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

html {
    scroll-behavior: smooth;
    overflow-x: hidden;
}

:root {
    /* Light theme (default) */
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-tertiary: #f0f1f3;
    --text-primary: #1a1a1a;
    --text-secondary: #666666;
    --text-tertiary: #999999;
    --accent-dark: #1a1a1a;
    --accent-tech: #2d2d2d;
    --accent-gradient: linear-gradient(135deg, #2d2d2d 0%, #1a1a1a 100%);
    --border-color: rgba(0, 0, 0, 0.08);
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.04);
    --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 16px 48px rgba(0, 0, 0, 0.12);
    --card-bg: #ffffff;
    --video-bg: linear-gradient(135deg, rgba(45, 45, 45, 0.06) 0%, rgba(26, 26, 26, 0.04) 100%);
    --video-border: rgba(45, 45, 45, 0.15);
    --quote-bg: linear-gradient(135deg, rgba(45, 45, 45, 0.06) 0%, rgba(26, 26, 26, 0.04) 100%);
    --quote-border: #2d2d2d;
}

[data-theme="dark"] {
    /* Dark theme */
    --bg-primary: #0a0a0a;
    --bg-secondary: #111111;
    --bg-tertiary: #1a1a1a;
    --text-primary: #ffffff;
    --text-secondary: rgba(255, 255, 255, 0.7);
    --text-tertiary: rgba(255, 255, 255, 0.5);
    --accent-dark: #e5e5e5;
    --accent-tech: #b0b0b0;
    --accent-gradient: linear-gradient(135deg, #b0b0b0 0%, #e5e5e5 100%);
    --border-color: rgba(255, 255, 255, 0.1);
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 16px 48px rgba(0, 0, 0, 0.5);
    --card-bg: rgba(255, 255, 255, 0.03);
    --video-bg: linear-gradient(135deg, rgba(176, 176, 176, 0.08) 0%, rgba(229, 229, 229, 0.04) 100%);
    --video-border: rgba(255, 255, 255, 0.15);
    --quote-bg: linear-gradient(135deg, rgba(176, 176, 176, 0.08) 0%, rgba(229, 229, 229, 0.04) 100%);
    --quote-border: #b0b0b0;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Inter', -apple-system, sans-serif;
    line-height: 1.7;
    background: var(--bg-primary);
    color: var(--text-primary);
    font-size: 17px;
    transition: background 0.3s ease, color 0.3s ease;
}

/* Navigation */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    padding: 16px 0;
    transition: all 0.3s ease;
}

[data-theme="dark"] .nav {
    background: rgba(10, 10, 10, 0.9);
}

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

.nav-content {
    max-width: 100%;
    margin: 0;
    padding: 16px 32px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-logo {
    font-weight: 700;
    font-size: 20px;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* Hero Section */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 120px 24px 80px;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    right: -10%;
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, rgba(45, 45, 45, 0.08) 0%, transparent 70%);
    border-radius: 50%;
    pointer-events: none;
    transition: opacity 0.3s ease;
}

[data-theme="dark"] .hero::before {
    background: radial-gradient(circle, rgba(176, 176, 176, 0.06) 0%, transparent 70%);
}

.hero::after {
    content: '';
    position: absolute;
    bottom: -30%;
    left: -10%;
    width: 500px;
    height: 500px;
    background: radial-gradient(circle, rgba(26, 26, 26, 0.08) 0%, transparent 70%);
    border-radius: 50%;
    pointer-events: none;
    transition: opacity 0.3s ease;
}

[data-theme="dark"] .hero::after {
    background: radial-gradient(circle, rgba(229, 229, 229, 0.04) 0%, transparent 70%);
}

.hero-content {
    max-width: 900px;
    position: relative;
    z-index: 1;
    opacity: 0;
    transform: translateY(30px);
    animation: fadeInUp 1s ease forwards;
    margin-top: 40px;
}

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

.hero h1.hero-title {
    font-weight: 800;
    line-height: 1.2;
    margin-bottom: 24px;
    text-align: center;
}

.hero-title-main {
    display: block;
    font-size: clamp(36px, 6vw, 64px);
    font-weight: 900;
    color: var(--text-primary);
    letter-spacing: -0.02em;
}

.hero-title-sub {
    display: block;
    font-size: clamp(32px, 4.5vw, 54px);
    font-weight: 700;
    font-style: italic;
    color: var(--text-primary);
    /* margin-top: 2px; */
    letter-spacing: 0;
}

.hero-title-third {
    display: block;
    font-size: clamp(20px, 2.5vw, 38px);
    font-weight: 700;
    font-style: italic;
    color: var(--text-primary);
    /* margin-top: 0; */
    letter-spacing: 0;
}

.hero-title-accent {
    font-weight: 700;
    color: var(--text-primary);
}

.hero-description {
    font-size: 18px;
    color: var(--text-secondary);
    max-width: 700px;
    margin: 0 auto 40px;
    line-height: 1.8;
}

.hero-description strong {
    color: var(--text-primary);
    font-weight: 600;
}

.cta-buttons {
    display: flex;
    gap: 16px;
    justify-content: center;
    flex-wrap: wrap;
    margin-top: 40px;
}

.cta-button {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 24px;
    background: transparent;
    color: var(--accent-dark);
    border: 1px solid var(--accent-dark);
    text-decoration: none;
    border-radius: 8px;
    font-weight: 500;
    font-size: 15px;
    transition: all 0.3s ease;
}

.cta-button:hover {
    background: var(--accent-dark);
    color: var(--bg-primary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

[data-theme="dark"] .cta-button {
    color: rgba(255, 255, 255, 0.85);
    border-color: rgba(255, 255, 255, 0.3);
}

[data-theme="dark"] .cta-button:hover {
    background: rgba(255, 255, 255, 0.15);
    color: #ffffff;
    border-color: rgba(255, 255, 255, 0.6);
    box-shadow: 0 4px 16px rgba(255, 255, 255, 0.1);
}

/* Quick Navigation */
.quick-nav {
    position: fixed;
    left: 32px;
    top: 50%;
    transform: translateY(-50%);
    width: 180px;
    z-index: 100;
}

.quick-nav-content {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.quick-nav-link {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px;
    background: transparent;
    border: none;
    border-radius: 8px;
    text-decoration: none;
    color: var(--text-secondary);
    transition: all 0.3s ease;
    font-size: 14px;
}

.quick-nav-link:hover {
    background: var(--bg-secondary);
    color: var(--text-primary);
}

.quick-nav-link.active {
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-weight: 600;
}

[data-theme="dark"] .quick-nav-link.active {
    background: rgba(255, 255, 255, 0.1);
    border-left: 3px solid rgba(255, 255, 255, 0.6);
    padding-left: 13px;
}

[data-theme="dark"] .quick-nav-link.active .quick-nav-number {
    opacity: 1;
    color: rgba(255, 255, 255, 0.8);
}

.quick-nav-number {
    font-size: 11px;
    font-weight: 600;
    opacity: 0.5;
    min-width: 20px;
}

.quick-nav-text {
    font-size: 14px;
    font-weight: 500;
}

/* Section */
.section {
    padding: 100px 24px;
    max-width: 900px;
    margin: 0 auto;
}

.section.intro-description {
    padding: 60px 24px 40px;
}

.section-header {
    margin-bottom: 60px;
}

.section-label {
    display: inline-block;
    font-size: 12px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1px;
    color: var(--accent-tech);
    margin-bottom: 16px;
}

.section h2 {
    font-size: clamp(28px, 4vw, 38px);
    font-weight: 700;
    letter-spacing: -0.02em;
    margin-bottom: 20px;
    line-height: 1.2;
}

.section h3 {
    font-size: 22px;
    font-weight: 600;
    margin-bottom: 16px;
    margin-top: 32px;
}

.section p {
    font-size: 17px;
    color: var(--text-secondary);
    line-height: 1.8;
    margin-bottom: 20px;
}

/* Content Card */
.content-card {
    background: var(--card-bg);
    border-radius: 20px;
    padding: 40px;
    margin-top: 40px;
    border: 1px solid var(--border-color);
    transition: all 0.3s ease;
}

.content-card:hover {
    box-shadow: var(--shadow-sm);
}

/* Video Grid */
.video-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 24px;
    margin: 32px 0;
}

/* Media Container */
.media-container {
    border-radius: 16px;
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: all 0.3s ease;
}

.media-container:hover {
    box-shadow: var(--shadow-md);
}

.media-container img,
.media-container video {
    width: 100%;
    height: auto;
    display: block;
}

.media-caption {
    padding: 16px 20px;
    background: var(--bg-secondary);
    font-size: 14px;
    color: var(--text-secondary);
    font-weight: 500;
}

/* Video Placeholder */
.video-placeholder {
    aspect-ratio: 16/9;
    background: var(--video-bg);
    border-radius: 16px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    border: 2px dashed var(--video-border);
    transition: all 0.3s ease;
}

.video-placeholder:hover {
    border-color: var(--accent-tech);
}

.video-icon {
    width: 64px;
    height: 64px;
    background: var(--accent-gradient);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 16px;
}

.video-icon svg {
    width: 28px;
    height: 28px;
    fill: white;
}

.video-label {
    font-size: 14px;
    color: var(--text-secondary);
    font-weight: 500;
}

/* Numbered Sections */
.numbered-section {
    display: grid;
    grid-template-columns: auto minmax(0, 1fr);
    gap: 24px;
    margin: 60px 0;
}

.section-number {
    font-size: 72px;
    font-weight: 800;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1;
}

.section-content {
    padding-top: 8px;
}

/* Quote */
.quote-box {
    background: var(--quote-bg);
    border-left: 4px solid var(--quote-border);
    padding: 32px;
    border-radius: 0 16px 16px 0;
    margin: 8px 0;
}

.quote-text {
    font-size: 20px;
    font-weight: 500;
    font-style: italic;
    color: var(--text-primary);
    line-height: 1.6;
}

/* Possibilities Grid */
.possibilities-grid {
    display: flex;
    flex-direction: column;
    gap: 60px;
    margin: 40px 0;
}

.possibility-item {
    display: grid;
    grid-template-columns: auto 1fr;
    gap: 24px;
    align-items: start;
}

.possibility-number {
    width: 34px;
    height: 34px;
    background: var(--accent-gradient);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    font-weight: 700;
    color: white;
    flex-shrink: 0;
}

.possibility-content {
    flex: 1;
}

.possibility-content h3 {
    font-size: 17px;
    font-weight: 600;
    margin-bottom: 8px;
    margin-top: 0;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 12px;
}

.possibility-emoji {
    font-size: 28px;
}

.possibility-content p {
    font-size: 16px;
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 20px;
}

.possibility-note {
    background: none;
    border-radius: 0;
    padding: 0;
    font-size: 15px;
    color: var(--text-secondary);
    border-left: none;
    margin-bottom: 12px;
}

/* Enhanced Video Container */
.enhanced-video {
    position: relative;
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    overflow: hidden;
    transition: all 0.3s ease;
}

.enhanced-video:hover {
    box-shadow: var(--shadow-md);
    border-color: var(--accent-tech);
}

.video-wrapper {
    position: relative;
    width: 100%;
    aspect-ratio: 16/9;
    border-radius: 16px;
    overflow: hidden;
    background: #000;
}

.video-wrapper::after {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(to top, rgba(0,0,0,0.3) 0%, transparent 30%);
    pointer-events: none;
}

.enhanced-video video {
    width: 100%;
    height: 100%;
    display: block;
    object-fit: cover;
}

.video-play-button {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 48px;
    height: 48px;
    background: rgba(255, 255, 255, 0.95);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.25s ease;
    z-index: 10;
    box-shadow: 0 3px 10px rgba(0, 0, 0, 0.2);
}

.enhanced-video:hover .video-play-button:not(.hidden) {
    transform: translate(-50%, -50%) scale(1.1);
}

.video-play-button.hidden {
    opacity: 0;
    pointer-events: none;
}

.video-play-button:hover {
    background: white;
    box-shadow: 0 5px 16px rgba(0, 0, 0, 0.3);
}

.video-play-button svg {
    width: 18px;
    height: 18px;
    fill: var(--accent-tech);
    margin-left: 2px;
    transition: transform 0.2s ease;
}

.video-caption {
    padding: 14px 20px;
    background: var(--bg-secondary);
    font-size: 14px;
    color: var(--text-secondary);
    font-weight: 500;
}

/* Module Cards (Section 5) */
.module-list {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.module-card {
    padding: 24px 28px;
    border-left: 3px solid var(--accent-tech);
    background: var(--bg-secondary);
    border-radius: 0 12px 12px 0;
    transition: all 0.3s ease;
}

.module-card:hover {
    box-shadow: var(--shadow-sm);
}

.module-card h3 {
    font-size: 17px;
    font-weight: 600;
    margin: 0 0 10px;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 10px;
    flex-wrap: wrap;
}

.module-tag {
    font-size: 12px;
    font-weight: 500;
    color: var(--text-tertiary);
    background: var(--bg-tertiary);
    padding: 2px 8px;
    border-radius: 4px;
}

.module-card p {
    font-size: 15px;
    color: var(--text-secondary);
    line-height: 1.8;
    margin: 0;
}

/* Video Showcase Carousel */
.video-showcase {
    display: flex;
    overflow: visible;
    gap: 20px;
}

.video-showcase::-webkit-scrollbar {
    display: none;
}

.video-showcase .enhanced-video {
    flex: 0 0 calc(50% - 10px);
    min-width: calc(50% - 10px);
    max-width: calc(50% - 10px);
    scroll-snap-align: start;
    transition: transform 0.4s ease;
}

/* Carousel Wrapper */
.carousel-wrapper {
    position: relative;
    overflow: hidden;
    padding: 0 20px;
    margin: 0 -20px;
}

.carousel-arrow {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: rgba(0, 0, 0, 0.55);
    border: none;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.25);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    z-index: 10;
    transition: all 0.2s ease;
    color: #fff;
    font-size: 20px;
    padding: 0;
    line-height: 1;
    backdrop-filter: blur(4px);
}

.carousel-arrow:hover {
    background: rgba(0, 0, 0, 0.75);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.35);
    transform: translateY(-50%) scale(1.08);
}

[data-theme="dark"] .carousel-arrow {
    background: rgba(255, 255, 255, 0.55);
    color: #000;
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.4);
}

[data-theme="dark"] .carousel-arrow:hover {
    background: rgba(255, 255, 255, 0.75);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.5);
}

.carousel-arrow.hidden {
    opacity: 0;
    pointer-events: none;
}

.carousel-arrow-left {
    left: 2px;
}

.carousel-arrow-right {
    right: 2px;
}

.carousel-dots {
    display: flex;
    justify-content: center;
    gap: 8px;
    margin-top: 12px;
}

.carousel-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: var(--border-color);
    border: none;
    padding: 0;
    cursor: pointer;
    transition: all 0.2s ease;
}

.carousel-dot.active {
    background: var(--accent-tech);
    transform: scale(1.2);
}

/* Scroll animations */
.reveal {
    opacity: 0;
    transform: translateY(40px);
    transition: all 0.8s cubic-bezier(0.4, 0, 0.2, 1);
}

.reveal.visible {
    opacity: 1;
    transform: translateY(0);
}

/* Floating Theme Toggle Button */
.theme-toggle-floating {
    position: fixed;
    bottom: 32px;
    right: 32px;
    width: 56px;
    height: 56px;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    box-shadow: var(--shadow-lg);
    transition: all 0.3s ease;
    z-index: 1000;
}

.theme-toggle-floating:hover {
    transform: scale(1.1);
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.2);
}

.theme-toggle-floating:active {
    transform: scale(0.95);
}

/* Section 6: Table scroll */
#section3 .table-scroll-wrapper {
    overflow-x: auto;
    overflow-y: hidden;
    -webkit-overflow-scrolling: touch;
}

/* Section 5: Smaller items */
#section4 .possibility-content p {
    font-size: 14px;
    margin-bottom: 12px;
}

/* Responsive */
@media (max-width: 768px) {
    .quick-nav {
        display: none;
    }

    .section {
        padding: 60px 24px;
    }

    .section.intro-description {
        padding: 40px 24px 20px;
    }

    .hero {
        padding: 100px 24px 60px;
    }

    .numbered-section {
        grid-template-columns: 1fr;
    }

    .section-number {
        font-size: 48px;
    }

    .content-card {
        padding: 24px;
    }

    .possibility-item {
        grid-template-columns: 1fr;
        gap: 16px;
    }

    .possibility-content h3 {
        font-size: 18px;
    }

    .video-showcase .enhanced-video {
        flex: 1 0 100%;
        max-width: 100%;
    }

    .carousel-arrow-left {
        left: 2px;
    }

    .carousel-arrow-right {
        right: 2px;
    }
}

@media (max-width: 480px) {
}