:root {
            --primary-color: #3498db;
            --secondary-color: #2980b9;
            --success-color: #27ae60;
            --warning-color: #f39c12;
            --danger-color: #e74c3c;
            --dark-color: #2c3e50;
            --light-color: #ecf0f1;
            --gradient-bg: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            --card-shadow: 0 15px 35px rgba(0, 0, 0, 0.1);
            --hover-shadow: 0 10px 25px rgba(0, 0, 0, 0.2);
        }

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        
        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            background: var(--gradient-bg);
            min-height: 100vh;
            color: #333;
            line-height: 1.6;
        }
        
        .container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 20px;
        }
        
        .header {
            background: rgba(255, 255, 255, 0.95);
            padding: 30px;
            border-radius: 20px;
            box-shadow: var(--card-shadow);
            text-align: center;
            margin-bottom: 30px;
            backdrop-filter: blur(10px);
            animation: slideDown 0.8s ease-out;
        }
        
        @keyframes slideDown {
            from {
                opacity: 0;
                transform: translateY(-30px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }
        
        .header h1 {
            color: var(--dark-color);
            font-size: 2.5rem;
            margin-bottom: 10px;
            font-weight: 700;
            background: linear-gradient(45deg, var(--primary-color), var(--secondary-color));
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            background-clip: text;
        }
        
        .header p {
            color: #7f8c8d;
            font-size: 1.1rem;
            margin-bottom: 20px;
        }
        
        .stats {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 20px;
            margin-top: 20px;
        }
        
        .stat-card {
            background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
            color: white;
            padding: 20px;
            border-radius: 15px;
            text-align: center;
            transition: transform 0.3s ease, box-shadow 0.3s ease;
            animation: fadeInUp 0.6s ease-out;
            animation-fill-mode: both;
            cursor: pointer;
        }
        
        .stat-card:nth-child(2) { animation-delay: 0.1s; }
        .stat-card:nth-child(3) { animation-delay: 0.2s; }
        .stat-card:nth-child(4) { animation-delay: 0.3s; }
        
        @keyframes fadeInUp {
            from {
                opacity: 0;
                transform: translateY(30px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }
        
        .stat-card:hover {
            transform: translateY(-5px) scale(1.05);
            box-shadow: var(--hover-shadow);
        }
        
        .stat-number {
            font-size: 2rem;
            font-weight: bold;
            display: block;
        }
        
        .controls {
            background: rgba(255, 255, 255, 0.95);
            padding: 30px;
            border-radius: 20px;
            box-shadow: var(--card-shadow);
            margin-bottom: 30px;
            backdrop-filter: blur(10px);
            animation: slideUp 0.8s ease-out;
        }
        
        @keyframes slideUp {
            from {
                opacity: 0;
                transform: translateY(30px);
            }
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }
        
        .control-group {
            margin-bottom: 25px;
        }
        
        .control-group label {
            display: block;
            margin-bottom: 8px;
            font-weight: 600;
            color: var(--dark-color);
            font-size: 16px;
        }
        
        .control-group select, .control-group input {
            width: 100%;
            padding: 12px 15px;
            border: 2px solid #e0e6ed;
            border-radius: 10px;
            font-size: 16px;
            transition: all 0.3s ease;
            background: white;
            cursor: pointer;
        }
        
        .control-group select:focus, .control-group input:focus {
            outline: none;
            border-color: var(--primary-color);
            box-shadow: 0 0 0 3px rgba(52, 152, 219, 0.1);
            transform: translateY(-2px);
        }
        
        .control-group select:hover, .control-group input:hover {
            border-color: var(--secondary-color);
        }
        
        .filter-controls {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
            gap: 15px;
            margin-bottom: 20px;
        }

        #filtersContainer {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
            gap: 15px;
            margin-bottom: 20px;

            /* Animation defaults */
            max-height: 1000px;   /* enough to hold all filters */
            opacity: 1;
            overflow: hidden;
            transition: max-height 0.5s ease, opacity 0.5s ease;
            }

        #filtersContainer.hidden {
            max-height: 0;
            opacity: 0;
            pointer-events: none; /* avoid clicking hidden filters */
            }

        
        .hidden {
            display: none !important;
        }

        .button-group {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
            gap: 15px;
            margin-top: 25px;
        }
        
        .btn {
            padding: 15px 25px;
            border: none;
            border-radius: 12px;
            font-size: 16px;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s ease;
            text-transform: uppercase;
            letter-spacing: 1px;
            position: relative;
            overflow: hidden;
            text-decoration: none;
            display: inline-flex;
            align-items: center;
            justify-content: center;
        }
        
        .btn:disabled {
            opacity: 0.6;
            cursor: not-allowed;
            transform: none !important;
        }
        
        .btn::before {
            content: '';
            position: absolute;
            top: 0;
            left: -100%;
            width: 100%;
            height: 100%;
            background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
            transition: left 0.5s;
        }
        
        .btn:hover::before {
            left: 100%;
        }
        
        .btn-primary {
            background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
            color: white;
        }

        .quiz-controls {

            display: contents;
        }
        #loadBtn,#answersBtn,#pdfBtn,#quizBtn {
            margin-bottom: 10px;
        }

        
        .btn-success {
            background: linear-gradient(135deg, var(--success-color), #229954);
            color: white;
        }
        
        .btn-info {
            background: linear-gradient(135deg, #17a2b8, #138496);
            color: white;
        }
        
        .btn-warning {
            background: linear-gradient(135deg, var(--warning-color), #e67e22);
            color: white;
        }
        
        .btn:hover:not(:disabled) {
            transform: translateY(-2px);
            box-shadow: var(--hover-shadow);
        }
        
        .btn:active:not(:disabled) {
            transform: translateY(0);
        }
        
        .content {
            background: rgba(255, 255, 255, 0.95);
            padding: 30px;
            border-radius: 20px;
            box-shadow: var(--card-shadow);
            backdrop-filter: blur(10px);
            animation: fadeIn 1s ease-out;
        }
        
        @keyframes fadeIn {
            from { opacity: 0; }
            to { opacity: 1; }
        }
        
        .question-container {
            margin-bottom: 30px;
            padding: 25px;
            border: 2px solid #e0e6ed;
            border-radius: 15px;
            background: #f8f9fa;
            transition: all 0.3s ease;
            animation: questionSlide 0.5s ease-out;
            animation-fill-mode: both;
        }
        
        @keyframes questionSlide {
            from {
                opacity: 0;
                transform: translateX(-20px);
            }
            to {
                opacity: 1;
                transform: translateX(0);
            }
        }
        
        .question-container:hover {
            border-color: var(--primary-color);
            box-shadow: 0 5px 15px rgba(52, 152, 219, 0.1);
            transform: translateY(-2px);
        }
        
        .question-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 15px;
            flex-wrap: wrap;
            gap: 10px;
        }
        
        .question-number {
            background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
            color: white;
            width: 35px;
            height: 35px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-weight: bold;
        }
        
        .question-meta {
            display: flex;
            gap: 10px;
            align-items: center;
            flex-wrap: wrap;
        }
        
        .question-year {
            background: var(--warning-color);
            color: white;
            padding: 5px 12px;
            border-radius: 15px;
            font-size: 12px;
            font-weight: 600;
        }
        
        .difficulty-indicator {
            display: inline-block;
            padding: 5px 12px;
            border-radius: 15px;
            font-size: 12px;
            font-weight: 600;
            text-transform: uppercase;
        }

        .difficulty-easy { background: #d4edda; color: #155724; }
        .difficulty-medium { background: #fff3cd; color: #856404; }
        .difficulty-hard { background: #f8d7da; color: #721c24; }
        
        .question {
            font-size: 1.1rem;
            font-weight: 600;
            margin-bottom: 15px;
            line-height: 1.5;
            color: var(--dark-color);
        }
        
        .options {
            margin-bottom: 15px;
        }
        
        .option {
            padding: 12px 15px;
            margin: 8px 0;
            border: 1px solid #ddd;
            border-radius: 8px;
            cursor: pointer;
            transition: all 0.3s ease;
            background: white;
            position: relative;
            user-select: none;
        }
        
        .option::before {
            content: '';
            position: absolute;
            left: 0;
            top: 0;
            height: 100%;
            width: 0;
            background: linear-gradient(90deg, var(--primary-color), transparent);
            transition: width 0.3s ease;
            border-radius: 8px 0 0 8px;
        }
        
        .option:hover::before {
            width: 4px;
        }
        
        .option:hover {
            background: #e3f2fd;
            border-color: var(--primary-color);
            transform: translateX(5px);
        }
        
        .option.correct {
            background: #d4edda !important;
            border-color: var(--success-color) !important;
            color: #155724 !important;
            font-weight: 600;
            animation: correctAnswer 0.5s ease-out;
        }
        
        @keyframes correctAnswer {
            0% { transform: scale(1); }
            50% { transform: scale(1.05); }
            100% { transform: scale(1); }
        }
        
        .option.incorrect {
            background: #f8d7da !important;
            border-color: var(--danger-color) !important;
            color: #721c24 !important;
            font-weight: 600;
        }
        
        .option.selected {
            background: #e3f2fd;
            border-color: var(--primary-color);
            font-weight: 600;
            transform: translateX(5px);
        }
        
        .explanation {
            background: #fff3cd;
            border-left: 4px solid #ffc107;
            padding: 15px;
            border-radius: 8px;
            margin-top: 15px;
            font-style: italic;
            animation: slideDown 0.5s ease-out;
        }
        
        .progress-container {
            margin: 20px 0;
            margin-top: -30px;
        }
        
        .progress-label {
            display: flex;
            justify-content: space-between;
            margin-bottom: 8px;
            font-weight: 600;
            color: var(--dark-color);
        }
        
        .progress-bar {
            width: 100%;
            height: 10px;
            background: var(--light-color);
            border-radius: 5px;
            overflow: hidden;
            box-shadow: inset 0 2px 4px rgba(0,0,0,0.1);
        }
        
        .progress-fill {
            height: 100%;
            background: linear-gradient(90deg, var(--success-color), #2ecc71);
            width: 0%;
            transition: width 0.5s ease;
            border-radius: 5px;
        }
        
        .loading {
            text-align: center;
            padding: 50px;
            color: #7f8c8d;
            font-size: 1.2rem;
            position: relative;
        }
        
        .loading::after {
            content: '';
            display: inline-block;
            width: 20px;
            height: 20px;
            border: 2px solid var(--primary-color);
            border-radius: 50%;
            border-top-color: transparent;
            animation: spin 1s linear infinite;
            margin-left: 10px;
        }
        
        @keyframes spin {
            to { transform: rotate(360deg); }
        }
        
        .quiz-header {
            text-align: center;
            margin-bottom: 20px;
            padding: 20px;
            background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
            color: white;
            border-radius: 15px;
            animation: pulseGlow 2s infinite;
        }
        
        @keyframes pulseGlow {
            0%, 100% { box-shadow: 0 0 20px rgba(52, 152, 219, 0.3); }
            50% { box-shadow: 0 0 30px rgba(52, 152, 219, 0.6); }
        }
        
        .quiz-complete {
            text-align: center;
            padding: 50px;
            background: linear-gradient(135deg, #f8f9fa, #e9ecef);
            border-radius: 20px;
            animation: celebration 0.8s ease-out;
        }
        
        @keyframes celebration {
            0% { transform: scale(0.8); opacity: 0; }
            100% { transform: scale(1); opacity: 1; }
        }
        
        .score-display {
            font-size: 3rem;
            font-weight: bold;
            margin: 20px 0;
            background: linear-gradient(45deg, var(--success-color), #2ecc71);
            -webkit-background-clip: text;
            -webkit-text-fill-color: transparent;
            background-clip: text;
        }
        
        @media (max-width: 768px) {
            .header h1 {
                font-size: 2rem;
            }
            
            .container {
                padding: 10px;
            }
            
            .button-group {
                grid-template-columns: 1fr;
            }
            
            .stats {
                grid-template-columns: 1fr 1fr;
            }
            
            .filter-controls {
                grid-template-columns: 1fr;
            }
        }
        
        .print-section {
            /* display: none; */
        }
        
        @media print {
            body * {
                visibility: hidden;
            }
            
            .print-section, .print-section * {
                visibility: visible;
            }
            
            .print-section {
                position: absolute;
                left: 0;
                top: 0;
                width: 100%;
            }
            
            .question-container {
                break-inside: avoid;
                margin-bottom: 20px;
                border: 1px solid #000;
            }
        }

        html {
            scroll-behavior: smooth;
        }

        ::-webkit-scrollbar {
            width: 8px;
        }

        ::-webkit-scrollbar-track {
            background: #f1f1f1;
        }

        ::-webkit-scrollbar-thumb {
            background: var(--primary-color);
            border-radius: 4px;
        }

        ::-webkit-scrollbar-thumb:hover {
            background: var(--secondary-color);
        }

        .notification {
            position: fixed;
            top: 20px;
            right: 20px;
            padding: 15px 20px;
            border-radius: 8px;
            color: white;
            font-weight: 600;
            z-index: 10000;
            animation: slideInRight 0.3s ease-out;
            max-width: 300px;
            word-wrap: break-word;
            box-shadow: var(--card-shadow);
        }

        @keyframes slideInRight {
            from {
                transform: translateX(100%);
                opacity: 0;
            }
            to {
                transform: translateX(0);
                opacity: 1;
            }
        }

/* Import control styling */
.import-group { margin: 12px 0; padding: 10px; border: 1px dashed rgba(0,0,0,.2); border-radius: 10px; }
.import-row { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.import-row input[type="file"] { max-width: 280px; }
.import-group .hint { display:block; opacity: .8; }


/* ===== Import UI Polished Card ===== */
.import-group {
  background: #ffffff;
  box-shadow: 0 6px 18px rgba(0,0,0,0.08);
  border-radius: 16px;
  padding: 18px 20px;
  margin: 22px auto;
  max-width: 900px;
  border: 1px solid rgba(0,0,0,0.06);
}
.import-group label {
  font-weight: 700;
  font-size: 1.05rem;
  color: #34495e;
  margin-bottom: 10px;
  display: block;
}
.import-row {
  display: flex;
  gap: 12px;
  align-items: center;
  flex-wrap: wrap;
}
#importFile {
  flex: 1;
  min-width: 260px;
  padding: 10px 12px;
  border: 1px solid #d0d7de;
  border-radius: 10px;
  background: #fafbfc;
}
#importBtn {
  background: #4f46e5;
  color: #fff;
  font-weight: 600;
  border: none;
  border-radius: 10px;
  padding: 10px 14px;
  cursor: pointer;
  transition: transform 0.05s ease, box-shadow 0.2s ease, background 0.2s ease;
  box-shadow: 0 6px 14px rgba(79,70,229,0.25);
}
#importBtn:hover { background: #4338ca; }
#importBtn:active { transform: translateY(1px); }
.import-group .hint { display:block; opacity:.75; margin-top:8px; font-size:.92rem; }

#quizTimerDisplay {
  font-weight: bold;
  font-size: 1.2rem;
}

/* Final 10s blinking */
.final-blink {
  animation: blinkWarning 1.5s infinite;
}

@keyframes blinkWarning {
  0%   { color: #e74c3c; }   /* red */
  50%  { color: #e79614aa; }  /* orange */
  100% { color: #e74c3c; }   /* red */
}