* {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    body {
      font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
      background-color: #2c3e50;
      padding: 20px;
      min-height: 100vh;
    }

    .container {
      max-width: 1400px;
      margin: 0 auto;
      background: white;
      padding: 30px;
      border-radius: 12px;
      box-shadow: 0 6px 20px rgba(0,0,0,0.15);
    }

    /* Navbar */
    .navbar {
      display: flex;
      justify-content: space-between;
      align-items: center;
      margin-bottom: 25px;
      flex-wrap: wrap;
      gap: 15px;
    }

    .navbar h1 {
      font-size: 2rem;
      color: #2c3e50;
    }

    .nav-buttons {
      display: flex;
      gap: 10px;
    }

    .nav-btn {
      background-color: #2c3e50;
      color: white;
      padding: 8px 16px;
      border: none;
      border-radius: 8px;
      cursor: pointer;
      font-weight: 600;
      transition: background-color 0.3s ease;
    }

    .nav-btn:hover {
      background-color: #2980b9;
    }

    /* Initial Screen */
    .initial-screen {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      min-height: 60vh;
      gap: 30px;
    }

    .initial-screen h1 {
      font-size: 2.5rem;
      color: #2c3e50;
      margin-bottom: 15px;
      text-align: center;
    }

    .initial-screen p {
      color: #555;
      font-size: 18px;
      margin-bottom: 30px;
      text-align: center;
    }

    .mode-buttons {
      display: flex;
      flex-direction: column;
      gap: 20px;
      width: 100%;
      max-width: 500px;
    }

    .mode-btn {
      width: 100%;
      padding: 18px 30px;
      font-size: 18px;
      font-weight: 600;
      border: none;
      border-radius: 8px;
      cursor: pointer;
      background-color: #2c3e50;
      color: white;
      transition: all 0.3s ease;
    }

    .mode-btn:hover {
      background-color: #2980b9;
      transform: translateY(-2px);
    }

    /* Modal */
    .modal {
      display: none;
      position: fixed;
      z-index: 1000;
      left: 0;
      top: 0;
      width: 100%;
      height: 100%;
      overflow: auto;
      background-color: rgba(0,0,0,0.6);
    }

    .modal-content {
      background-color: #fff;
      margin: 5% auto;
      padding: 2px 20px 30px 20px;
      border-radius: 12px;
      max-width: 800px;
      box-shadow: 0 6px 20px rgba(0,0,0,0.25);
      font-size: 16px;
      line-height: 1.8;
    }

    .modal-header {
      display: flex;
      justify-content: space-between;
      align-items: center;
      margin-bottom: 20px;
      padding-bottom: 15px;
    }

    .modal-header h2 {
      color: #2c3e50;
      font-size: 1.8rem;
    }

    .close {
      font-size: 32px;
      font-weight: bold;
      cursor: pointer;
      color: #666;
      transition: color 0.3s ease;
    }

    .close:hover {
      color: #e53935;
    }

    .modal-body {
      color: #555;
    }

    .modal-body b {
      color: #2c3e50;
    }

    /* Visibility */
    .initial-screen,
    .single-area-container,
    .two-area-container {
      display: none;
    }
    
    .visible {
      display: block;
      animation: fadeIn 0.4s ease;
    }

    .initial-screen.visible {
      display: flex;
    }

    @keyframes fadeIn {
      from { opacity: 0; }
      to { opacity: 1; }
    }

    /* Section Styling */
    .section {
      margin-bottom: 30px;
      padding: 20px;
      background-color: #fafbfc;
      border-radius: 8px;
      border: 1px solid #ddd;
    }

    h2 {
      color: #34495e;
      margin-bottom: 20px;
      font-size: 1.5rem;
    }

    /* Layout */
    .row {
      display: flex;
      flex-wrap: wrap;
      gap: 25px;
    }

    .column {
      flex: 1;
      min-width: 340px;
    }

    /* Left Column - Inputs and Graph */
    .left-column {
      display: flex;
      flex-direction: column;
      gap: 25px;
    }

    .input-container {
      display: flex;
      flex-direction: column;
      gap: 8px;
    }

    .input-row {
      display: flex;
      align-items: center;
      gap: 15px;
      margin-bottom: 12px;
      flex-wrap: wrap;
    }

    .input-row label {
      min-width: 200px;
      font-weight: 500;
      color: #555;
      flex: 1;
    }

    .input-row input {
      padding: 8px 12px;
      border: 2px solid #dfe6e9;
      border-radius: 6px;
      width: 150px;
      transition: border-color 0.3s ease;
    }

    .input-row input:focus {
      outline: none;
      border-color: #3498db;
    }

    .button-container {
      text-align: center;
      margin-top: 20px;
    }

    .plot-btn {
      background-color: #2c3e50;
      color: white;
      padding: 12px 30px;
      border: none;
      border-radius: 6px;
      font-weight: 600;
      cursor: pointer;
      font-size: 16px;
      transition: background-color 0.3s ease;
    }

    .plot-btn:hover {
      background-color: #2980b9;
    }

    .image-container {
      text-align: center;
      margin-bottom: 25px;
      padding: 25px;
      background-color: #fafbfc;
      border-radius: 8px;
      border: 1px solid #ddd;
    }

    .imageW {
       width: 100%;
       max-width: 600px;  /* keep original width on large screens */
       height: 370px;      /* maintain aspect ratio */
       display: block;
        
    }
 
    .plots-container {
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 25px;
      background: white;
      border-radius: 8px;
      padding: 10px;
      box-shadow: 0 2px 8px rgba(0,0,0,0.1);
    }
    .plots-container2 {
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 25px;
      background: white;
      border-radius: 8px;
      padding: 83px;
      box-shadow: 0 2px 8px rgba(0,0,0,0.1);
    }
    /* Single graph below inputs */
    .left-graph {
      width: 100%;
      background: white;
      border-radius: 8px;
      padding: 15px;
      box-shadow: 0 2px 8px rgba(0,0,0,0.1);
    }
 
    canvas {
      width: 100% !important;
      max-width: 100%;
      height: 300px !important;
      display: block;
      margin: 0 auto;
    }
    footer {
      text-align: center;
      padding: 10px;
      margin-top: 30px;
      margin-left: -30px;
      margin-right: -30px;
      margin-bottom: -42px;
      background-color: #466581;
      color: white;
      border-radius: 0 0 12px 12px;
      font-size: 16px;
    }

    /* Responsive */
    @media (max-width: 768px) {
      .navbar {
        flex-direction: column;
        align-items: flex-start;
      }

      .navbar h1 {
        font-size: 1.5rem;
      }

      .input-row {
        flex-direction: column;
        align-items: flex-start;
      }

      .input-row label {
        width: 100%;
        min-width: auto;
      }

      .input-row input {
        width: 100%;
      }

      .mode-buttons {
        width: 100%;
      }
    }