/* Global and Resets Styles*/
      * {
        box-sizing: border-box;
      }
      body {
        font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
        margin: 0;
        padding: 0;
        background: linear-gradient(135deg, #f8f9fa 0%, #e9ecef 100%);
        color: #333;
        min-height: 100vh;
      }
      .container {
        max-width: 1200px;
        margin: 0 auto;
        padding: 20px;
        position: relative;
        min-height: 80vh;
      }



/* Layout & Structure */
      .section {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        opacity: 0;
        visibility: hidden;
        transition: opacity 0.5s ease, visibility 0.5s ease;
        transform: translateY(20px);
      }
      .section.active {
        opacity: 1;
        visibility: visible;
        transform: translateY(0);
      }
      .section.hidden {
        display: none !important;
        opacity: 0 !important;
        visibility: hidden !important;
      }
      h5.author{
        display: block;
        text-align: center;
        margin-bottom: 20px;
        font-size: 12px;
      }



/* Homepage Styles */
      .homepage {
        background: linear-gradient(135deg, #6a11cb 0%, #2575fc 100%);
        color: white;
        border-radius: 20px;
        padding: 40px;
        text-align: center;
        box-shadow: 0 15px 30px rgba(0, 0, 0, 0.15);
        margin: 40px auto;
        max-width: 600px;
      }
      .homepage h1 {
        font-size: 3rem;
        margin-bottom: 10px;
        text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.2);
      }
      .homepage h4 {
        font-size: 1.2rem;
        font-weight: 300;
        margin-bottom: 30px;
      }
      .homepage.hidden {
        display: none !important;
      }
 



/* Button Styles */
      .btn-container {
        display: flex;
        flex-direction: column;
        gap: 15px;
        margin-top: 30px;
      }
      .btn {
        padding: 15px 25px;
        font-size: 1.1rem;
        border: none;
        border-radius: 50px;
        cursor: pointer;
        background: rgba(255, 255, 255, 0.2);
        color: white;
        backdrop-filter: blur(10px);
        box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
        transition: all 0.3s ease;
        display: flex;
        align-items: center;
        justify-content: center;
        gap: 10px;
      }
      .btn:hover {
        transform: translateY(-3px);
        box-shadow: 0 8px 20px rgba(0, 0, 0, 0.2);
        background: rgba(255, 255, 255, 0.3);
      }
      .btn:active {
        transform: translateY(1px);
      }
      .action-btn {
        padding: 12px 25px;
        border: none;
        border-radius: 10px;
        cursor: pointer;
        font-weight: 600;
        background: #2c3e50;
        color: white;
        display: flex;
        align-items: center;
        gap: 8px;
      }
      .action-btn:hover {
        opacity: 0.9;
        transform: translateY(-2px);
      }
      .back-btn {
        position: absolute;
        top: 20px;
        left: 20px;
        background: #2c3e50;
        color: white;
        border: none;
        border-radius: 50%;
        width: 40px;
        height: 40px;
        display: flex;
        align-items: center;
        justify-content: center;
        cursor: pointer;
        box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
      }
      .back-btn:hover {
        transform: translateY(-2px);
        box-shadow: 0 6px 15px rgba(0, 0, 0, 0.15);
      }
      .op-btn {
        padding: 12px 25px;
        border: 2px solid #3498db;
        background: white;
        color: #3498db;
        border-radius: 10px;
        cursor: pointer;
        font-weight: 600;
        transition: all 0.3s ease;
      }
      .op-btn.active {
        background: #3498db;
        color: white;
      }
      .op-btn:hover:not(.active) {
        background: #f8f9fa;
      }



/* Section & Content Styles */
      #learn, #quiz {
        background: white;
        border-radius: 20px;
        padding: 30px;
        box-shadow: 0 10px 25px rgba(0, 0, 0, 0.08);
        margin: 20px auto;
        max-width: 800px;
        position: relative;
      }
      #learn h1, #quiz h1 {
        color: #2c3e50;
        text-align: center;
        margin-bottom: 25px;
        font-size: 2.2rem;
      }



/* Form & Input Styles */
      .input-group {
        margin-bottom: 20px;
        text-align: left;
      }
      .input-group label {
        display: block;
        margin-bottom: 8px;
        font-weight: 600;
        color: #2c3e50;
      }
      .input-field {
        width: 100%;
        padding: 15px;
        border: 2px solid #e2e8f0;
        border-radius: 10px;
        font-size: 1.1rem;
        transition: all 0.3s ease;
      }
      .input-field:focus {
        outline: none;
        border-color: #3498db;
        box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.2);
      }



/* Operation Selector */
      .operation-selector {
        display: flex;
        justify-content: center;
        gap: 15px;
        margin: 25px 0;
        flex-wrap: wrap;
      }
     .action-buttons {
        display: flex;
        justify-content: center;
        flex-wrap: wrap;
        gap: 15px;
        margin: 25px 0;
      }



/* Output & Steps Styles */
      #output {
        background: #f8f9fa;
        border-radius: 10px;
        padding: 20px;
        margin-top: 20px;
        text-align: left;
        border-left: 4px solid #3498db;
        opacity: 0;
        transform: translateY(10px);
        transition: opacity 0.5s ease, transform 0.5s ease;
      }
      #output.show {
        opacity: 1;
        transform: translateY(0);
      }
      .step {
        margin-bottom: 15px;
        padding-bottom: 15px;
        border-bottom: 1px dashed #ddd;
      }
      .step:last-child {
        border-bottom: none;
      }
      .step-number {
        display: inline-block;
        background: #3498db;
        color: white;
        width: 25px;
        height: 25px;
        border-radius: 50%;
        text-align: center;
        margin-right: 10px;
        font-weight: bold;
      }
      .step-content {
        display: inline-block;
      }
      .final-result {
        background: #d4edda;
        padding: 15px;
        border-radius: 8px;
        margin-top: 20px;
        border-left: 4px solid #28a745;
      }
      .error {
        color: #dc3545;
        background-color: #f8d7da;
        border: 1px solid #f5c6cb;
        padding: 10px;
        border-radius: 5px;
        margin: 10px 0;
      }




/* Quiz System Style */
      .quiz-container {
        text-align: left;
      }
      .score-display {
        text-align: center;
        font-size: 1.2rem;
        margin-bottom: 20px;
        font-weight: 600;
        color: #2c3e50;
      }
      .quiz-question {
        background: #f8f9fa;
        padding: 20px;
        border-radius: 10px;
        margin-bottom: 15px;
      }
      .quiz-question h3 {
        margin-top: 0;
        color: #2c3e50;
      }
      .choice {
        padding: 12px 15px;
        background: white;
        border: 2px solid #e2e8f0;
        border-radius: 8px;
        margin: 8px 0;
        cursor: pointer;
        transition: all 0.2s ease;
      }
      .choice:hover {
        border-color: #3498db;
        background: #f0f7ff;
      }
      .choice.correct {
        background: #d4edda;
        border-color: #c3e6cb;
        color: #155724;
      }
      .choice.incorrect {
        background: #f8d7da;
        border-color: #f5c6cb;
        color: #721c24;
      }
      .choice.disabled {
        pointer-events: none;
      }
      .progress-bar {
        height: 8px;
        background: #e2e8f0;
        border-radius: 4px;
        margin: 20px 0;
        overflow: hidden;
      }
      .progress-bar-inner {
        height: 100%;
        background: linear-gradient(90deg, #6a11cb 0%, #2575fc 100%);
        width: 0%;
        transition: width 0.5s ease;
      }
      .quiz-footer {
        text-align: center;
        margin-top: 25px;
      }
      .quiz-results {
        text-align: center;
        padding: 30px;
      }
      .quiz-results h2 {
        color: #2c3e50;
        margin-bottom: 15px;
      }
      .quiz-result-buttons {
        display: flex;
        justify-content: space-between;
        margin-top: 20px;
      }
      .try-again-btn {
        padding: 12px;
        margin: 10px;
        order: 1;
      }
      .home-btn {
        order: 2;
        padding: 12px;
        margin: 10px;
      }



/* Animation & Transitions */
      @keyframes fadeIn {
        from {
          opacity: 0;
          transform: translateY(10px);
        }
        to {
          opacity: 1;
          transform: translateY(0);
        }
      }
      .quiz-question {
        animation: fadeIn 0.5s ease forwards;
      }
      .quiz-question:nth-child(1) { animation-delay: 0.1s; }
      .quiz-question:nth-child(2) { animation-delay: 0.2s; }
      .quiz-question:nth-child(3) { animation-delay: 0.3s; }

      

/* Responsive Design */
      /* Tablets */
      @media (max-width: 1024px) {
        .homepage {
          margin: 20px auto;
          padding: 30px;
        }

        #learn, #quiz {
          margin: 15px auto;
          padding: 20px;
          width: 90%; /* prevent stretching to edge */
        }

        .operation-selector,
        .action-buttons {
          flex-wrap: wrap;
          justify-content: center;
        }
      }
      /* Mobile */
      @media (max-width: 768px) {
        .homepage {
          margin: 10px auto;
          padding: 15px;
          width: 95%; /* shrink to viewport */
        }

        #learn, #quiz {
          margin: 10px auto;
          padding: 15px;
          width: 100%; /* take full width of container */
          box-sizing: border-box;
        }

        .operation-selector,
        .action-buttons {
          flex-direction: column;
          gap: 10px; /* spacing between items */
        }
      }