/* General Styles */
body {
    font-family: 'Segoe UI', Arial, sans-serif;
    background: #f6f8fa;
    margin: 0;
    color: #222;
    overflow-x: hidden;
}

/* --- Animation Keyframes --- */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

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

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

@keyframes scaleIn {
    from {
        opacity: 0;
        transform: scale(0.8);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

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

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

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

@keyframes gradientShift {
    0% {
        background-position: 0% 50%;
    }
    50% {
        background-position: 100% 50%;
    }
    100% {
        background-position: 0% 50%;
    }
}

@keyframes typing {
    from {
        width: 0;
    }
    to {
        width: 100%;
    }
}

@keyframes blink {
    0%, 50% {
        border-color: transparent;
    }
    51%, 100% {
        border-color: #4f8cff;
    }
}

@keyframes shimmer-move {
    0% {
        left: -100%;
    }
    100% {
        left: 100%;
    }
}

/* --- Animation Classes --- */
.animate-fade-in-up {
    animation: fadeInUp 0.8s ease-out;
}

.animate-fade-in-left {
    animation: fadeInLeft 0.8s ease-out;
}

.animate-fade-in-right {
    animation: fadeInRight 0.8s ease-out;
}

.animate-scale-in {
    animation: scaleIn 0.6s ease-out;
}

.animate-slide-in-top {
    animation: slideInFromTop 0.8s ease-out;
}

.animate-pulse {
    animation: pulse 2s infinite;
}

.animate-float {
    animation: float 3s ease-in-out infinite;
}

.animate-gradient {
    background: linear-gradient(-45deg, #4f8cff, #3461a4, #2ecc71, #27ae60);
    background-size: 400% 400%;
    animation: gradientShift 3s ease infinite;
}

/* --- Scroll-triggered animations --- */
.scroll-animate {
    opacity: 0;
    transform: translateY(30px);
    transition: all 0.8s ease-out;
}

.scroll-animate.animate {
    opacity: 1;
    transform: translateY(0);
}

/* --- Modern Capsule Navbar --- */
.navbar {
    position: fixed;
    top: 20px;
    left: 0;
    right: 0;
    margin: 0 auto;
    z-index: 1000;
    width: 100%;
    max-width: none;
    animation: slideInFromTop 0.8s ease-out;
    display: flex;
    justify-content: center;
    align-items: center;
}

.nav-container {
    margin: 0 auto;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-radius: 50px;
    padding: 0.8rem 2.7rem;
    display: flex;
    align-items: center;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
    transition: all 0.3s ease;
    position: relative;
    width: 100%;
    max-width: 1150px;
}

.nav-container:hover {
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.15);
}

.nav-logo {
    flex: 0 0 auto;
    font-size: 1.5rem;
    font-weight: bold;
    letter-spacing: 1px;
    color: #2d3e50;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: all 0.3s ease;
    z-index: 2;
    margin-right: 2rem;
}

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

.nav-logo i {
    color: #4f8cff;
    animation: float 3s ease-in-out infinite;
}

.nav-links {
    list-style: none;
    display: flex;
    flex: 1 1 0;
    justify-content: center;
    gap: 2rem;
    margin: 0;
    padding: 0;
    position: static;
    left: auto;
    transform: none;
    top: auto;
    translate: none;
    z-index: 1;
}

.nav-links li a {
    color: #2d3e50;
    text-decoration: none;
    font-size: 0.95rem;
    font-weight: 500;
    transition: all 0.3s ease;
    padding: 0.5rem 1rem;
    border-radius: 25px;
    position: relative;
    overflow: hidden;
}

.nav-links li a::before, .nav-links li a:hover::before {
    display: none !important;
}

.nav-links li a:hover {
    background: rgba(79, 140, 255, 0.08);
    color: #4f8cff;
    border-radius: 25px;
    transition: background 0.2s, color 0.2s;
}

/* --- Parallax Hero --- */
.parallax-hero {
    min-height: 100vh;
    background-image: url('https://images.unsplash.com/photo-1522202176988-66273c2fd55f?auto=format&fit=crop&w=1200&q=80');
    background-attachment: fixed;
    background-size: cover;
    background-position: center;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    margin-bottom: 0;
}

.parallax-hero::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background: linear-gradient(135deg, rgba(44,62,80,0.8), rgba(79,140,255,0.6));
    z-index: 1;
}

.hero-content {
    position: relative;
    z-index: 2;
    color: #fff;
    text-align: center;
    padding: 2rem 1rem;
    max-width: 800px;
    animation: fadeInUp 1s ease-out;
}

.hero-badge {
    background: rgba(255, 255, 255, 0.2);
    backdrop-filter: blur(10px);
    border-radius: 25px;
    padding: 0.5rem 1.5rem;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    font-weight: 500;
    margin-bottom: 2rem;
    border: 1px solid rgba(255, 255, 255, 0.3);
    animation: scaleIn 0.8s ease-out 0.3s both;
}

.hero-badge i {
    color: #ffd700;
    animation: pulse 2s infinite;
}

.gradient-text {
    background: linear-gradient(135deg, #4f8cff, #ff6b6b);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    background-size: 200% 200%;
    animation: gradientShift 3s ease infinite;
    display: inline-block;
}

.hero-content h1 {
    font-size: 3.5rem;
    margin-bottom: 1.5rem;
    letter-spacing: 2px;
    font-weight: 700;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
    line-height: 1.2;
    animation: fadeInUp 1s ease-out 0.5s both;
}

.hero-content p {
    font-size: 1.3rem;
    margin-bottom: 2.5rem;
    opacity: 0.95;
    line-height: 1.6;
    animation: fadeInUp 1s ease-out 0.7s both;
}

.hero-buttons {
    display: flex;
    gap: 1rem;
    justify-content: center;
    margin-bottom: 3rem;
    flex-wrap: wrap;
    animation: fadeInUp 1s ease-out 0.9s both;
}

.cta-btn {
    border: none;
    border-radius: 50px;
    padding: 1rem 2rem;
    font-size: 1.1rem;
    cursor: pointer;
    text-decoration: none;
    transition: all 0.3s ease;
    font-weight: 600;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    position: relative;
    overflow: hidden;
}

.cta-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 ease;
}

.cta-btn:hover::before {
    left: 100%;
}

.cta-btn.primary {
    background: linear-gradient(135deg, #4f8cff, #3461a4);
    color: #fff;
    box-shadow: 0 8px 25px rgba(79, 140, 255, 0.3);
}

.cta-btn.secondary {
    background: rgba(255, 255, 255, 0.2);
    color: #fff;
    border: 2px solid rgba(255, 255, 255, 0.3);
    backdrop-filter: blur(10px);
}

.cta-btn:hover {
    transform: translateY(-3px) scale(1.05);
}

.cta-btn.primary:hover {
    box-shadow: 0 12px 35px rgba(79, 140, 255, 0.4);
}

.cta-btn.secondary:hover {
    background: rgba(255, 255, 255, 0.3);
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 3rem;
    flex-wrap: wrap;
    animation: fadeInUp 1s ease-out 1.1s both;
}

.stat-item {
    text-align: center;
    transition: all 0.3s ease;
}

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

.stat-number {
    display: block;
    font-size: 2.5rem;
    font-weight: 700;
    color: #ffd700;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
    animation: pulse 2s infinite;
}

.stat-label {
    font-size: 0.9rem;
    opacity: 0.9;
    font-weight: 500;
}

/* --- Section Headers --- */
.section-header {
    text-align: center;
    margin-bottom: 3rem;
    animation: fadeInUp 0.8s ease-out;
}

.section-header h2 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
    color: #2d3e50;
    font-weight: 700;
    position: relative;
}

.section-header h2::after {
    content: '';
    position: absolute;
    bottom: -10px;
    left: 50%;
    transform: translateX(-50%);
    width: 60px;
    height: 3px;
    background: linear-gradient(135deg, #4f8cff, #3461a4);
    border-radius: 2px;
    animation: scaleIn 0.8s ease-out 0.5s both;
}

.section-header p {
    font-size: 1.1rem;
    color: #666;
    max-width: 600px;
    margin: 0 auto;
    line-height: 1.6;
}

/* --- Main Content --- */
main {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    background: transparent;
    box-shadow: none;
    border-radius: 0;
}

/* --- Subjects Section --- */
.subjects-section {
    margin: 4rem 0;
    padding: 3rem 0;
}

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

.subject-btn {
    background: linear-gradient(135deg, #4f8cff, #3461a4);
    color: #fff;
    border: none;
    border-radius: 20px;
    padding: 2rem 1.5rem;
    font-size: 1.3rem;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 8px 25px rgba(79, 140, 255, 0.2);
    font-weight: 600;
    min-height: 120px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    position: relative;
    overflow: hidden;
}

.subject-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 ease;
}

.subject-btn:hover::before {
    left: 100%;
}

.subject-btn i {
    font-size: 2rem;
    opacity: 0.9;
    transition: all 0.3s ease;
}

.subject-btn:hover {
    transform: translateY(-8px) scale(1.05);
    box-shadow: 0 20px 40px rgba(79, 140, 255, 0.3);
}

.subject-btn:hover i {
    transform: rotate(360deg) scale(1.2);
}

/* --- Features Section --- */
.features-section {
    margin: 4rem 0;
    padding: 3rem 0;
    background: rgba(255, 255, 255, 0.8);
    border-radius: 30px;
    backdrop-filter: blur(10px);
}

.features-list {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    margin-top: 2rem;
    padding: 0 2rem;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

.feature-card {
    background: #fff;
    border-radius: 20px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    padding: 2rem 1.5rem;
    text-align: center;
    transition: all 0.3s ease;
    border: 1px solid rgba(255, 255, 255, 0.2);
    position: relative;
    overflow: hidden;
}

.feature-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, rgba(79, 140, 255, 0.1), rgba(46, 204, 113, 0.1));
    opacity: 0;
    transition: opacity 0.3s ease;
}

.feature-card:hover::before {
    opacity: 1;
}

.feature-card:hover {
    transform: translateY(-8px) scale(1.02);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.15);
}

.feature-icon {
    width: 60px;
    height: 60px;
    background: linear-gradient(135deg, #4f8cff, #3461a4);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 1.5rem;
    color: #fff;
    font-size: 1.5rem;
    transition: all 0.3s ease;
    position: relative;
    z-index: 1;
}

.feature-card:hover .feature-icon {
    transform: rotate(360deg) scale(1.1);
    animation: pulse 1s infinite;
}

.feature-card h3 {
    margin-top: 0;
    color: #2d3e50;
    font-size: 1.3rem;
    font-weight: 600;
    margin-bottom: 1rem;
    position: relative;
    z-index: 1;
}

.feature-card p {
    color: #666;
    line-height: 1.6;
    position: relative;
    z-index: 1;
}

/* --- Stats Section --- */
.stats-section {
    margin: 4rem 0;
    padding: 3rem 0;
}

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

.stat-card {
    background: rgba(255, 255, 255, 0.9);
    border-radius: 20px;
    padding: 2rem;
    text-align: center;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    backdrop-filter: blur(10px);
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 1.5rem;
    position: relative;
    overflow: hidden;
}

.stat-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(79, 140, 255, 0.1), transparent);
    transition: left 0.5s ease;
}

.stat-card:hover::before {
    left: 100%;
}

.stat-card:hover {
    transform: translateY(-5px) scale(1.02);
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.15);
}

.stat-icon {
    width: 60px;
    height: 60px;
    background: linear-gradient(135deg, #4f8cff, #3461a4);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-size: 1.5rem;
    flex-shrink: 0;
    transition: all 0.3s ease;
}

.stat-card:hover .stat-icon {
    transform: rotate(360deg) scale(1.1);
    animation: pulse 1s infinite;
}

.stat-content h3 {
    font-size: 2rem;
    margin: 0 0 0.5rem 0;
    color: #2d3e50;
    font-weight: 700;
    transition: all 0.3s ease;
}

.stat-card:hover .stat-content h3 {
    color: #4f8cff;
    transform: scale(1.1);
}

.stat-content p {
    margin: 0;
    color: #666;
    font-weight: 500;
}

/* --- Revision Section --- */
.revision-section {
    margin: 4rem 0;
    background: rgba(255, 255, 255, 0.9);
    border-radius: 30px;
    padding: 3rem 2rem;
    backdrop-filter: blur(10px);
}

#revision-section.hidden {
    display: none;
}

#topics-list {
    margin: 2rem 0;
}

.topic {
    background: #fff;
    border-radius: 15px;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.08);
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.topic::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(79, 140, 255, 0.1), transparent);
    transition: left 0.5s ease;
}

.topic:hover::before {
    left: 100%;
}

.topic:hover {
    transform: translateX(8px) scale(1.02);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.12);
}

.topic-info {
    flex: 1;
}

.topic-title {
    font-weight: 600;
    margin-bottom: 0.5rem;
    font-size: 1.1rem;
    color: #2d3e50;
    transition: color 0.3s ease;
}

.topic:hover .topic-title {
    color: #4f8cff;
}

.topic-summary {
    font-size: 1rem;
    color: #666;
    line-height: 1.5;
}

.mark-btn {
    background: linear-gradient(135deg, #2ecc71, #27ae60);
    color: #fff;
    border: none;
    border-radius: 25px;
    padding: 0.8rem 1.5rem;
    font-size: 1rem;
    cursor: pointer;
    transition: all 0.3s ease;
    margin-left: 1rem;
    font-weight: 500;
    position: relative;
    overflow: hidden;
}

.mark-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 ease;
}

.mark-btn:hover::before {
    left: 100%;
}

.mark-btn:hover {
    transform: scale(1.05);
    box-shadow: 0 5px 15px rgba(46, 204, 113, 0.3);
}

.mark-btn:disabled {
    background: #b2dfb2;
    cursor: default;
}

#progress {
    font-size: 1.2rem;
    margin-bottom: 2rem;
    color: #4f8cff;
    font-weight: 600;
    text-align: center;
    animation: pulse 2s infinite;
}

#back-btn {
    background: linear-gradient(135deg, #e74c3c, #c0392b);
    color: #fff;
    border: none;
    border-radius: 25px;
    padding: 1rem 2rem;
    font-size: 1.1rem;
    cursor: pointer;
    transition: all 0.3s ease;
    margin-top: 1rem;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    position: relative;
    overflow: hidden;
}

#back-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 ease;
}

#back-btn:hover::before {
    left: 100%;
}

#back-btn:hover {
    transform: translateY(-2px) scale(1.05);
    box-shadow: 0 8px 25px rgba(231, 76, 60, 0.3);
}

/* --- Testimonials Section --- */
.testimonials-section {
    margin: 4rem 0;
    padding: 3rem 0;
}

.testimonials-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
}

.testimonial {
    background: rgba(255, 255, 255, 0.9);
    border-radius: 20px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
    padding: 2rem 1.5rem;
    backdrop-filter: blur(10px);
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.testimonial::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, rgba(79, 140, 255, 0.05), rgba(46, 204, 113, 0.05));
    opacity: 0;
    transition: opacity 0.3s ease;
}

.testimonial:hover::before {
    opacity: 1;
}

.testimonial:hover {
    transform: translateY(-8px) scale(1.02);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.15);
}

.testimonial-rating {
    margin-bottom: 1rem;
}

.testimonial-rating i {
    color: #ffd700;
    margin-right: 0.2rem;
    transition: all 0.3s ease;
}

.testimonial:hover .testimonial-rating i {
    transform: scale(1.2);
    animation: pulse 0.5s ease;
}

.testimonial p {
    font-style: italic;
    color: #555;
    line-height: 1.6;
    margin-bottom: 1.5rem;
    position: relative;
    z-index: 1;
}

.testimonial-author {
    display: flex;
    align-items: center;
    gap: 1rem;
    position: relative;
    z-index: 1;
}

.testimonial-author img {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    object-fit: cover;
    transition: all 0.3s ease;
}

.testimonial:hover .testimonial-author img {
    transform: scale(1.1);
}

.author-name {
    display: block;
    font-weight: 600;
    color: #2d3e50;
    transition: color 0.3s ease;
}

.testimonial:hover .author-name {
    color: #4f8cff;
}

.author-title {
    display: block;
    font-size: 0.9rem;
    color: #666;
}

/* --- Contact Section --- */
.contact-section {
    margin: 4rem 0 2rem 0;
    padding: 3rem 0;
    background: rgba(255, 255, 255, 0.8);
    border-radius: 30px;
    backdrop-filter: blur(10px);
}

.contact-container {
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: 3rem;
    margin-top: 2rem;
}

.contact-info {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.contact-item {
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1.5rem;
    background: #fff;
    border-radius: 15px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.08);
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
}

.contact-item::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(79, 140, 255, 0.1), transparent);
    transition: left 0.5s ease;
}

.contact-item:hover::before {
    left: 100%;
}

.contact-item:hover {
    transform: translateX(5px) scale(1.02);
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.12);
}

.contact-item i {
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, #4f8cff, #3461a4);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    font-size: 1.1rem;
    transition: all 0.3s ease;
    position: relative;
    z-index: 1;
}

.contact-item:hover i {
    transform: rotate(360deg) scale(1.1);
    animation: pulse 1s infinite;
}

.contact-item h4 {
    margin: 0 0 0.3rem 0;
    color: #2d3e50;
    font-weight: 600;
    position: relative;
    z-index: 1;
}

.contact-item p {
    margin: 0;
    color: #666;
    position: relative;
    z-index: 1;
}

#contact-form {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.form-group {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

#contact-form input, #contact-form textarea {
    padding: 1rem;
    border-radius: 15px;
    border: 2px solid #e1e8ed;
    font-size: 1rem;
    resize: none;
    transition: all 0.3s ease;
    background: #fff;
}

#contact-form input:focus, #contact-form textarea:focus {
    outline: none;
    border-color: #4f8cff;
    transform: scale(1.02);
    box-shadow: 0 5px 15px rgba(79, 140, 255, 0.2);
}

#contact-form button {
    background: linear-gradient(135deg, #4f8cff, #3461a4);
    color: #fff;
    border: none;
    border-radius: 25px;
    padding: 1rem 0;
    font-size: 1.1rem;
    cursor: pointer;
    transition: all 0.3s ease;
    font-weight: 600;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    position: relative;
    overflow: hidden;
}

#contact-form button::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 ease;
}

#contact-form button:hover::before {
    left: 100%;
}

#contact-form button:hover {
    transform: translateY(-2px) scale(1.02);
    box-shadow: 0 8px 25px rgba(79, 140, 255, 0.3);
}

#contact-success {
    color: #2ecc71;
    margin-top: 1rem;
    font-weight: 600;
    font-size: 1.1rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    animation: scaleIn 0.5s ease-out;
}

/* --- Footer --- */
footer {
    background: #2d3e50;
    color: #fff;
    margin-top: 4rem;
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 3rem 2rem 2rem;
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 3rem;
}

.footer-logo {
    font-size: 1.5rem;
    font-weight: bold;
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    transition: all 0.3s ease;
}

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

.footer-logo i {
    color: #4f8cff;
    animation: float 3s ease-in-out infinite;
}

.footer-section p {
    color: #bdc3c7;
    line-height: 1.6;
    margin-bottom: 1.5rem;
}

.social-links {
    display: flex;
    gap: 1rem;
}

.social-links a {
    width: 40px;
    height: 40px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    text-decoration: none;
    transition: all 0.3s ease;
}

.social-links a:hover {
    background: #4f8cff;
    transform: translateY(-3px) scale(1.1);
}

.footer-section h4 {
    margin-bottom: 1rem;
    color: #fff;
    font-weight: 600;
}

.footer-section ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

.footer-section ul li {
    margin-bottom: 0.5rem;
}

.footer-section ul li a {
    color: #bdc3c7;
    text-decoration: none;
    transition: all 0.3s ease;
}

.footer-section ul li a:hover {
    color: #4f8cff;
    transform: translateX(5px);
}

.footer-bottom {
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    padding: 1.5rem 2rem;
    text-align: center;
    color: #bdc3c7;
}

/* --- Responsive --- */
@media (max-width: 768px) {
    .navbar {
        top: 10px;
        width: 95%;
    }
    
    .nav-container {
        flex-direction: column;
        gap: 1rem;
        padding: 1rem;
    }
    
    .nav-links {
        gap: 1rem;
        flex-wrap: wrap;
        justify-content: center;
    }
    
    .hero-content h1 {
        font-size: 2.5rem;
    }
    
    .hero-content p {
        font-size: 1.2rem;
    }
    
    .hero-buttons {
        flex-direction: column;
        align-items: center;
    }
    
    .hero-stats {
        gap: 2rem;
    }
    
    .subjects {
        grid-template-columns: 1fr;
    }
    
    .features-list {
        grid-template-columns: 1fr;
    }
    
    .stats-grid {
        grid-template-columns: 1fr;
    }
    
    .testimonials-list {
        grid-template-columns: 1fr;
    }
    
    .contact-container {
        grid-template-columns: 1fr;
    }
    
    .form-group {
        grid-template-columns: 1fr;
    }
    
    .topic {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .mark-btn {
        margin: 1rem 0 0 0;
        width: 100%;
    }
    
    main {
        padding: 0 1rem;
    }
    
    .footer-content {
        grid-template-columns: 1fr;
        text-align: center;
    }
    
    .subjects-section, .features-section, .testimonials-section, .contact-section {
        margin: 2rem 0;
        padding: 2rem 0;
    }
}

@media (max-width: 900px) {
    .nav-container {
        flex-direction: row;
        justify-content: space-between;
        align-items: center;
    }
    .nav-logo {
        order: 1;
        margin-left: 0;
    }
    .hamburger {
        order: 3;
        margin-left: auto;
    }
    .mobile-menu {
        order: 2;
    }
}

html {
    scroll-behavior: smooth;
}

/* --- Professional Loader --- */
.loader-content-pro {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: rgba(255,255,255,0.7);
    border-radius: 24px;
    box-shadow: 0 8px 32px rgba(44,62,80,0.10);
    padding: 3rem 4rem 2.5rem 4rem;
    min-width: 320px;
    min-height: 220px;
    animation: fadeInUp 0.7s;
}
.loader-logo {
    display: flex;
    align-items: center;
    gap: 0.7rem;
    font-size: 2rem;
    font-weight: 700;
    color: #2d3e50;
    margin-bottom: 2.2rem;
    letter-spacing: 2px;
}
.loader-logo i {
    color: #4f8cff;
    font-size: 2.2rem;
    animation: float 2.5s ease-in-out infinite;
}
.loader-spinner-pro {
    width: 48px;
    height: 48px;
    border: 5px solid #e3eafd;
    border-top: 5px solid #4f8cff;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: 1.5rem;
}
@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}
.loader-text {
    font-size: 1.15rem;
    color: #3461a4;
    font-weight: 500;
    letter-spacing: 1px;
    margin-top: 0.5rem;
    display: flex;
    align-items: center;
    justify-content: center;
}
.loader-dot {
    animation: loader-dot-blink 1.2s infinite;
    font-size: 1.3rem;
    color: #4f8cff;
}
.loader-dot:nth-child(2) { animation-delay: 0.2s; }
.loader-dot:nth-child(3) { animation-delay: 0.4s; }
@keyframes loader-dot-blink {
    0%, 80%, 100% { opacity: 0.2; }
    40% { opacity: 1; }
}

/* --- Dark Mode Toggle Button --- */
#dark-mode-toggle {
    flex: 0 0 auto;
    background: none;
    border: none;
    outline: none;
    cursor: pointer;
    margin-left: 2rem;
    z-index: 2;
}
#dark-mode-toggle .dark-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    transition: transform 0.4s cubic-bezier(.4,2,.6,1), color 0.3s;
}
#dark-mode-toggle .fa-moon {
    transition: transform 0.4s cubic-bezier(.4,2,.6,1), color 0.3s;
}
#dark-mode-toggle .fa-sun {
    color: #ffd700;
    transition: transform 0.4s cubic-bezier(.4,2,.6,1), color 0.3s;
}
#dark-mode-toggle:active .dark-icon {
    transform: scale(0.9) rotate(-20deg);
}

/* --- Dark Mode Styles --- */
body.dark-mode {
    background: #181c24;
    color: #e3eafd;
}
body.dark-mode .navbar,
body.dark-mode .nav-container {
    background: rgba(24,28,36,0.98) !important;
    box-shadow: 0 8px 32px rgba(0,0,0,0.25);
    border: 1px solid rgba(44,62,80,0.3);
}
body.dark-mode .nav-logo,
body.dark-mode .nav-links li a {
    color: #e3eafd;
}
body.dark-mode .nav-links li a:hover {
    color: #ffd700;
    background: rgba(255,215,0,0.08);
}
body.dark-mode #dark-mode-toggle {
    color: #ffd700;
}
body.dark-mode .parallax-hero {
    background-image: url('https://images.unsplash.com/photo-1465101046530-73398c7f28ca?auto=format&fit=crop&w=1200&q=80');
}
body.dark-mode .parallax-hero::before {
    background: linear-gradient(135deg, rgba(24,28,36,0.92), rgba(44,62,80,0.7));
}
body.dark-mode .hero-content,
body.dark-mode .hero-content h1,
body.dark-mode .hero-content p {
    color: #e3eafd;
}
body.dark-mode .hero-badge {
    background: rgba(44,62,80,0.3);
    color: #ffd700;
    border: 1px solid rgba(255,215,0,0.2);
}
body.dark-mode .gradient-text {
    background: linear-gradient(135deg, #ffd700, #4f8cff);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
body.dark-mode .cta-btn.primary {
    background: linear-gradient(135deg, #ffd700, #4f8cff);
    color: #181c24;
}
body.dark-mode .cta-btn.secondary {
    background: rgba(255,255,255,0.08);
    color: #ffd700;
    border: 2px solid #ffd700;
}
body.dark-mode .cta-btn.primary:hover {
    box-shadow: 0 12px 35px rgba(255,215,0,0.2);
}
body.dark-mode .cta-btn.secondary:hover {
    background: rgba(255,255,255,0.15);
}
body.dark-mode .subjects-section,
body.dark-mode .features-section,
body.dark-mode .stats-section,
body.dark-mode .testimonials-section,
body.dark-mode .contact-section,
body.dark-mode .revision-section {
    background: rgba(24,28,36,0.92) !important;
    color: #e3eafd;
    box-shadow: 0 8px 32px rgba(0,0,0,0.25);
}
body.dark-mode .section-header h2,
body.dark-mode .section-header p {
    color: #ffd700;
}
body.dark-mode .subject-btn {
    background: linear-gradient(135deg, #232a36, #2d3e50);
    color: #ffd700;
    box-shadow: 0 8px 25px rgba(44,62,80,0.18);
}
body.dark-mode .subject-btn:hover {
    background: linear-gradient(135deg, #ffd700, #4f8cff);
    color: #181c24;
}
body.dark-mode .feature-card,
body.dark-mode .stat-card,
body.dark-mode .testimonial,
body.dark-mode .contact-item {
    background: rgba(36,40,50,0.98) !important;
    color: #e3eafd;
    border: 1px solid rgba(44,62,80,0.3);
}
body.dark-mode .feature-icon,
body.dark-mode .stat-icon,
body.dark-mode .contact-item i {
    background: linear-gradient(135deg, #ffd700, #4f8cff);
    color: #181c24;
}
body.dark-mode .feature-card h3,
body.dark-mode .stat-content h3,
body.dark-mode .author-name {
    color: #ffd700;
}
body.dark-mode .feature-card p,
body.dark-mode .stat-content p,
body.dark-mode .author-title,
body.dark-mode .testimonial p,
body.dark-mode .testimonial span,
body.dark-mode .contact-item p {
    color: #e3eafd;
}
body.dark-mode .mark-btn {
    background: linear-gradient(135deg, #ffd700, #4f8cff);
    color: #181c24;
}
body.dark-mode .mark-btn:disabled {
    background: #b2b2b2;
    color: #888;
}
body.dark-mode #progress {
    color: #ffd700;
}
body.dark-mode #back-btn {
    background: linear-gradient(135deg, #4f8cff, #ffd700);
    color: #181c24;
}
body.dark-mode .loader-content-pro {
    background: rgba(24,28,36,0.95);
    color: #ffd700;
}
body.dark-mode .loader-logo {
    color: #ffd700;
}
body.dark-mode .loader-logo i {
    color: #ffd700;
}
body.dark-mode .loader-spinner-pro {
    border: 5px solid #232a36;
    border-top: 5px solid #ffd700;
}
body.dark-mode .loader-text {
    color: #ffd700;
}
body.dark-mode .loader-dot {
    color: #ffd700;
}
body.dark-mode footer {
    background: #181c24;
    color: #ffd700;
}
body.dark-mode .footer-logo,
body.dark-mode .footer-section h4 {
    color: #ffd700;
}
body.dark-mode .footer-section p,
body.dark-mode .footer-section ul li a,
body.dark-mode .footer-bottom {
    color: #e3eafd;
}
body.dark-mode .footer-section ul li a:hover {
    color: #ffd700;
}
body.dark-mode .social-links a {
    background: rgba(255,215,0,0.08);
    color: #ffd700;
}
body.dark-mode .social-links a:hover {
    background: #ffd700;
    color: #181c24;
}

.dark-mode .nav-container {
    border: none;
    box-shadow: none;
}

.dark-mode .navbar {
    box-shadow: none;
    border: none;
}

/* Modern Hamburger Animation */
.hamburger {
    display: none;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    width: 48px;
    height: 48px;
    background: none;
    border: none;
    cursor: pointer;
    z-index: 1201;
    margin-left: 1rem;
    border-radius: 50%;
    box-shadow: 0 2px 8px rgba(44,62,80,0.07);
    transition: background 0.2s;
    position: relative;
}
.hamburger:active, .hamburger:hover {
    background: rgba(79,140,255,0.08);
}
.hamburger span {
    display: block;
    width: 28px;
    height: 3.5px;
    margin: 5px 0;
    background: #2d3e50;
    border-radius: 2.5px;
    transition: all 0.35s cubic-bezier(.77,0,.18,1);
    position: relative;
}
.hamburger.open span:nth-child(1) {
    transform: translateY(8.5px) rotate(45deg);
}
.hamburger.open span:nth-child(2) {
    opacity: 0;
    transform: scaleX(0.5);
}
.hamburger.open span:nth-child(3) {
    transform: translateY(-8.5px) rotate(-45deg);
}
body.dark-mode .hamburger span {
    background: #f3f6fa;
}

/* Mobile menu overlay blur/fade */
.mobile-menu::before {
    content: '';
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(44,62,80,0.18);
    backdrop-filter: blur(2.5px);
    z-index: -1;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.35s cubic-bezier(.77,0,.18,1);
}
.mobile-menu.open::before {
    opacity: 1;
    pointer-events: auto;
}

/* Mobile menu overlay */
.mobile-menu {
    position: fixed;
    top: 0;
    right: -100vw;
    width: 80vw;
    max-width: 340px;
    height: 100vh;
    background: rgba(255,255,255,0.97);
    box-shadow: -4px 0 32px rgba(0,0,0,0.15);
    z-index: 1200;
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    padding: 2.5rem 1.5rem 1.5rem 1.5rem;
    transition: right 0.35s cubic-bezier(.77,0,.18,1);
    opacity: 0;
    pointer-events: none;
}
.mobile-menu.open {
    right: 0;
    opacity: 1;
    pointer-events: auto;
}
.mobile-menu ul {
    list-style: none;
    padding: 0;
    margin: 0 0 2rem 0;
    width: 100%;
}
.mobile-menu ul li {
    margin-bottom: 1.2rem;
}
.mobile-menu ul li a {
    color: #2d3e50;
    font-size: 1.15rem;
    font-weight: 600;
    text-decoration: none;
    display: block;
    padding: 0.5rem 0;
    border-radius: 8px;
    transition: background 0.2s, color 0.2s;
}
.mobile-menu ul li a:hover {
    background: rgba(79,140,255,0.08);
    color: #4f8cff;
}
#mobile-dark-mode-toggle {
    background: none;
    border: none;
    font-size: 1.5rem;
    color: #2d3e50;
    margin-top: 1.5rem;
    cursor: pointer;
    align-self: flex-start;
    transition: color 0.2s;
}
#mobile-dark-mode-toggle .dark-icon {
    font-size: 1.5rem;
}

@media (max-width: 900px) {
    .nav-links, #dark-mode-toggle {
        display: none !important;
    }
    .hamburger {
        display: flex;
    }
    .nav-container {
        justify-content: space-between;
    }
}

@media (max-width: 900px) {
    .mobile-menu {
        display: flex;
    }
}

body.dark-mode .mobile-menu {
    background: rgba(24,28,36,0.98);
}
body.dark-mode .mobile-menu ul li a {
    color: #f3f6fa;
}
body.dark-mode .mobile-menu ul li a:hover {
    background: rgba(79,140,255,0.10);
    color: #4f8cff;
}
body.dark-mode #mobile-dark-mode-toggle {
    color: #f3f6fa;
}