/* Enhanced CSS with Advanced Animations and Modern Design */

/* CSS Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* Advanced CSS Custom Properties with Neon Theme */
:root {
    /* Neon Theme Colors */
    --neon-teal: #00CEDA;
    --neon-pink: #FF1493;
    --neon-yellow: #FFD700;
    --dark-metallic: #1a1a1a;
    --neon-glow-teal: 0 0 20px rgba(0, 206, 218, 0.8);
    --neon-glow-pink: 0 0 20px rgba(255, 20, 147, 0.8);
    --neon-glow-yellow: 0 0 20px rgba(255, 215, 0, 0.8);

    /* Modern Gradient Colors */
    --primary-gradient: linear-gradient(135deg, var(--neon-teal) 0%, var(--neon-pink) 100%);
    --secondary-gradient: linear-gradient(135deg, var(--neon-pink) 0%, var(--neon-yellow) 100%);
    --success-gradient: linear-gradient(135deg, var(--neon-teal) 0%, #00b09b 100%);
    --warning-gradient: linear-gradient(135deg, var(--neon-yellow) 0%, #f7b733 100%);
    --info-gradient: linear-gradient(135deg, var(--neon-pink) 0%, var(--neon-teal) 100%);

    /* Glassmorphism Variables for Dark Metallic Theme */
    --glass-bg: rgba(26, 26, 26, 0.7);
    --glass-border: rgba(0, 206, 218, 0.3);
    --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.5);
    --glass-blur: blur(8px);

    /* Enhanced Shadows */
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.6);
    --shadow-xl: 0 16px 64px rgba(0, 0, 0, 0.8);
    --shadow-glow: var(--neon-glow-teal);

    /* Animation Durations */
    --transition-fast: 0.2s;
    --transition-normal: 0.3s;
    --transition-slow: 0.5s;
    --transition-bounce: 0.6s;

    /* Modern Colors */
    --primary-color: var(--neon-teal);
    --primary-dark: var(--neon-pink);
    --primary-light: var(--neon-yellow);
    --secondary-color: var(--neon-pink);
    --accent-color: var(--neon-teal);
    --background: #0a0a0a;
    --surface: var(--dark-metallic);
    --surface-light: #2a2a2a;
    --text-primary: #ffffff;
    --text-secondary: #e0e0e0;
    --text-muted: #a0a0a0;
    --border-color: rgba(0, 206, 218, 0.2);

    /* Particle Animation Colors */
    --particle-colors: var(--neon-teal), var(--neon-pink), var(--neon-yellow), #00b09b, #f7b733, #4facfe;
}

/* Enhanced Base Typography and Layout */
html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: 'Orbitron', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    font-weight: 400;
    line-height: 1.6;
    color: var(--text-primary);
    background: var(--background);
    background-image:
        radial-gradient(circle at 20% 50%, rgba(0, 206, 218, 0.15) 0%, transparent 50%),
        radial-gradient(circle at 80% 80%, rgba(255, 20, 147, 0.15) 0%, transparent 50%),
        radial-gradient(circle at 40% 20%, rgba(255, 215, 0, 0.1) 0%, transparent 50%);
    background-attachment: fixed;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    position: relative;
    overflow-x: hidden;
}

/* Scroll Progress Bar */
.scroll-progress-bar {
    position: fixed;
    top: 0;
    left: 0;
    height: 4px;
    background: var(--primary-gradient);
    width: 0%;
    z-index: 9999;
    transition: width 0.2s ease-out;
    box-shadow: var(--neon-glow-teal);
}

/* Floating Action Buttons */
.fab-container {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
    z-index: 999;
}

.fab {
    width: 56px;
    height: 56px;
    border-radius: 50%;
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-lg);
    transition: all var(--transition-normal) cubic-bezier(0.4, 0, 0.2, 1);
    backdrop-filter: var(--glass-blur);
    position: relative;
    overflow: hidden;
}

.fab::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--primary-gradient);
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.fab svg {
    position: relative;
    z-index: 1;
    transition: transform var(--transition-normal);
}

.fab-primary {
    background: var(--glass-bg);
    color: var(--neon-teal);
    border: 2px solid var(--neon-teal);
}

.fab-secondary {
    background: var(--glass-bg);
    color: var(--neon-pink);
    border: 2px solid var(--neon-pink);
    opacity: 0;
    transform: translateY(20px);
    pointer-events: none;
}

.fab-secondary.visible {
    opacity: 1;
    transform: translateY(0);
    pointer-events: all;
}

.fab:hover {
    transform: scale(1.1) rotate(10deg);
    box-shadow: var(--shadow-xl), var(--neon-glow-teal);
}

.fab:hover::before {
    opacity: 0.2;
}

.fab:hover svg {
    transform: scale(1.1);
}

.fab:active {
    transform: scale(0.95);
}

/* Animated Background Particles */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: -1;
    opacity: 0.4;
}

/* Enhanced Header with Gradient and Glassmorphism */
.site-header {
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border-bottom: 1px solid var(--glass-border);
    color: white;
    padding: 3rem 1rem;
    text-align: center;
    box-shadow: var(--shadow-lg);
    position: relative;
    overflow: hidden;
    animation: slideDown 0.8s ease-out;
}

/* Header Badge */
.header-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border: 1px solid var(--neon-teal);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    margin-bottom: 1rem;
    animation: bounceIn 0.8s ease-out;
    box-shadow: var(--neon-glow-teal);
}

.badge-pulse {
    width: 8px;
    height: 8px;
    background: var(--neon-teal);
    border-radius: 50%;
    animation: pulse 2s ease-in-out infinite;
    box-shadow: 0 0 10px var(--neon-teal);
}

.badge-text {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--neon-teal);
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

/* Stats Bar */
.stats-bar {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 2rem;
    margin-top: 2rem;
    padding: 1.5rem;
    background: rgba(255, 255, 255, 0.05);
    backdrop-filter: var(--glass-blur);
    border-radius: 20px;
    border: 1px solid var(--glass-border);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
    animation: fadeInUp 1s ease-out 0.4s both;
}

.stat-item {
    text-align: center;
    transition: transform var(--transition-normal);
}

.stat-item:hover {
    transform: scale(1.1);
}

.stat-number {
    font-size: 2rem;
    font-weight: 800;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1;
    margin-bottom: 0.25rem;
    animation: zoomIn 0.6s ease-out;
}

.stat-label {
    font-size: 0.75rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    font-weight: 500;
}

.stat-divider {
    width: 1px;
    height: 40px;
    background: var(--glass-border);
    opacity: 0.5;
}

.site-header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--primary-gradient);
    opacity: 0.8;
    z-index: -1;
}

.site-header::after {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(255, 255, 255, 0.1) 0%, transparent 70%);
    animation: rotate 20s linear infinite;
    z-index: -1;
}

.site-header h1 {
    font-size: 3.5rem;
    font-weight: 800;
    margin-bottom: 1rem;
    background: linear-gradient(135deg, var(--neon-teal) 0%, var(--neon-pink) 50%, var(--neon-yellow) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    text-shadow: var(--neon-glow-teal);
    animation: fadeInScale 1s ease-out, neonPulse 2s ease-in-out infinite alternate;
    letter-spacing: -0.02em;
}

.tagline {
    font-size: 1.25rem;
    opacity: 0.95;
    font-weight: 400;
    color: var(--text-secondary);
    animation: fadeInUp 1s ease-out 0.2s both;
    text-shadow: var(--neon-glow-pink);
    letter-spacing: 0.05em;
}

/* Enhanced Search Container with Glassmorphism */
.search-container {
    max-width: 700px;
    margin: 3rem auto;
    padding: 0 1rem;
    position: relative;
    animation: fadeInUp 1s ease-out 0.4s both;
}

.search-wrapper {
    position: relative;
    display: flex;
    align-items: center;
    margin-bottom: 1rem;
}

.search-icon {
    position: absolute;
    left: 20px;
    color: var(--text-muted);
    pointer-events: none;
    z-index: 1;
    transition: all var(--transition-normal);
}

.search-wrapper:focus-within .search-icon {
    color: var(--neon-teal);
    transform: scale(1.1);
}

#searchInput {
    width: 100%;
    padding: 18px 60px 18px 50px;
    border: 2px solid var(--glass-border);
    border-radius: 20px;
    font-size: 1.1rem;
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    color: var(--text-primary);
    transition: all var(--transition-normal) cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: var(--shadow-md);
}

/* Search Filters */
.search-filters {
    display: flex;
    gap: 0.75rem;
    flex-wrap: wrap;
    justify-content: center;
    animation: fadeInUp 1s ease-out 0.5s both;
}

.filter-btn {
    padding: 0.6rem 1.2rem;
    border: 2px solid var(--glass-border);
    border-radius: 16px;
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    color: var(--text-secondary);
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-normal) cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;
}

.filter-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: var(--primary-gradient);
    opacity: 0;
    transition: opacity var(--transition-normal);
    z-index: -1;
}

.filter-btn:hover {
    border-color: var(--neon-teal);
    color: var(--neon-teal);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.filter-btn.active {
    background: var(--primary-gradient);
    border-color: transparent;
    color: white;
    box-shadow: var(--neon-glow-teal);
}

.filter-btn.active::before {
    opacity: 1;
}

.filter-btn:active {
    transform: translateY(0) scale(0.95);
}

#searchInput::placeholder {
    color: var(--text-muted);
}

#searchInput:focus {
    outline: none;
    border-color: var(--neon-teal);
    background: rgba(0, 206, 218, 0.1);
    box-shadow: var(--neon-glow-teal), var(--shadow-lg);
    transform: translateY(-2px);
}

.clear-btn {
    position: absolute;
    right: 1.5rem;
    top: 50%;
    transform: translateY(-50%);
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border: 1px solid var(--glass-border);
    font-size: 1.3rem;
    cursor: pointer;
    color: var(--text-secondary);
    padding: 8px 12px;
    border-radius: 12px;
    transition: all var(--transition-normal);
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.clear-btn:hover {
    background: var(--neon-pink);
    color: white;
    transform: translateY(-50%) scale(1.1);
    box-shadow: var(--neon-glow-pink), var(--shadow-md);
}

/* Main Content */
#mainContent {
    flex: 1;
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 1rem 3rem;
    width: 100%;
    position: relative;
}

/* Enhanced Subjects Grid with Advanced Animations */
.subjects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2.5rem;
    margin-top: 3rem;
    perspective: 1000px;
}

/* Enhanced Subject Button with 3D Effects and Animations */
.subject-button {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border: 2px solid var(--glass-border);
    border-radius: 24px;
    padding: 3rem 2rem;
    text-decoration: none;
    color: var(--text-primary);
    transition: all var(--transition-normal) cubic-bezier(0.4, 0, 0.2, 1);
    box-shadow: var(--shadow-lg);
    cursor: pointer;
    position: relative;
    overflow: hidden;
    min-height: 280px;
    transform-style: preserve-3d;
    animation: fadeInScale 0.8s ease-out both;
    transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.subject-button::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--primary-gradient);
    opacity: 0;
    transition: opacity var(--transition-normal);
    z-index: -1;
}

.subject-button::after {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: linear-gradient(45deg, transparent, rgba(255, 255, 255, 0.1), transparent);
    transform: rotate(45deg);
    transition: all var(--transition-slow);
    opacity: 0;
}

.subject-button:hover {
    transform: translateY(-8px) rotateX(5deg);
    box-shadow: var(--shadow-xl), var(--neon-glow-teal), var(--neon-glow-pink);
    border-color: var(--neon-teal);
}

.subject-button:hover::before {
    opacity: 0.8;
}

.subject-button:hover::after {
    animation: shimmer 0.6s ease-out;
}

.subject-button:active {
    transform: translateY(-4px) rotateX(2deg) scale(0.98);
}

.subject-button:nth-child(1) {
    animation-delay: 0.1s;
}

.subject-button:nth-child(2) {
    animation-delay: 0.2s;
}

.subject-button:nth-child(3) {
    animation-delay: 0.3s;
}

.subject-button:nth-child(4) {
    animation-delay: 0.4s;
}

.subject-icon {
    font-size: 4rem;
    margin-bottom: 1.5rem;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    filter: drop-shadow(0 4px 8px rgba(0, 206, 218, 0.5));
    transition: all var(--transition-normal) cubic-bezier(0.4, 0, 0.2, 1);
    animation: float 3s ease-in-out infinite, neonGlow 2s ease-in-out infinite alternate;
}

.subject-button:hover .subject-icon {
    transform: scale(1.2) rotateY(10deg);
    filter: drop-shadow(0 8px 16px rgba(255, 20, 147, 0.7));
}

.subject-name {
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--text-primary);
    text-align: center;
    margin-bottom: 0.75rem;
    letter-spacing: -0.01em;
    transition: all var(--transition-normal);
}

.subject-count {
    font-size: 1rem;
    color: var(--text-secondary);
    text-align: center;
    background: var(--glass-bg);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    border: 1px solid var(--glass-border);
    backdrop-filter: var(--glass-blur);
    transition: all var(--transition-normal);
}

.subject-button:hover .subject-count {
    background: rgba(255, 215, 0, 0.2);
    color: var(--neon-yellow);
    transform: scale(1.05);
    box-shadow: var(--neon-glow-yellow);
}

/* Enhanced Subject Pages */
.subject-container {
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border-radius: 24px;
    border: 2px solid var(--glass-border);
    box-shadow: var(--shadow-xl);
    overflow: hidden;
    margin-top: 2rem;
    animation: fadeInScale 0.8s ease-out;
}

.subject-header {
    background: var(--primary-gradient);
    color: white;
    padding: 2rem;
    display: flex;
    align-items: center;
    gap: 1.5rem;
    position: relative;
    overflow: hidden;
}

.subject-header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(45deg, transparent, rgba(255, 255, 255, 0.1), transparent);
    animation: shimmer 3s ease-in-out infinite;
}

.back-button {
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border: 2px solid var(--glass-border);
    color: white;
    padding: 12px 20px;
    border-radius: 16px;
    cursor: pointer;
    font-size: 1rem;
    text-decoration: none;
    transition: all var(--transition-normal);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 500;
    box-shadow: var(--shadow-md);
}

.back-button:hover {
    background: rgba(255, 255, 255, 0.2);
    transform: translateX(-4px);
    box-shadow: var(--shadow-lg);
}

.subject-title {
    font-size: 2rem;
    font-weight: 700;
    flex: 1;
    text-align: center;
    text-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
    letter-spacing: -0.02em;
}

/* Enhanced PDF List */
.pdf-list {
    padding: 2rem;
}

/* Enhanced PDF Items with Advanced Animations */
.pdf-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
    transition: all var(--transition-normal);
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border-radius: 16px;
    margin-bottom: 1rem;
    border: 1px solid var(--glass-border);
    position: relative;
    overflow: hidden;
    animation: slideInLeft 0.6s ease-out both;
}

/* PDF Grid Layout for Subject Pages */
.pdf-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 2rem;
    padding: 2rem;
}

.pdf-card {
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border: 1px solid var(--glass-border);
    border-radius: 16px;
    overflow: hidden;
    transition: all var(--transition-normal);
    animation: fadeInScale 0.6s ease-out both;
    position: relative;
}

.pdf-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--primary-gradient);
    opacity: 0;
    transition: opacity var(--transition-normal);
    z-index: -1;
}

.pdf-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-xl), var(--neon-glow-teal);
    border-color: var(--neon-teal);
}

.pdf-card:hover::before {
    opacity: 0.1;
}

.pdf-thumbnail {
    width: 100%;
    height: 200px;
    background: var(--surface);
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
}

.pdf-thumbnail-icon {
    font-size: 4rem;
    color: var(--neon-teal);
    text-shadow: var(--neon-glow-teal);
    animation: float 3s ease-in-out infinite;
    transition: all var(--transition-normal) cubic-bezier(0.4, 0, 0.2, 1);
}

.pdf-thumbnail::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, transparent, rgba(0, 206, 218, 0.1), transparent);
    animation: shimmer 3s ease-in-out infinite;
}

.pdf-card-content {
    padding: 1.5rem;
}

.pdf-card-title {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    line-height: 1.4;
}

.pdf-card-description {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
    line-height: 1.5;
}

.pdf-card-actions {
    display: flex;
    gap: 0.75rem;
}

.btn-view-card, .btn-download-card {
    flex: 1;
    padding: 10px 16px;
    border: none;
    border-radius: 12px;
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: 600;
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 44px;
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.btn-view-card {
    background: var(--primary-gradient);
    color: white;
}

.btn-view-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg), var(--shadow-glow);
}

.btn-download-card {
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    color: var(--text-primary);
    border: 2px solid var(--glass-border);
}

.btn-download-card:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-light);
}

/* Subject Header Enhancement */
.subject-info {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.subject-info .subject-icon {
    font-size: 2rem;
    margin-bottom: 0;
}

.pdf-count {
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border: 1px solid var(--glass-border);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-weight: 600;
    color: var(--neon-yellow);
    text-shadow: var(--neon-glow-yellow);
}

.pdf-item::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: var(--primary-gradient);
    transform: scaleY(0);
    transition: transform var(--transition-normal);
}

.pdf-item:hover {
    background: rgba(255, 255, 255, 0.15);
    transform: translateX(8px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-light);
}

.pdf-item:hover::before {
    transform: scaleY(1);
}

.pdf-item:last-child {
    border-bottom: none;
    margin-bottom: 0;
}

.pdf-info {
    flex: 1;
    margin-right: 2rem;
}

.pdf-title {
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    font-size: 1.1rem;
    letter-spacing: -0.01em;
}

.pdf-description {
    font-size: 0.95rem;
    color: var(--text-secondary);
    line-height: 1.5;
}

.pdf-actions {
    display: flex;
    gap: 1rem;
    flex-shrink: 0;
}

/* Enhanced Buttons with Advanced Animations */
.btn-view, .btn-download {
    padding: 12px 24px;
    border: none;
    border-radius: 16px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 48px;
    transition: all var(--transition-normal) cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    overflow: hidden;
    box-shadow: var(--shadow-md);
}

.btn-view::before, .btn-download::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(45deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transform: translateX(-100%);
    transition: transform var(--transition-slow);
}

.btn-view:hover::before, .btn-download:hover::before {
    transform: translateX(100%);
}

.btn-view {
    background: var(--primary-gradient);
    color: white;
}

.btn-view:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg), var(--shadow-glow);
}

.btn-download {
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    color: var(--text-primary);
    border: 2px solid var(--glass-border);
}

.btn-download:hover {
    background: var(--primary-color);
    color: white;
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-light);
}

/* Enhanced Search Results */
.search-results {
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border-radius: 24px;
    border: 2px solid var(--glass-border);
    box-shadow: var(--shadow-xl);
    margin-top: 2rem;
    animation: fadeInScale 0.8s ease-out;
}

.search-category {
    background: var(--surface);
    color: var(--primary-light);
    padding: 1.5rem 2rem;
    font-weight: 700;
    font-size: 1.2rem;
    border-bottom: 2px solid var(--primary-color);
    letter-spacing: -0.01em;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* Enhanced No Results Message */
.no-results {
    text-align: center;
    padding: 4rem 2rem;
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border-radius: 24px;
    border: 2px solid var(--glass-border);
    box-shadow: var(--shadow-lg);
    margin-top: 2rem;
    animation: fadeInScale 0.8s ease-out;
}

.no-results p {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

/* Enhanced Modal with Advanced Animations */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.85);
    backdrop-filter: blur(10px);
    display: none;
    justify-content: center;
    align-items: center;
    z-index: 1000;
    padding: 2rem;
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.modal.active {
    display: flex;
    opacity: 1;
    animation: fadeIn 0.3s ease-out;
}

.modal-content {
    background: var(--surface);
    width: 95%;
    max-width: 1200px;
    height: 90%;
    border-radius: 24px;
    position: relative;
    box-shadow: var(--shadow-xl), var(--neon-glow-teal), var(--neon-glow-pink);
    display: flex;
    flex-direction: column;
    border: 2px solid var(--neon-teal);
    backdrop-filter: var(--glass-blur);
    animation: slideUpScale 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.close-btn {
    position: absolute;
    top: 1.5rem;
    right: 1.5rem;
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border: 2px solid var(--glass-border);
    color: var(--text-primary);
    font-size: 1.5rem;
    cursor: pointer;
    padding: 12px;
    border-radius: 16px;
    z-index: 1001;
    transition: all var(--transition-normal);
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-md);
}

.close-btn:hover {
    background: var(--neon-pink);
    color: white;
    transform: rotate(90deg) scale(1.1);
    box-shadow: var(--neon-glow-pink), var(--shadow-lg);
}

/* PDF Controls */
.pdf-controls {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    padding: 1rem;
    background: var(--glass-bg);
    border-bottom: 1px solid var(--border-color);
    backdrop-filter: var(--glass-blur);
}

.pdf-nav-btn {
    background: var(--glass-bg);
    border: 2px solid var(--neon-teal);
    color: var(--neon-teal);
    padding: 0.5rem 1rem;
    border-radius: 12px;
    cursor: pointer;
    font-size: 1.2rem;
    font-weight: 600;
    transition: all var(--transition-normal);
    min-width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-md);
}

.pdf-nav-btn:hover {
    background: var(--neon-teal);
    color: var(--dark-metallic);
    transform: scale(1.1);
    box-shadow: var(--neon-glow-teal), var(--shadow-lg);
}

.pdf-nav-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
}

.page-info {
    color: var(--text-secondary);
    font-weight: 500;
    min-width: 120px;
    text-align: center;
    font-size: 0.9rem;
    text-shadow: var(--neon-glow-pink);
}

/* PDF Viewer Container */
.pdf-viewer-container {
    width: 100%;
    height: calc(100% - 80px);
    border-radius: 0 0 24px 24px;
    background: #1a1a1a;
    overflow: auto;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
}

.pdf-viewer-container canvas {
    max-width: 100%;
    max-height: 100%;
    box-shadow: var(--shadow-lg);
}

.pdf-loading {
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    gap: 1rem;
    color: var(--text-secondary);
}

.pdf-loading-spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--border-color);
    border-top: 3px solid var(--neon-teal);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

.pdf-error {
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    gap: 1rem;
    color: var(--neon-pink);
    text-align: center;
    padding: 2rem;
}

.pdf-error-icon {
    font-size: 3rem;
    animation: pulse 2s ease-in-out infinite;
}

/* Enhanced Footer */
.site-footer {
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border-top: 1px solid var(--glass-border);
    color: var(--text-secondary);
    text-align: center;
    padding: 2rem;
    margin-top: auto;
    box-shadow: 0 -4px 20px rgba(0, 0, 0, 0.1);
}

.site-footer p {
    opacity: 0.9;
    font-size: 1rem;
}

/* Advanced Animations */
@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeInScale {
    from {
        opacity: 0;
        transform: scale(0.9);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-50px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes slideUpScale {
    from {
        opacity: 0;
        transform: translateY(30px) scale(0.9);
    }
    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

@keyframes slideInLeft {
    from {
        opacity: 0;
        transform: translateX(-30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes float {
    0%, 100% {
        transform: translateY(0);
    }
    50% {
        transform: translateY(-10px);
    }
}

@keyframes shimmer {
    0% {
        transform: translateX(-100%) rotate(45deg);
        opacity: 0;
    }
    50% {
        opacity: 1;
    }
    100% {
        transform: translateX(100%) rotate(45deg);
        opacity: 0;
    }
}

@keyframes rotate {
    from {
        transform: rotate(0deg);
    }
    to {
        transform: rotate(360deg);
    }
}

@keyframes pulse {
    0%, 100% {
        transform: scale(1);
        opacity: 1;
    }
    50% {
        transform: scale(1.05);
        opacity: 0.8;
    }
}

@keyframes neonPulse {
    0%, 100% {
        text-shadow: var(--neon-glow-teal);
    }
    50% {
        text-shadow: var(--neon-glow-pink);
    }
}

@keyframes neonGlow {
    0%, 100% {
        filter: drop-shadow(0 4px 8px rgba(0, 206, 218, 0.5));
    }
    50% {
        filter: drop-shadow(0 8px 16px rgba(255, 20, 147, 0.7));
    }
}

@keyframes spin {
    0% {
        transform: rotate(0deg);
    }
    100% {
        transform: rotate(360deg);
    }
}

/* Enhanced Loading Skeleton Animation */
.loading-skeleton {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 400px;
    margin-top: 3rem;
}

.skeleton-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2.5rem;
    width: 100%;
    max-width: 1000px;
}

.skeleton-item {
    height: 280px;
    border-radius: 24px;
    background: var(--glass-bg);
    backdrop-filter: var(--glass-blur);
    border: 2px solid var(--glass-border);
    position: relative;
    overflow: hidden;
}

.skeleton-item::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(90deg,
        var(--surface) 0%,
        var(--surface-light) 25%,
        var(--surface) 50%,
        var(--surface-light) 75%,
        var(--surface) 100%);
    background-size: 200% 100%;
    animation: shimmer 1.5s ease-in-out infinite;
    border-radius: 22px;
}

.skeleton {
    background: linear-gradient(90deg, var(--surface) 25%, var(--surface-light) 50%, var(--surface) 75%);
    background-size: 200% 100%;
    animation: loading 1.5s infinite;
    border-radius: 8px;
}

@keyframes loading {
    0% {
        background-position: 200% 0;
    }
    100% {
        background-position: -200% 0;
    }
}

/* Enhanced Responsive Design */

/* Tablet Styles (768px and below) */
@media (max-width: 768px) {
    .site-header h1 {
        font-size: 2.5rem;
    }

    .tagline {
        font-size: 1.1rem;
    }
    
    .stats-bar {
        gap: 1rem;
        padding: 1rem;
    }
    
    .stat-number {
        font-size: 1.5rem;
    }
    
    .stat-label {
        font-size: 0.65rem;
    }
    
    .search-filters {
        gap: 0.5rem;
    }
    
    .filter-btn {
        padding: 0.5rem 1rem;
        font-size: 0.85rem;
    }
    
    .fab-container {
        bottom: 1.5rem;
        right: 1.5rem;
    }
    
    .fab {
        width: 48px;
        height: 48px;
    }

    .search-container {
        margin: 2rem auto;
    }

    #mainContent {
        padding: 0 1rem 2rem;
    }

    .subjects-grid {
        grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
        gap: 2rem;
        margin-top: 2rem;
    }

    .subject-button {
        padding: 2rem 1.5rem;
        min-height: 220px;
    }

    .subject-icon {
        font-size: 3rem;
        margin-bottom: 1rem;
    }

    .subject-name {
        font-size: 1.5rem;
    }

    .pdf-item {
        padding: 1.25rem;
        flex-direction: column;
        align-items: stretch;
        gap: 1rem;
    }

    .pdf-info {
        margin-right: 0;
    }

    .pdf-actions {
        justify-content: center;
        gap: 1rem;
    }

    .btn-view, .btn-download {
        flex: 1;
        padding: 14px 20px;
    }

    .modal-content {
        width: 95%;
        height: 95%;
    }

    /* PDF Grid Tablet Styles */
    .pdf-grid {
        grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
        gap: 1.5rem;
        padding: 1.5rem;
    }

    .pdf-thumbnail {
        height: 180px;
    }

    .pdf-thumbnail-icon {
        font-size: 3.5rem;
    }
}

/* Mobile Styles (480px and below) */
@media (max-width: 480px) {
    .site-header {
        padding: 2rem 1rem;
    }

    .site-header h1 {
        font-size: 2rem;
    }
    
    .header-badge {
        padding: 0.4rem 0.8rem;
        font-size: 0.75rem;
    }
    
    .badge-pulse {
        width: 6px;
        height: 6px;
    }
    
    .stats-bar {
        flex-direction: column;
        gap: 1rem;
        padding: 1rem;
    }
    
    .stat-divider {
        width: 100%;
        height: 1px;
    }
    
    .stat-number {
        font-size: 1.8rem;
    }
    
    .search-filters {
        gap: 0.5rem;
    }
    
    .filter-btn {
        padding: 0.5rem 0.8rem;
        font-size: 0.8rem;
    }
    
    .fab-container {
        bottom: 1rem;
        right: 1rem;
        gap: 0.75rem;
    }
    
    .fab {
        width: 44px;
        height: 44px;
    }

    .search-container {
        margin: 1.5rem auto;
        padding: 0 0.5rem;
    }

    #searchInput {
        padding: 16px 50px 16px 45px;
        font-size: 1rem;
    }
    
    .search-icon {
        left: 16px;
        width: 18px;
        height: 18px;
    }

    #mainContent {
        padding: 0 0.5rem 1.5rem;
    }

    .subjects-grid {
        grid-template-columns: 1fr;
        gap: 1.5rem;
        margin-top: 1.5rem;
    }

    .subject-button {
        padding: 2rem 1.25rem;
        min-height: 180px;
    }

    .subject-icon {
        font-size: 2.5rem;
        margin-bottom: 0.75rem;
    }

    .subject-name {
        font-size: 1.3rem;
    }

    .subject-count {
        font-size: 0.9rem;
    }

    .pdf-item {
        padding: 1rem;
    }

    .pdf-title {
        font-size: 1rem;
    }

    .pdf-description {
        font-size: 0.9rem;
    }

    .btn-view, .btn-download {
        padding: 16px 16px;
        font-size: 0.95rem;
        min-height: 52px;
    }

    .close-btn {
        top: 1rem;
        right: 1rem;
        width: 40px;
        height: 40px;
    }

    .no-results {
        padding: 3rem 1.5rem;
    }

    .subject-header {
        padding: 1.5rem;
        flex-direction: column;
        gap: 1rem;
    }

    .subject-title {
        font-size: 1.5rem;
    }

    .back-button {
        align-self: flex-start;
    }

    /* PDF Grid Mobile Styles */
    .pdf-grid {
        grid-template-columns: 1fr;
        gap: 1.5rem;
        padding: 1rem;
    }

    .pdf-thumbnail {
        height: 150px;
    }

    .pdf-thumbnail-icon {
        font-size: 3rem;
    }

    .pdf-card-content {
        padding: 1rem;
    }

    .pdf-card-title {
        font-size: 1rem;
    }

    .pdf-card-description {
        font-size: 0.85rem;
    }

    .btn-view-card, .btn-download-card {
        padding: 12px 16px;
        font-size: 0.9rem;
    }

    .subject-info {
        flex-direction: column;
        gap: 0.5rem;
        text-align: center;
    }
}

/* Large Desktop Styles (1200px and above) */
@media (min-width: 1200px) {
    .site-header h1 {
        font-size: 4rem;
    }

    .subjects-grid {
        grid-template-columns: repeat(2, 1fr);
        max-width: 1000px;
        margin: 3rem auto 0;
        gap: 3rem;
    }

    .subject-button {
        min-height: 320px;
        padding: 3.5rem 2.5rem;
    }

    .subject-icon {
        font-size: 4.5rem;
        margin-bottom: 2rem;
    }

    .subject-name {
        font-size: 2rem;
    }

    .pdf-list {
        padding: 2.5rem;
    }

    .pdf-item {
        padding: 1.75rem;
    }
}

/* Ultra-wide Desktop Styles (1600px and above) */
@media (min-width: 1600px) {
    .subjects-grid {
        grid-template-columns: repeat(2, 1fr);
        max-width: 1200px;
        gap: 3.5rem;
    }

    .subject-button {
        min-height: 360px;
        padding: 4rem 3rem;
    }
}

/* Enhanced Focus Styles for Accessibility */
.subject-button:focus-visible,
.btn-view:focus-visible,
.btn-download:focus-visible,
#searchInput:focus-visible,
.clear-btn:focus-visible,
.close-btn:focus-visible,
.back-button:focus-visible,
.pdf-nav-btn:focus-visible {
    outline: 3px solid var(--neon-teal);
    outline-offset: 3px;
    box-shadow: 0 0 0 6px rgba(0, 206, 218, 0.3);
}

/* Additional Professional Transitions */

/* Smooth Page Transitions */
@keyframes pageEnter {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Bounce Animation for Interactive Elements */
@keyframes bounceIn {
    0% {
        opacity: 0;
        transform: scale(0.3);
    }
    50% {
        opacity: 1;
        transform: scale(1.05);
    }
    70% {
        transform: scale(0.9);
    }
    100% {
        transform: scale(1);
    }
}

/* Slide from Right */
@keyframes slideInRight {
    from {
        opacity: 0;
        transform: translateX(30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

/* Zoom In Animation */
@keyframes zoomIn {
    from {
        opacity: 0;
        transform: scale(0.8);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

/* Flip Animation */
@keyframes flipIn {
    from {
        transform: perspective(400px) rotateY(90deg);
        opacity: 0;
    }
    to {
        transform: perspective(400px) rotateY(0);
        opacity: 1;
    }
}

/* Glow Pulse */
@keyframes glowPulse {
    0%, 100% {
        box-shadow: var(--shadow-md);
    }
    50% {
        box-shadow: var(--shadow-xl), var(--neon-glow-teal);
    }
}

/* Wave Animation */
@keyframes wave {
    0%, 100% {
        transform: rotate(0deg);
    }
    25% {
        transform: rotate(-10deg);
    }
    75% {
        transform: rotate(10deg);
    }
}

/* Heartbeat */
@keyframes heartbeat {
    0%, 100% {
        transform: scale(1);
    }
    10%, 30% {
        transform: scale(0.9);
    }
    20%, 40%, 60%, 80% {
        transform: scale(1.1);
    }
    50%, 70% {
        transform: scale(1.05);
    }
}

/* Shake Animation */
@keyframes shake {
    0%, 100% {
        transform: translateX(0);
    }
    10%, 30%, 50%, 70%, 90% {
        transform: translateX(-5px);
    }
    20%, 40%, 60%, 80% {
        transform: translateX(5px);
    }
}

/* PDF Viewer Iframe Styles */
.pdf-viewer-iframe {
    width: 100%;
    height: calc(100% - 80px);
    border: none;
    border-radius: 0 0 24px 24px;
    background: #1a1a1a;
    transition: opacity var(--transition-normal);
}

/* Modal Download Button */
.btn-download-modal {
    background: var(--primary-gradient);
    color: white;
    padding: 0.75rem 1.5rem;
    border-radius: 12px;
    text-decoration: none;
    font-weight: 600;
    transition: all var(--transition-normal);
    box-shadow: var(--shadow-md);
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
}

.btn-download-modal:hover {
    transform: translateY(-2px) scale(1.05);
    box-shadow: var(--shadow-lg), var(--neon-glow-pink);
    animation: glowPulse 1.5s ease-in-out infinite;
}

/* Stagger Animation Utility Classes */
.stagger-1 { animation-delay: 0.1s !important; }
.stagger-2 { animation-delay: 0.2s !important; }
.stagger-3 { animation-delay: 0.3s !important; }
.stagger-4 { animation-delay: 0.4s !important; }
.stagger-5 { animation-delay: 0.5s !important; }
.stagger-6 { animation-delay: 0.6s !important; }
.stagger-7 { animation-delay: 0.7s !important; }
.stagger-8 { animation-delay: 0.8s !important; }

/* Transition Enhancement Classes */
.smooth-transition {
    transition: all var(--transition-normal) cubic-bezier(0.4, 0, 0.2, 1);
}

.bounce-transition {
    transition: all var(--transition-bounce) cubic-bezier(0.68, -0.55, 0.265, 1.55);
}

.fast-transition {
    transition: all var(--transition-fast) ease-out;
}

.slow-transition {
    transition: all var(--transition-slow) ease-in-out;
}

/* Hover Effects */
.hover-lift:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
}

.hover-glow:hover {
    box-shadow: var(--shadow-xl), var(--neon-glow-teal), var(--neon-glow-pink);
}

.hover-scale:hover {
    transform: scale(1.05);
}

.hover-rotate:hover {
    transform: rotate(5deg);
}

/* Light Theme (Optional) */
body.light-theme {
    --background: #f5f5f5;
    --surface: #ffffff;
    --surface-light: #fafafa;
    --text-primary: #1a1a1a;
    --text-secondary: #333333;
    --text-muted: #666666;
    --glass-bg: rgba(255, 255, 255, 0.9);
    --glass-border: rgba(0, 206, 218, 0.2);
    --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
}

body.light-theme .site-header::before {
    opacity: 0.9;
}

body.light-theme .subject-button,
body.light-theme .pdf-card,
body.light-theme .search-results,
body.light-theme .no-results {
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
}

/* Print Styles */
@media print {
    .site-header,
    .search-container,
    .pdf-actions,
    .site-footer,
    .modal {
        display: none !important;
    }

    .subject-button {
        break-inside: avoid;
        page-break-inside: avoid;
        background: white !important;
        border: 1px solid #000 !important;
        color: #000 !important;
    }

    .pdf-item {
        border: 1px solid #000;
        margin-bottom: 0.5rem;
        page-break-inside: avoid;
        background: white !important;
        color: #000 !important;
    }
}