/* ========================================
   CSS Variables
   ======================================== */
:root {
    /* Colors - Inspired by modern EdTech platforms */
    --color-white: #FFFFFF;
    --color-background: #FAFBFC;
    --color-section-bg: #F5F7FA;
    --color-primary-text: #1A1D29;
    --color-secondary-text: #6B7594;
    --color-accent: #6366F1;
    --color-accent-light: #818CF8;
    --color-accent-dark: #4F46E5;
    --color-gradient-start: #6366F1;
    --color-gradient-end: #8B5CF6;
    
    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-size-hero: 48px;
    --font-size-section: 32px;
    --font-size-body: 16px;
    
    /* Spacing */
    --spacing-section: 100px;
    --spacing-container: 80px;
    
    /* Effects */
    --border-radius: 16px;
    --border-radius-small: 12px;
    --transition: all 0.3s ease;
    --box-shadow: 0 4px 20px rgba(99, 102, 241, 0.08);
    --box-shadow-hover: 0 12px 40px rgba(99, 102, 241, 0.15);
    --box-shadow-card: 0 2px 12px rgba(26, 29, 41, 0.04);
}

/* ========================================
   Base Styles
   ======================================== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-body);
    line-height: 1.6;
    color: var(--color-primary-text);
    background-color: var(--color-background);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

/* ========================================
   Typography
   ======================================== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.2;
    color: var(--color-primary-text);
}

p {
    margin-bottom: 16px;
}

a {
    text-decoration: none;
    color: inherit;
    transition: var(--transition);
}

/* ========================================
   Header / Navigation
   ======================================== */
.header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background-color: var(--color-white);
    z-index: 1000;
    transition: var(--transition);
}

.header.scrolled {
    box-shadow: var(--box-shadow);
}

.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 70px;
}

.nav__logo a {
    font-size: 20px;
    font-weight: 600;
    color: var(--color-primary-text);
}

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

.nav__link {
    font-size: 15px;
    font-weight: 500;
    color: var(--color-secondary-text);
    transition: var(--transition);
}

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

.nav__link--cta {
    color: var(--color-accent);
    padding: 8px 20px;
    border: 2px solid var(--color-accent);
    border-radius: 8px;
}

.nav__link--cta:hover {
    background-color: var(--color-accent);
    color: var(--color-white);
}

.nav__toggle {
    display: none;
    background: none;
    border: none;
    font-size: 24px;
    cursor: pointer;
    color: var(--color-primary-text);
}

/* ========================================
   Buttons
   ======================================== */
.btn {
    display: inline-block;
    padding: 14px 32px;
    font-size: 15px;
    font-weight: 500;
    border-radius: 10px;
    transition: var(--transition);
    cursor: pointer;
    border: 2px solid transparent;
}

.btn--primary {
    background: linear-gradient(135deg, var(--color-gradient-start) 0%, var(--color-gradient-end) 100%);
    color: var(--color-white);
    position: relative;
    overflow: hidden;
}

.btn--primary::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s;
}

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

.btn--primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 12px 32px rgba(99, 102, 241, 0.35);
}

.btn--secondary {
    background-color: transparent;
    color: var(--color-accent);
    border-color: var(--color-accent);
}

.btn--secondary:hover {
    background-color: var(--color-accent);
    color: var(--color-white);
}

.btn--large {
    padding: 16px 40px;
    font-size: 16px;
}

/* ========================================
   Sections
   ======================================== */
.section {
    padding: var(--spacing-section) 0;
}

.section--gray {
    background-color: var(--color-section-bg);
}

.section__header {
    text-align: center;
    margin-bottom: 60px;
}

.section__title {
    font-size: var(--font-size-section);
    margin-bottom: 16px;
}

.section__subtitle {
    font-size: 18px;
    color: var(--color-secondary-text);
    max-width: 600px;
    margin: 0 auto;
}

/* ========================================
   Hero Section
   ======================================== */
.hero {
    padding: 140px 0 100px;
    background: linear-gradient(135deg, #F5F7FA 0%, #FAFBFC 100%);
    position: relative;
}

.hero::before {
    content: '';
    position: absolute;
    top: 0;
    right: 0;
    width: 50%;
    height: 100%;
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.03) 0%, rgba(139, 92, 246, 0.05) 100%);
    pointer-events: none;
    z-index: 0;
}

.hero .container {
    position: relative;
    z-index: 1;
}

.hero__content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: center;
}

.hero__title {
    font-size: var(--font-size-hero);
    margin-bottom: 16px;
}

.hero__subtitle {
    font-size: 24px;
    color: var(--color-accent);
    margin-bottom: 20px;
}

.hero__description {
    font-size: 18px;
    color: var(--color-secondary-text);
    margin-bottom: 32px;
    line-height: 1.7;
}

.hero__buttons {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
}

.hero__image {
    display: flex;
    justify-content: center;
    align-items: center;
}

.hero__photo {
    width: 400px;
    height: 400px;
    object-fit: cover;
    border-radius: 24px;
    box-shadow: 0 20px 60px rgba(99, 102, 241, 0.25);
}

.hero__placeholder {
    width: 400px;
    height: 400px;
    background: linear-gradient(135deg, var(--color-gradient-start) 0%, var(--color-gradient-end) 100%);
    border-radius: 24px;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 20px 60px rgba(99, 102, 241, 0.25);
    position: relative;
    overflow: hidden;
}

.hero__placeholder::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle, rgba(255, 255, 255, 0.1) 0%, transparent 70%);
    animation: shimmer 8s infinite;
}

@keyframes shimmer {
    0%, 100% {
        transform: translate(-25%, -25%) rotate(0deg);
    }
    50% {
        transform: translate(-25%, -25%) rotate(180deg);
    }
}

.hero__placeholder i {
    font-size: 120px;
    color: rgba(255, 255, 255, 0.9);
}

/* ========================================
   About Section
   ======================================== */
.about__content {
    max-width: 900px;
    margin: 0 auto;
}

.about__text {
    font-size: 17px;
    line-height: 1.8;
    color: var(--color-secondary-text);
    margin-bottom: 24px;
}

/* ========================================
   Subjects Section
   ======================================== */
.subjects__grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 32px;
}

.card {
    background-color: var(--color-white);
    padding: 40px 32px;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow-card);
    transition: var(--transition);
    text-align: center;
    border: 1px solid rgba(99, 102, 241, 0.08);
    position: relative;
    overflow: hidden;
}

.card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 4px;
    background: linear-gradient(90deg, var(--color-gradient-start), var(--color-gradient-end));
    transform: scaleX(0);
    transition: transform 0.3s ease;
}

.card:hover::before {
    transform: scaleX(1);
}

.card:hover {
    transform: translateY(-8px);
    box-shadow: var(--box-shadow-hover);
    border-color: rgba(99, 102, 241, 0.2);
}

.card__icon {
    width: 64px;
    height: 64px;
    margin: 0 auto 24px;
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(139, 92, 246, 0.15));
    border-radius: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
}

.card:hover .card__icon {
    transform: scale(1.1) rotate(5deg);
}

.card__icon i {
    font-size: 28px;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.card__title {
    font-size: 22px;
    margin-bottom: 16px;
}

.card__text {
    font-size: 15px;
    color: var(--color-secondary-text);
    line-height: 1.6;
}

/* ========================================
   Teaching Approach Section
   ======================================== */
.approach__grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 40px;
    max-width: 1000px;
    margin: 0 auto;
}

.approach__item {
    display: flex;
    gap: 20px;
}

.approach__icon {
    flex-shrink: 0;
    width: 56px;
    height: 56px;
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(139, 92, 246, 0.1));
    border-radius: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.approach__icon i {
    font-size: 24px;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.approach__title {
    font-size: 20px;
    margin-bottom: 8px;
}

.approach__text {
    font-size: 15px;
    color: var(--color-secondary-text);
    line-height: 1.6;
}

/* ========================================
   Qualifications Section
   ======================================== */
.qualifications__content {
    max-width: 900px;
    margin: 0 auto;
}

.qualification {
    display: flex;
    gap: 24px;
    margin-bottom: 40px;
    padding: 32px;
    background-color: var(--color-white);
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow-card);
    border: 1px solid rgba(99, 102, 241, 0.08);
    transition: var(--transition);
}

.qualification:hover {
    box-shadow: var(--box-shadow);
    border-color: rgba(99, 102, 241, 0.15);
}

.qualification:last-child {
    margin-bottom: 0;
}

.qualification__icon {
    flex-shrink: 0;
    width: 64px;
    height: 64px;
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(139, 92, 246, 0.15));
    border-radius: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.qualification__icon i {
    font-size: 28px;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.qualification__title {
    font-size: 22px;
    margin-bottom: 12px;
}

.qualification__text {
    font-size: 15px;
    color: var(--color-secondary-text);
    line-height: 1.7;
}

/* ========================================
   Materials Section
   ======================================== */
.materials__grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
}

.material-card {
    background-color: var(--color-white);
    padding: 32px 24px;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow-card);
    text-align: center;
    transition: var(--transition);
    cursor: pointer;
    border: 1px solid rgba(99, 102, 241, 0.08);
    display: flex;
    flex-direction: column;
}

.material-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--box-shadow-hover);
    border-color: rgba(99, 102, 241, 0.2);
}

.material-link {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    margin-top: 16px;
    padding: 10px 20px;
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(139, 92, 246, 0.1));
    color: var(--color-accent);
    border-radius: 8px;
    font-size: 14px;
    font-weight: 500;
    text-decoration: none;
    transition: var(--transition);
    border: 1px solid rgba(99, 102, 241, 0.2);
}

.material-link:hover {
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    color: var(--color-white);
    border-color: transparent;
    transform: scale(1.05);
}

.material-link i {
    font-size: 12px;
}

.material-card__icon {
    width: 56px;
    height: 56px;
    margin: 0 auto 20px;
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(139, 92, 246, 0.15));
    border-radius: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.material-card__icon i {
    font-size: 24px;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.material-card__title {
    font-size: 18px;
    margin-bottom: 12px;
}

.material-card__text {
    font-size: 14px;
    color: var(--color-secondary-text);
    line-height: 1.5;
}

/* ========================================
   Reviews Section
   ======================================== */
.reviews__container {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
    padding: 0 60px;
}

.reviews__slider {
    position: relative;
    min-height: 220px;
}

.review-card {
    display: none;
    background-color: var(--color-white);
    padding: 48px;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow-card);
    text-align: center;
    border: 1px solid rgba(99, 102, 241, 0.08);
    position: relative;
}

.review-card::before {
    content: '"';
    position: absolute;
    top: 24px;
    left: 32px;
    font-size: 80px;
    font-family: Georgia, serif;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    opacity: 0.15;
    line-height: 1;
}

.review-card.active {
    display: block;
    animation: fadeIn 0.5s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.review-card__text {
    font-size: 17px;
    line-height: 1.7;
    color: var(--color-secondary-text);
    margin-bottom: 24px;
    font-style: italic;
}

.review-card__author {
    font-size: 15px;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    font-weight: 600;
}

.reviews__nav {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    width: 44px;
    height: 44px;
    background-color: var(--color-white);
    border: 2px solid rgba(99, 102, 241, 0.2);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: var(--transition);
    font-size: 16px;
    box-shadow: var(--box-shadow-card);
}

.reviews__nav:hover {
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    border-color: transparent;
    color: var(--color-white);
    transform: translateY(-50%) scale(1.1);
}

.reviews__nav--prev {
    left: 0;
}

.reviews__nav--next {
    right: 0;
}

.reviews__dots {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin-top: 32px;
}

.review-dot {
    width: 10px;
    height: 10px;
    border-radius: 50%;
    background-color: #D1D5DB;
    cursor: pointer;
    transition: var(--transition);
}

.review-dot.active {
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    width: 28px;
    border-radius: 5px;
}

/* ========================================
   Lesson Format Section
   ======================================== */
.lesson-format__content {
    max-width: 800px;
    margin: 0 auto;
}

.lesson-format__grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 32px;
    margin-bottom: 40px;
}

.format-item {
    background-color: var(--color-white);
    padding: 32px;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow-card);
    text-align: center;
    border: 1px solid rgba(99, 102, 241, 0.08);
    transition: var(--transition);
}

.format-item:hover {
    box-shadow: var(--box-shadow);
    border-color: rgba(99, 102, 241, 0.15);
}

.format-item__icon {
    width: 64px;
    height: 64px;
    margin: 0 auto 20px;
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(139, 92, 246, 0.15));
    border-radius: 16px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.format-item__icon i {
    font-size: 28px;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.format-item__title {
    font-size: 22px;
    margin-bottom: 12px;
}

.format-item__text {
    font-size: 15px;
    color: var(--color-secondary-text);
    line-height: 1.6;
}

.lesson-format__details {
    background-color: var(--color-white);
    padding: 32px;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow-card);
    border: 1px solid rgba(99, 102, 241, 0.08);
}

.lesson-format__details p {
    font-size: 16px;
    color: var(--color-secondary-text);
    margin-bottom: 12px;
}

.lesson-format__details p:last-child {
    margin-bottom: 0;
}

/* ========================================
   Contact Section
   ======================================== */
.contact__content {
    max-width: 700px;
    margin: 0 auto;
    text-align: center;
}

.contact__methods {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
    margin-bottom: 40px;
}

.contact__method {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 20px 24px;
    background-color: var(--color-white);
    border-radius: var(--border-radius-small);
    box-shadow: var(--box-shadow-card);
    transition: var(--transition);
    color: var(--color-secondary-text);
    border: 1px solid rgba(99, 102, 241, 0.08);
}

.contact__method:hover {
    transform: translateY(-4px);
    box-shadow: var(--box-shadow-hover);
    color: var(--color-primary-text);
    border-color: rgba(99, 102, 241, 0.2);
}

.contact__method i {
    font-size: 20px;
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.contact__cta {
    margin-top: 40px;
}

/* ========================================
   Footer
   ======================================== */
.footer {
    background-color: var(--color-primary-text);
    color: var(--color-white);
    padding: 40px 0;
}

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

.footer__text {
    font-size: 14px;
    color: rgba(255, 255, 255, 0.7);
}

.footer__social {
    display: flex;
    gap: 20px;
}

.footer__social-link {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: rgba(255, 255, 255, 0.1);
    border-radius: 50%;
    transition: var(--transition);
}

.footer__social-link:hover {
    background: linear-gradient(135deg, var(--color-gradient-start), var(--color-gradient-end));
    transform: translateY(-3px);
}

.footer__social-link i {
    font-size: 18px;
}

/* ========================================
   Responsive Design
   ======================================== */

/* Tablet */
@media (max-width: 992px) {
    :root {
        --font-size-hero: 40px;
        --font-size-section: 28px;
        --spacing-section: 80px;
    }
    
    .hero__content {
        grid-template-columns: 1fr;
        gap: 40px;
    }
    
    .hero__photo,
    .hero__placeholder {
        width: 300px;
        height: 300px;
    }
    
    .subjects__grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .approach__grid {
        grid-template-columns: 1fr;
    }
    
    .materials__grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* Mobile */
@media (max-width: 768px) {
    :root {
        --font-size-hero: 32px;
        --font-size-section: 24px;
        --spacing-section: 60px;
    }
    
    .container {
        padding: 0 20px;
    }
    
    /* Navigation */
    .nav__menu {
        position: fixed;
        top: 70px;
        right: -100%;
        width: 80%;
        max-width: 300px;
        height: calc(100vh - 70px);
        background-color: var(--color-white);
        flex-direction: column;
        align-items: flex-start;
        padding: 40px 24px;
        box-shadow: var(--box-shadow);
        transition: right 0.3s ease;
        gap: 24px;
    }
    
    .nav__menu.active {
        right: 0;
    }
    
    .nav__toggle {
        display: block;
    }
    
    /* Hero */
    .hero {
        padding: 100px 0 60px;
    }
    
    .hero__buttons {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
        text-align: center;
    }
    
    .hero__photo,
    .hero__placeholder {
        width: 250px;
        height: 250px;
    }
    
    .hero__placeholder i {
        font-size: 80px;
    }
    
    /* Sections */
    .subjects__grid,
    .materials__grid {
        grid-template-columns: 1fr;
    }
    
    .lesson-format__grid,
    .contact__methods {
        grid-template-columns: 1fr;
    }
    
    .qualification {
        flex-direction: column;
    }
    
    /* Reviews */
    .reviews__container {
        padding: 0 50px;
    }
    
    .reviews__nav {
        width: 36px;
        height: 36px;
        font-size: 14px;
    }
    
    /* Footer */
    .footer__content {
        flex-direction: column;
        gap: 20px;
        text-align: center;
    }
}

@media (max-width: 480px) {
    :root {
        --font-size-hero: 28px;
        --font-size-section: 22px;
    }
    
    .hero__photo,
    .hero__placeholder {
        width: 200px;
        height: 200px;
    }
    
    .hero__placeholder i {
        font-size: 60px;
    }
    
    .card,
    .qualification,
    .format-item {
        padding: 24px 20px;
    }
    
    .reviews__container {
        padding: 0 40px;
    }
    
    .review-card {
        padding: 28px 20px;
    }
}