px;
    font-size: 1em;
    border-radius: 6px;
    border: none;
  }
  
  .calculate-btn {
    background: var(--navy-blue);
    color: var(--white);
    font-weight: bold;
  }
  
  .clear-btn {
    background: var(--light-gray);
    color: #000;
  }
  
  .download-btn {
    margin-top: 20px;
    width: 100%;
    padding: 12px;
    background: var(--teal-green);
    border: none;
    border-radius: 6px;
    color: var(--white);
    font-weight: bold;
  }
  
  .results, .table-container {
    margin-top: 25px;
    background: var(--white);
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.05);
  }
  
  table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 15px;
  }
  
  th, td {
    padding: 10px;
    text-align: center;
    border-bottom: 1px solid #ddd;
    font-size: 0.95em;
  }
  
  .hidden {
    display: none;
  }
  
  .spinner {
    width: 30px;
    height: 30px;
    margin: 15px auto;
    border: 4px solid var(--teal-green);
    border-top: 4px solid transparent;
    border-radius: 50%;
    animation: spin 1s linear infinite;
  }
  
  @keyframes spin {
    to { transform: rotate(360deg); }
  }
  
  .footer {
    text-align: center;
    margin-top: 30px;
    font-size: 0.9em;
    color: var(--muted-gray);
  }