/* MathPrime Website - Minimalist Light Theme for Teenagers */
@import url('https://fonts.googleapis.com/css2?family=Be Vietnam Pro:wght@300;400;500;600;700;800&display=swap');

:root {
    --bg-color: #FAFAFC;
    --card-bg: #FFFFFF;
    --card-border: #E2E8F0;
    --primary-color: #0F172A;
    --accent-color: #4F46E5; /* Royal Indigo */
    --accent-hover: #4338CA;
    --text-primary: #1E293B;
    --text-secondary: #64748B;
    --gradient-primary: linear-gradient(135deg, #0EA5E9 0%, #6366F1 100%); /* Bright Sky Blue to Indigo */
    --gradient-glow: 0 10px 25px rgba(99, 102, 241, 0.12);
    --font-main: 'Be Vietnam Pro', sans-serif;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --shadow-soft: 0 10px 30px -5px rgba(15, 23, 42, 0.05), 0 5px 15px -5px rgba(15, 23, 42, 0.03);
    --shadow-hover: 0 20px 40px -10px rgba(99, 102, 241, 0.12), 0 5px 15px -5px rgba(15, 23, 42, 0.05);
}

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

body {
    background-color: var(--bg-color);
    color: var(--text-primary);
    font-family: var(--font-main);
    line-height: 1.6;
    overflow-x: hidden;
    background-image: 
        radial-gradient(circle at 10% 20%, rgba(14, 165, 233, 0.03) 0%, transparent 40%),
        radial-gradient(circle at 90% 80%, rgba(99, 102, 241, 0.03) 0%, transparent 45%);
    background-attachment: fixed;
}

/* Custom Scrollbar */
::-webkit-scrollbar {
    width: 8px;
}
::-webkit-scrollbar-track {
    background: var(--bg-color);
}
::-webkit-scrollbar-thumb {
    background: rgba(99, 102, 241, 0.2);
    border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
    background: var(--accent-color);
}

/* Typography & Layout Utilities */
h1, h2, h3, h4 {
    font-weight: 700;
    letter-spacing: -0.02em;
}

h2 {
    font-size: 2.3rem;
    margin-bottom: 1rem;
    text-align: center;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

p {
    color: var(--text-secondary);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

section {
    padding: 80px 0;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 28px;
    font-family: var(--font-main);
    font-size: 1rem;
    font-weight: 600;
    border-radius: 16px; /* Slightly rounded, modern but not overly rounded pill */
    text-decoration: none;
    cursor: pointer;
    transition: var(--transition);
    border: none;
}

.btn-primary {
    background: var(--gradient-primary);
    color: #FFFFFF;
    box-shadow: var(--gradient-glow);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 15px 30px rgba(99, 102, 241, 0.25);
}

.btn-secondary {
    background: #FFFFFF;
    color: var(--text-primary);
    border: 1px solid var(--card-border);
    box-shadow: 0 2px 4px rgba(0,0,0,0.02);
}

.btn-secondary:hover {
    background: #F8FAFC;
    border-color: var(--accent-color);
    transform: translateY(-2px);
}

/* Header */
header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 1000;
    background: rgba(250, 250, 252, 0.8);
    backdrop-filter: blur(16px);
    border-bottom: 1px solid var(--card-border);
    transition: var(--transition);
}

header.scrolled {
    padding: 8px 0;
    background: rgba(255, 255, 255, 0.95);
    box-shadow: 0 4px 20px rgba(15, 23, 42, 0.03);
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 80px;
}

.logo {
    font-size: 1.6rem;
    font-weight: 800;
    color: var(--primary-color);
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 8px;
}

.logo span {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.logo i {
    color: #0EA5E9;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 32px;
    align-items: center;
}

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 600;
    transition: var(--transition);
}

.nav-link:hover, .nav-link.active {
    color: var(--accent-color);
}

.menu-toggle {
    display: none;
    background: none;
    border: none;
    color: var(--text-primary);
    font-size: 1.5rem;
    cursor: pointer;
}

/* Hero Section */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding-top: 100px;
    position: relative;
}

.hero-grid {
    display: grid;
    grid-template-columns: 1.2fr 0.8fr;
    gap: 48px;
    align-items: center;
}

.hero-content h1 {
    font-size: 3.4rem;
    line-height: 1.2;
    margin-bottom: 20px;
    color: var(--primary-color);
}

.hero-content h1 span {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.hero-content p {
    font-size: 1.15rem;
    margin-bottom: 32px;
    max-width: 600px;
    color: var(--text-secondary);
}

.hero-btns {
    display: flex;
    gap: 16px;
    margin-bottom: 40px;
}

.hero-stats {
    display: flex;
    gap: 40px;
}

.stat-item h3 {
    font-size: 2.2rem;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: 4px;
}

.stat-item p {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.hero-visual {
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
}

.hero-img-wrapper {
    position: relative;
    border-radius: 24px;
    overflow: hidden;
    border: 1px solid var(--card-border);
    box-shadow: var(--shadow-soft);
    transition: var(--transition);
    width: 100%;
}

.hero-img-wrapper:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-hover);
}

.hero-image {
    width: 100%;
    height: 380px;
    object-fit: cover;
    display: block;
}

/* Glassmorphism Badge on Hero Visual */
.hero-badge {
    position: absolute;
    bottom: 24px;
    left: -20px;
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(12px);
    border: 1px solid rgba(255,255,255,0.6);
    padding: 16px 24px;
    border-radius: 20px;
    display: flex;
    align-items: center;
    gap: 12px;
    z-index: 2;
    box-shadow: 0 10px 30px rgba(15, 23, 42, 0.08);
    animation: float 4s ease-in-out infinite;
}

.hero-badge-icon {
    width: 48px;
    height: 48px;
    background: rgba(14, 165, 233, 0.1);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #0EA5E9;
    font-size: 1.2rem;
}

.hero-badge-text h4 {
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--text-primary);
}

.hero-badge-text p {
    font-size: 0.8rem;
    color: var(--text-secondary);
}

/* About / Teacher Section */
.about {
    background: #FFFFFF;
    border-top: 1px solid var(--card-border);
    border-bottom: 1px solid var(--card-border);
}

.about-grid {
    display: grid;
    grid-template-columns: 0.8fr 1.2fr;
    gap: 64px;
    align-items: center;
}

.about-img-wrapper {
    position: relative;
    border-radius: 24px;
    overflow: hidden;
    border: 1px solid var(--card-border);
    box-shadow: var(--shadow-soft);
}

.about-img {
    width: 100%;
    height: auto;
    display: block;
    object-fit: cover;
}

.about-content h2 {
    text-align: left;
}

.about-tag {
    color: var(--accent-color);
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    font-size: 0.85rem;
    margin-bottom: 8px;
    display: block;
}

.about-intro {
    font-size: 1.15rem;
    color: var(--text-primary);
    margin-bottom: 20px;
    font-weight: 500;
}

.about-details {
    margin-bottom: 28px;
}

.about-details p {
    margin-bottom: 16px;
    font-size: 1rem;
    font-style: italic;
}

.teacher-features {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
}

.feature-box {
    background: var(--bg-color);
    border: 1px solid var(--card-border);
    padding: 20px;
    border-radius: 20px;
    transition: var(--transition);
}

.feature-box:hover {
    border-color: var(--accent-color);
    transform: translateY(-3px);
    box-shadow: var(--shadow-soft);
}

.feature-box i {
    color: #6366F1;
    font-size: 1.5rem;
    margin-bottom: 12px;
    display: block;
}

.feature-box h4 {
    font-size: 1.05rem;
    margin-bottom: 6px;
    color: var(--text-primary);
}

.feature-box p {
    font-size: 0.85rem;
    color: var(--text-secondary);
}

/* Courses Section */
.courses-filter {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin-bottom: 40px;
    flex-wrap: wrap;
}

.filter-btn {
    background: #FFFFFF;
    color: var(--text-secondary);
    border: 1px solid var(--card-border);
    padding: 10px 22px;
    border-radius: 14px;
    cursor: pointer;
    font-family: var(--font-main);
    font-weight: 600;
    transition: var(--transition);
    font-size: 0.9rem;
}

.filter-btn.active, .filter-btn:hover {
    background: var(--accent-color);
    color: #FFFFFF;
    border-color: var(--accent-color);
    box-shadow: 0 4px 12px rgba(99, 102, 241, 0.2);
}

.courses-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 32px;
}

.course-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 24px;
    overflow: hidden;
    display: flex;
    flex-direction: column;
    height: 100%;
    box-shadow: var(--shadow-soft);
    transition: var(--transition);
}

.course-card:hover {
    transform: translateY(-8px);
    border-color: var(--accent-color);
    box-shadow: var(--shadow-hover);
}

.course-image-wrapper {
    position: relative;
    height: 200px;
    overflow: hidden;
}

.course-img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: var(--transition);
}

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

.course-tag {
    position: absolute;
    top: 16px;
    left: 16px;
    background: rgba(255, 255, 255, 0.95);
    color: var(--accent-color);
    border: 1px solid rgba(99, 102, 241, 0.2);
    padding: 6px 14px;
    border-radius: 12px;
    font-size: 0.8rem;
    font-weight: 700;
    backdrop-filter: blur(8px);
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}

.course-info {
    padding: 24px;
    display: flex;
    flex-direction: column;
    flex-grow: 1;
}

.course-title {
    font-size: 1.25rem;
    margin-bottom: 10px;
    line-height: 1.35;
    color: var(--text-primary);
}

.course-desc {
    font-size: 0.9rem;
    margin-bottom: 20px;
    color: var(--text-secondary);
    flex-grow: 1;
}

.course-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-top: 1px solid var(--card-border);
    padding-top: 16px;
    margin-bottom: 20px;
}

.meta-item {
    display: flex;
    align-items: center;
    gap: 6px;
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.meta-item i {
    color: #0EA5E9;
}

.course-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.course-price {
    font-size: 1.35rem;
    font-weight: 800;
    color: var(--text-primary);
}

.course-price span {
    font-size: 0.85rem;
    color: var(--text-secondary);
    font-weight: 400;
}

/* Video Section */
.video-section {
    background: #FFFFFF;
    border-top: 1px solid var(--card-border);
    border-bottom: 1px solid var(--card-border);
}

.video-container {
    max-width: 800px;
    margin: 0 auto;
    position: relative;
    border-radius: 24px;
    overflow: hidden;
    border: 1px solid var(--card-border);
    box-shadow: var(--shadow-soft);
}

.video-aspect-ratio {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 aspect ratio */
    height: 0;
}

.video-aspect-ratio iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: 0;
}

/* Resources & Blog Section */
.resources-search {
    max-width: 500px;
    margin: 0 auto 40px auto;
    position: relative;
}

.search-input {
    width: 100%;
    padding: 14px 20px;
    padding-right: 50px;
    border-radius: 16px;
    background: #FFFFFF;
    border: 1px solid var(--card-border);
    color: var(--text-primary);
    font-family: var(--font-main);
    font-size: 0.95rem;
    transition: var(--transition);
    box-shadow: 0 2px 8px rgba(0,0,0,0.01);
}

.search-input:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 12px rgba(99, 102, 241, 0.1);
}

.search-icon {
    position: absolute;
    right: 20px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-secondary);
    font-size: 1.1rem;
    pointer-events: none;
}

.resources-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(350px, 1fr));
    gap: 32px;
}

.resource-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 24px;
    padding: 24px;
    display: flex;
    flex-direction: column;
    height: 100%;
    box-shadow: var(--shadow-soft);
    transition: var(--transition);
}

.resource-card:hover {
    transform: translateY(-5px);
    border-color: var(--accent-color);
    box-shadow: var(--shadow-hover);
}

.resource-type {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    color: #6366F1;
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    margin-bottom: 12px;
}

.resource-title {
    font-size: 1.15rem;
    margin-bottom: 10px;
    line-height: 1.35;
    color: var(--text-primary);
}

.resource-excerpt {
    font-size: 0.9rem;
    margin-bottom: 20px;
    color: var(--text-secondary);
    flex-grow: 1;
}

.resource-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-top: 1px solid var(--card-border);
    padding-top: 16px;
}

.resource-date {
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.resource-download-btn {
    color: var(--accent-color);
    text-decoration: none;
    font-weight: 700;
    font-size: 0.85rem;
    display: flex;
    align-items: center;
    gap: 6px;
    transition: var(--transition);
}

.resource-download-btn:hover {
    color: var(--accent-hover);
    transform: translateX(4px);
}

/* Contact / Register Form */
.contact {
    background: #FFFFFF;
    border-top: 1px solid var(--card-border);
}

.contact-grid {
    display: grid;
    grid-template-columns: 0.9fr 1.1fr;
    gap: 64px;
    align-items: center;
}

.contact-info-panel h2 {
    text-align: left;
}

.contact-info-panel p {
    margin-bottom: 32px;
    font-size: 1.05rem;
}

.contact-details {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.contact-item {
    display: flex;
    align-items: center;
    gap: 16px;
}

.contact-icon {
    width: 44px;
    height: 44px;
    background: rgba(99, 102, 241, 0.08);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--accent-color);
    font-size: 1.1rem;
}

.contact-text h4 {
    font-size: 1rem;
    margin-bottom: 2px;
    color: var(--text-primary);
}

.contact-text p {
    margin: 0;
    font-size: 0.85rem;
}

.contact-form-panel {
    background: var(--bg-color);
    border: 1px solid var(--card-border);
    padding: 36px;
    border-radius: 24px;
    box-shadow: 0 4px 20px rgba(0,0,0,0.01);
}

.contact-form-panel h3 {
    font-size: 1.5rem;
    margin-bottom: 20px;
    color: var(--text-primary);
}

.form-group {
    margin-bottom: 16px;
}

.form-label {
    display: block;
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 6px;
    color: var(--text-primary);
}

.form-control {
    width: 100%;
    padding: 12px 16px;
    border-radius: 12px;
    background: #FFFFFF;
    border: 1px solid var(--card-border);
    color: var(--text-primary);
    font-family: var(--font-main);
    font-size: 0.9rem;
    transition: var(--transition);
}

.form-control:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 10px rgba(99, 102, 241, 0.08);
}

textarea.form-control {
    resize: none;
    height: 100px;
}

/* Modal Popup (for Details / Checkout) */
.modal {
    position: fixed;
    inset: 0;
    background: rgba(15, 23, 42, 0.4);
    backdrop-filter: blur(8px);
    z-index: 2000;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    pointer-events: none;
    transition: var(--transition);
    padding: 24px;
}

.modal.active {
    opacity: 1;
    pointer-events: all;
}

.modal-content {
    background: #FFFFFF;
    border: 1px solid var(--card-border);
    width: 100%;
    max-width: 550px;
    border-radius: 24px;
    padding: 32px;
    position: relative;
    transform: scale(0.95);
    transition: var(--transition);
    box-shadow: 0 30px 60px -15px rgba(15, 23, 42, 0.15);
}

.modal.active .modal-content {
    transform: scale(1);
}

.modal-close {
    position: absolute;
    top: 20px;
    right: 20px;
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 1.3rem;
    cursor: pointer;
    transition: var(--transition);
}

.modal-close:hover {
    color: var(--accent-color);
}

.modal-title {
    font-size: 1.5rem;
    margin-bottom: 12px;
    color: var(--text-primary);
}

.checkout-details {
    margin-top: 20px;
    padding-top: 20px;
    border-top: 1px solid var(--card-border);
}

.qr-code-wrapper {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
    margin: 20px 0;
    padding: 16px;
    background: #F8FAFC;
    border: 1px solid var(--card-border);
    border-radius: 16px;
    width: fit-content;
    margin-left: auto;
    margin-right: auto;
}

.qr-code-wrapper img {
    max-width: 180px;
}

.qr-code-wrapper p {
    color: var(--text-primary);
    font-weight: 700;
    margin: 0;
    font-size: 0.9rem;
}

.bank-info {
    background: var(--bg-color);
    border: 1px solid var(--card-border);
    padding: 16px;
    border-radius: 12px;
    margin-bottom: 20px;
}

.bank-info-row {
    display: flex;
    justify-content: space-between;
    margin-bottom: 8px;
    font-size: 0.9rem;
}

.bank-info-row:last-child {
    margin-bottom: 0;
}

.bank-label {
    color: var(--text-secondary);
}

.bank-value {
    font-weight: 600;
    color: var(--text-primary);
}

/* Footer */
footer {
    background: #FFFFFF;
    padding: 60px 0 30px 0;
    border-top: 1px solid var(--card-border);
}

.footer-grid {
    display: grid;
    grid-template-columns: 1.5fr 1fr 1fr;
    gap: 48px;
    margin-bottom: 40px;
}

.footer-brand p {
    margin-top: 16px;
    max-width: 320px;
    font-size: 0.9rem;
}

.footer-links h4, .footer-contact h4 {
    font-size: 1rem;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.footer-links ul {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.footer-links a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: var(--transition);
    font-size: 0.9rem;
    font-weight: 500;
}

.footer-links a:hover {
    color: var(--accent-color);
}

.social-links {
    display: flex;
    gap: 12px;
    margin-top: 16px;
}

.social-btn {
    width: 36px;
    height: 36px;
    border-radius: 10px;
    background: var(--bg-color);
    border: 1px solid var(--card-border);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-secondary);
    text-decoration: none;
    transition: var(--transition);
}

.social-btn:hover {
    background: var(--accent-color);
    color: #FFFFFF;
    border-color: var(--accent-color);
    transform: translateY(-3px);
}

.copyright {
    text-align: center;
    font-size: 0.8rem;
    color: var(--text-secondary);
    border-top: 1px solid var(--card-border);
    padding-top: 24px;
}

/* ---------------------------------------------------- */
/* NEW STYLES: COURSE DETAILS PAGE LAYOUT & ACCORDIONS */
/* ---------------------------------------------------- */

.course-detail-layout {
    display: grid;
    grid-template-columns: 1.4fr 0.6fr;
    gap: 48px;
    align-items: start;
    padding-top: 120px;
}

.course-detail-main {
    display: flex;
    flex-direction: column;
    gap: 40px;
}

.course-intro-box h1 {
    font-size: 2.5rem;
    line-height: 1.25;
    margin-bottom: 16px;
    color: var(--primary-color);
}

.course-intro-box .course-tag {
    position: static;
    display: inline-block;
    margin-bottom: 16px;
}

.course-intro-box .course-desc-large {
    font-size: 1.1rem;
    line-height: 1.6;
    margin-bottom: 24px;
    color: var(--text-secondary);
}

.course-target-audience {
    background: #FFFFFF;
    border: 1px solid var(--card-border);
    border-radius: 20px;
    padding: 24px;
    box-shadow: var(--shadow-soft);
}

.course-target-audience h3 {
    font-size: 1.25rem;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.course-target-audience ul {
    list-style: none;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
}

.course-target-audience li {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 0.95rem;
    color: var(--text-secondary);
}

.course-target-audience li i {
    color: #10B981;
}

.course-detail-sidebar {
    position: sticky;
    top: 100px;
    background: #FFFFFF;
    border: 1px solid var(--card-border);
    border-radius: 24px;
    padding: 32px;
    box-shadow: var(--shadow-soft);
}

.sidebar-img-placeholder {
    width: 100%;
    height: 180px;
    background: #F1F5F9;
    border-radius: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
    position: relative;
    border: 1px solid var(--card-border);
}

.sidebar-img-placeholder img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    display: block;
}

.sidebar-price {
    font-size: 2rem;
    font-weight: 800;
    margin: 24px 0 16px 0;
    color: var(--text-primary);
}

.sidebar-price span {
    font-size: 1rem;
    color: var(--text-secondary);
    font-weight: 400;
}

.sidebar-features {
    list-style: none;
    margin: 24px 0;
    display: flex;
    flex-direction: column;
    gap: 12px;
    border-top: 1px solid var(--card-border);
    padding-top: 20px;
}

.sidebar-features li {
    display: flex;
    align-items: center;
    gap: 12px;
    font-size: 0.95rem;
    color: var(--text-secondary);
}

.sidebar-features i {
    color: #6366F1;
    font-size: 1.1rem;
}

/* Accordion Syllabus Styling */
.syllabus-section h3 {
    font-size: 1.6rem;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.syllabus-accordion {
    display: flex;
    flex-direction: column;
    gap: 16px;
    margin-top: 24px;
}

.accordion-item {
    background: #FFFFFF;
    border: 1px solid var(--card-border);
    border-radius: 16px;
    overflow: hidden;
    box-shadow: 0 2px 8px rgba(0,0,0,0.01);
    transition: var(--transition);
}

.accordion-header {
    padding: 20px 24px;
    background: #FFFFFF;
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    font-weight: 700;
    font-size: 1.05rem;
    color: var(--text-primary);
    user-select: none;
    transition: var(--transition);
}

.accordion-header:hover {
    background: #F8FAFC;
}

.accordion-header i.chevron-icon {
    transition: var(--transition);
    color: var(--text-secondary);
}

.accordion-item.active {
    border-color: var(--accent-color);
}

.accordion-item.active .accordion-header i.chevron-icon {
    transform: rotate(180deg);
    color: var(--accent-color);
}

.accordion-item.active .accordion-header {
    border-bottom: 1px solid var(--card-border);
    background: #F8FAFC;
}

.accordion-content {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease-out;
    background: #FAFAFC;
}

.lesson-list {
    list-style: none;
    padding: 8px 0;
}

.lesson-item {
    display: block;
    padding: 0;
    border-bottom: 1px solid rgba(15, 23, 42, 0.03);
    font-size: 0.95rem;
    color: var(--text-secondary);
}

.lesson-item:last-child {
    border-bottom: none;
}

.lesson-left {
    display: flex;
    align-items: center;
    gap: 12px;
}

.lesson-left i {
    font-size: 1.1rem;
    width: 20px;
    text-align: center;
}

.lesson-left i.fa-circle-play {
    color: #0EA5E9;
}

.lesson-left i.fa-file-pdf {
    color: #EF4444;
}

.lesson-left i.fa-lock {
    color: #94A3B8;
}

.lesson-right {
    display: flex;
    align-items: center;
    gap: 12px;
}

.lesson-btn {
    text-decoration: none;
    color: var(--accent-color);
    font-weight: 700;
    font-size: 0.8rem;
    display: flex;
    align-items: center;
    gap: 4px;
    padding: 4px 10px;
    border-radius: 8px;
    background: rgba(99, 102, 241, 0.06);
    transition: var(--transition);
}

.lesson-btn:hover {
    background: var(--accent-color);
    color: #FFFFFF;
}

.lesson-duration {
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.lesson-locked {
    color: #94A3B8;
    font-size: 0.85rem;
}

/* Animations */
@keyframes float {
    0% { transform: translateY(0px); }
    50% { transform: translateY(-8px); }
    100% { transform: translateY(0px); }
}

/* Responsive Media Queries */
@media (max-width: 992px) {
    h2 { font-size: 1.85rem; }
    .hero-grid {
        grid-template-columns: 1fr;
        gap: 48px;
        text-align: center;
    }
    .hero-content h1 { font-size: 2.8rem; }
    .hero-content p { margin-left: auto; margin-right: auto; }
    .hero-btns { justify-content: center; }
    .hero-stats { justify-content: center; }
    .hero-badge { left: 24px; bottom: -20px; }
    .about-grid { grid-template-columns: 1fr; gap: 40px; }
    .about-content h2 { text-align: center; }
    .contact-grid { grid-template-columns: 1fr; gap: 40px; }
    .course-detail-layout {
        grid-template-columns: 1fr;
        gap: 40px;
    }
    .course-detail-sidebar {
        position: static;
    }
    .course-target-audience ul {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .nav-menu {
        position: fixed;
        top: 80px;
        left: -100%;
        width: 100%;
        height: calc(100vh - 80px);
        background: rgba(255, 255, 255, 0.98);
        backdrop-filter: blur(20px);
        flex-direction: column;
        justify-content: center;
        gap: 32px;
        transition: var(--transition);
        box-shadow: 0 10px 30px rgba(15, 23, 42, 0.05);
    }
    .nav-menu.active {
        left: 0;
    }
    .menu-toggle {
        display: block;
    }
    .footer-grid {
        grid-template-columns: 1fr;
        gap: 28px;
    }
}

/* Admin Inline Editor Styles */
.admin-toolbar {
    background: #0F172A;
    color: #FFFFFF;
    padding: 12px 24px;
    position: sticky;
    top: 0;
    z-index: 1900;
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 2px solid var(--accent-color);
    box-shadow: 0 4px 12px rgba(15,23,42,0.15);
    font-family: var(--font-main);
    font-size: 0.9rem;
}

.admin-toolbar-left {
    display: flex;
    align-items: center;
    gap: 8px;
    font-weight: 700;
}

.admin-toolbar-left i {
    color: #FBBF24;
}

.admin-toolbar-right {
    display: flex;
    align-items: center;
    gap: 16px;
}

.admin-toggle-wrapper {
    display: flex;
    align-items: center;
    gap: 8px;
}

.admin-toggle-switch {
    position: relative;
    display: inline-block;
    width: 44px;
    height: 22px;
}

.admin-toggle-switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.admin-toggle-slider {
    position: absolute;
    cursor: pointer;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: #475569;
    transition: .3s;
    border-radius: 22px;
}

.admin-toggle-slider:before {
    position: absolute;
    content: "";
    height: 16px;
    width: 16px;
    left: 3px;
    bottom: 3px;
    background-color: white;
    transition: .3s;
    border-radius: 50%;
}

.admin-toggle-switch input:checked + .admin-toggle-slider {
    background-color: var(--accent-color);
}

.admin-toggle-switch input:checked + .admin-toggle-slider:before {
    transform: translateX(22px);
}

.gear-btn {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text-secondary);
    margin-left: 8px;
    transition: var(--transition);
    display: none; /* Bị ẩn theo mặc định, hiện khi bật chế độ sửa */
    width: 28px;
    height: 28px;
    border-radius: 50%;
    align-items: center;
    justify-content: center;
}

.gear-btn:hover {
    color: var(--accent-color);
    background: #F1F5F9;
}

/* Hộp công cụ inline cho chương học */
.inline-action-bar {
    background: #F8FAFC;
    border: 1px dashed var(--accent-color);
    border-radius: 12px;
    padding: 12px 16px;
    margin: 12px 24px;
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    align-items: center;
    box-shadow: inset 0 2px 4px rgba(0,0,0,0.02);
}

.inline-action-btn {
    background: #FFFFFF;
    color: var(--text-primary);
    border: 1px solid var(--card-border);
    border-radius: 8px;
    padding: 6px 12px;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    transition: var(--transition);
}

.inline-action-btn:hover {
    border-color: var(--accent-color);
    color: var(--accent-color);
    background: rgba(99, 102, 241, 0.05);
}

.inline-action-btn.delete-btn:hover {
    border-color: #EF4444;
    color: #EF4444;
    background: rgba(239, 68, 68, 0.05);
}

.inline-action-btn.sort-btn:hover {
    border-color: #F59E0B;
    color: #F59E0B;
    background: rgba(245, 158, 11, 0.05);
}

.inline-action-label {
    font-size: 0.8rem;
    font-weight: 700;
    color: var(--text-secondary);
    margin-right: 8px;
}

/* Đẩy Header và Layout xuống dưới khi hiện Admin Toolbar */
body.admin-toolbar-visible header {
    top: 48px !important;
}
body.admin-toolbar-visible .course-detail-layout {
    padding-top: 168px !important;
}

/* Nút xem với vai trò học sinh (màu đỏ) */
.btn-student-role {
    background: #B91C1C !important;
    color: #FFFFFF !important;
    border: none !important;
}
.btn-student-role:hover {
    background: #991B1B !important;
    box-shadow: 0 4px 12px rgba(185, 28, 28, 0.2) !important;
}

/* ========================================== */
/* LOGIN / REGISTER PAGE & USER DROPDOWN CSS */
/* ========================================== */

/* Dropdown Tài Khoản trên Header */
.user-profile-menu {
    position: relative;
    display: inline-block;
}

.profile-trigger {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 50px;
    cursor: pointer;
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--text-primary);
    transition: var(--transition);
}

.profile-trigger:hover {
    border-color: var(--accent-color);
    background: rgba(99, 102, 241, 0.05);
}

.profile-trigger i {
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.profile-trigger .user-avatar {
    width: 28px;
    height: 28px;
    background: var(--gradient-primary);
    color: white;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.9rem;
    font-weight: bold;
}

.profile-dropdown-menu {
    position: absolute;
    top: calc(100% + 8px);
    right: 0;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 12px;
    box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.1);
    min-width: 200px;
    z-index: 1010;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-10px);
    transition: all 0.2s ease-in-out;
}

.profile-dropdown-menu.active {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.profile-dropdown-header {
    padding: 12px 16px;
    border-bottom: 1px solid var(--card-border);
}

.profile-dropdown-header .user-name {
    font-weight: 600;
    color: var(--text-primary);
    font-size: 0.95rem;
    display: block;
}

.profile-dropdown-header .user-email {
    font-size: 0.8rem;
    color: var(--text-secondary);
    display: block;
    margin-top: 2px;
}

.profile-dropdown-list {
    list-style: none;
    padding: 6px;
}

.profile-dropdown-item a, 
.profile-dropdown-item button {
    display: flex;
    align-items: center;
    gap: 10px;
    width: 100%;
    padding: 10px 12px;
    font-size: 0.9rem;
    color: var(--text-primary);
    border: none;
    background: transparent;
    text-align: left;
    cursor: pointer;
    border-radius: 8px;
    transition: var(--transition);
}

.profile-dropdown-item a:hover, 
.profile-dropdown-item button:hover {
    background: rgba(99, 102, 241, 0.08);
    color: var(--accent-color);
}

.profile-dropdown-item.logout-btn a:hover, 
.profile-dropdown-item.logout-btn button:hover {
    background: rgba(239, 68, 68, 0.08);
    color: #EF4444;
}

/* Trang Đăng Nhập / Đăng Ký */
.login-body {
    background: linear-gradient(135deg, #EEF2F6 0%, #E3E8EE 100%);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 40px 20px;
}

.login-wrapper {
    width: 100%;
    max-width: 450px;
}

.login-logo-container {
    text-align: center;
    margin-bottom: 30px;
}

.login-logo-container .logo {
    font-size: 2rem;
    justify-content: center;
}

.login-card {
    background: rgba(255, 255, 255, 0.8);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid rgba(255, 255, 255, 0.5);
    border-radius: 20px;
    box-shadow: 0 10px 30px rgba(15, 23, 42, 0.05);
    padding: 40px;
}

.login-card-title {
    text-align: center;
    font-size: 1.6rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 24px;
}

.login-tabs {
    display: flex;
    background: rgba(15, 23, 42, 0.05);
    padding: 4px;
    border-radius: 12px;
    margin-bottom: 30px;
}

.login-tab-btn {
    flex: 1;
    border: none;
    background: transparent;
    padding: 10px 0;
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-secondary);
    cursor: pointer;
    border-radius: 8px;
    transition: var(--transition);
}

.login-tab-btn.active {
    background: white;
    color: var(--accent-color);
    box-shadow: 0 4px 12px rgba(15, 23, 42, 0.05);
}

.login-form-group {
    margin-bottom: 20px;
}

.login-form-group label {
    display: block;
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--text-primary);
    margin-bottom: 8px;
}

.login-input {
    width: 100%;
    padding: 12px 16px;
    border: 1px solid var(--card-border);
    border-radius: 10px;
    background: white;
    font-size: 0.95rem;
    color: var(--text-primary);
    transition: var(--transition);
}

.login-input:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.1);
}

.login-submit-btn {
    width: 100%;
    padding: 14px;
    border: none;
    border-radius: 10px;
    background: var(--gradient-primary);
    color: white;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    margin-top: 10px;
    box-shadow: 0 4px 15px rgba(99, 102, 241, 0.2);
}

.login-submit-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(99, 102, 241, 0.3);
}

.login-submit-btn:active {
    transform: translateY(0);
}

.login-footer {
    text-align: center;
    margin-top: 24px;
    font-size: 0.85rem;
    color: var(--text-secondary);
}

.login-footer a {
    color: var(--accent-color);
    font-weight: 600;
    text-decoration: none;
}

.login-footer a:hover {
    text-decoration: underline;
}

/* ========================================== */
/* 3-LEVEL ACCORDION SYLLABUS & MATERIAL ICONS */
/* ========================================== */

.materials-icons-list {
    display: flex;
    align-items: center;
    gap: 8px;
}

.material-icon-btn {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-secondary);
    background: rgba(15, 23, 42, 0.04);
    border: 1px solid var(--card-border);
    cursor: pointer;
    font-size: 0.85rem;
    position: relative;
    transition: var(--transition);
}

.material-icon-btn:hover {
    color: var(--accent-color);
    background: rgba(99, 102, 241, 0.08);
    border-color: var(--accent-color);
    transform: translateY(-2px);
}

/* Tooltip */
.material-icon-btn::after {
    content: attr(data-tooltip);
    position: absolute;
    bottom: calc(100% + 8px);
    left: 50%;
    transform: translateX(-50%) translateY(4px);
    background: #0F172A;
    color: white;
    padding: 6px 10px;
    border-radius: 6px;
    font-size: 0.75rem;
    font-weight: 500;
    white-space: nowrap;
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transition: all 0.15s ease-in-out;
    box-shadow: 0 4px 10px rgba(0,0,0,0.15);
    z-index: 100;
}

.material-icon-btn::before {
    content: '';
    position: absolute;
    bottom: calc(100% + 4px);
    left: 50%;
    transform: translateX(-50%) translateY(4px);
    border: 4px solid transparent;
    border-top-color: #0F172A;
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    transition: all 0.15s ease-in-out;
    z-index: 100;
}

.material-icon-btn:hover::after,
.material-icon-btn:hover::before {
    opacity: 1;
    visibility: visible;
    transform: translateX(-50%) translateY(0);
}

/* Material Lock Overlay */
.material-icon-btn.locked {
    opacity: 0.6;
}

.material-icon-btn.locked::after {
    content: attr(data-tooltip) " (Khóa)";
}

.material-icon-btn.locked i.fa-lock-overlay {
    position: absolute;
    right: -2px;
    bottom: -2px;
    font-size: 0.6rem;
    color: #EF4444;
    background: white;
    border-radius: 50%;
    width: 10px;
    height: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--card-border);
}

/* Edit Mode separating pencil and gear buttons */
.lesson-item-actions {
    display: flex;
    align-items: center;
    gap: 6px;
}

.pencil-btn {
    background: none;
    border: none;
    cursor: pointer;
    color: #475569;
    width: 28px;
    height: 28px;
    border-radius: 50%;
    display: none; /* Shown in edit mode */
    align-items: center;
    justify-content: center;
    transition: var(--transition);
    font-size: 0.85rem;
}

.pencil-btn:hover {
    color: #F59E0B;
    background: #FEF3C7;
}

/* ========================================== */
/* DEDICATED STUDY PAGE (study.html) CSS */
/* ========================================== */

.study-container {
    display: flex;
    min-height: calc(100vh - 80px);
    margin-top: 80px;
    font-family: var(--font-main);
}

.study-sidebar {
    width: 320px;
    border-right: 1px solid var(--card-border);
    background: #FFFFFF;
    height: calc(100vh - 80px);
    position: fixed;
    left: 0;
    overflow-y: auto;
    padding: 24px 16px;
    z-index: 10;
}

.study-main {
    flex-grow: 1;
    margin-left: 320px;
    background: #F8FAFC;
    padding: 40px;
    display: flex;
    flex-direction: column;
    height: calc(100vh - 80px);
    overflow-y: auto;
}

/* Study Tree Styling */
.study-chapter-title {
    font-weight: 700;
    font-size: 0.95rem;
    color: var(--text-primary);
    margin-top: 20px;
    margin-bottom: 8px;
    padding: 0 8px;
    border-left: 3px solid var(--accent-color);
}

.study-lessons-list {
    list-style: none;
    margin-bottom: 16px;
    padding-left: 8px;
}

.study-lesson-title {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-secondary);
    padding: 6px 12px;
    margin-bottom: 4px;
}

.study-materials-list {
    list-style: none;
    padding-left: 12px;
}

.study-material-item a {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 12px;
    border-radius: 8px;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.85rem;
    transition: var(--transition);
    margin-bottom: 2px;
}

.study-material-item a:hover {
    background: rgba(15, 23, 42, 0.03);
    color: var(--text-primary);
}

.study-material-item.active a {
    background: rgba(99, 102, 241, 0.08);
    color: var(--accent-color);
    font-weight: 600;
}

.study-material-item.locked a {
    opacity: 0.5;
    cursor: not-allowed;
}

/* Viewer Panel */
.study-viewer-card {
    background: #FFFFFF;
    border: 1px solid var(--card-border);
    border-radius: 24px;
    padding: 32px;
    box-shadow: var(--shadow-soft);
    flex-grow: 1;
    display: flex;
    flex-direction: column;
    min-height: 450px;
}

.study-content-title {
    font-size: 1.8rem;
    font-weight: 800;
    margin-bottom: 24px;
    color: var(--text-primary);
    border-bottom: 1px solid var(--card-border);
    padding-bottom: 16px;
}

.study-content-body {
    flex-grow: 1;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
}

/* Video Player */
.video-wrapper {
    position: relative;
    padding-bottom: 56.25%;
    height: 0;
    overflow: hidden;
    border-radius: 16px;
    border: 1px solid var(--card-border);
    box-shadow: var(--shadow-soft);
}

.video-wrapper iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: 0;
}

/* PDF Viewer Frame */
.pdf-frame-wrapper {
    flex-grow: 1;
    height: 500px;
    border-radius: 16px;
    overflow: hidden;
    border: 1px solid var(--card-border);
    margin-bottom: 16px;
}

.pdf-frame-wrapper iframe {
    width: 100%;
    height: 100%;
    border: 0;
}

/* Article Styling */
.article-content {
    line-height: 1.7;
    font-size: 1.05rem;
    color: #334155;
}

.article-content h3 {
    margin: 24px 0 12px 0;
    color: var(--text-primary);
}

.article-content p {
    margin-bottom: 16px;
}

/* Navigation buttons */
.study-nav-bar {
    display: flex;
    justify-content: space-between;
    margin-top: 24px;
    padding-top: 20px;
    border-top: 1px solid var(--card-border);
}

/* Responsive adjustment for study container */
@media (max-width: 992px) {
    .study-sidebar {
        display: none;
    }
    .study-main {
        margin-left: 0;
        padding: 20px;
    }
}

/* Hover style cho học liệu dạng cây thụt lề */
.material-sub-item:hover {
    background: rgba(99, 102, 241, 0.06);
}
.material-sub-item:hover span {
    color: var(--accent-color) !important;
}
.material-sub-item.locked:hover {
    background: rgba(239, 68, 68, 0.04);
}
/* Breadcrumb Links Custom Styles */
.lesson-breadcrumb a {
    color: var(--text-secondary);
    text-decoration: none;
    transition: all 0.2s ease;
}
.lesson-breadcrumb a:hover {
    color: var(--accent-color);
    text-decoration: underline;
}
.lesson-breadcrumb span {
    color: var(--text-secondary);
}