:root {
    /* Colors */
    --color-primary: #0066FF;
    --color-secondary: #00FF88;
    --color-accent: #6B46C1;
    --color-bg: #0A0E27;
    --color-bg-light: #1A1F3A;
    --color-text: #FFFFFF;
    --color-text-muted: #A0AEC0;
    --color-border: rgba(255, 255, 255, 0.1);
    
    /* Typography */
    --font-primary: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, sans-serif;
    --font-secondary: 'Inter', sans-serif;
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 2rem;
    --spacing-lg: 4rem;
    --spacing-xl: 6rem;
    
    /* Border Radius */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    
    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-base: 0.3s ease;
    --transition-slow: 0.5s ease;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-primary);
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    overflow-x: hidden;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

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

ul {
    list-style: none;
}

/* Container */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* Navigation */
.nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background-color: rgba(10, 14, 39, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--color-border);
    transition: var(--transition-base);
}

.nav--scrolled {
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
}

.nav__container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-sm) var(--spacing-md);
}

.nav__logo {
    background: rgba(255, 255, 255, 0.95);
    padding: 8px 16px;
    border-radius: var(--radius-md);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
    transition: var(--transition-base);
}

.nav__logo:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
}

.nav__logo-img {
    height: 40px;
    width: auto;
}

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

.nav__menu {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
}

.nav__list {
    display: flex;
    gap: var(--spacing-md);
}

.nav__link {
    padding: var(--spacing-xs) var(--spacing-sm);
    color: var(--color-text-muted);
    font-weight: 500;
    transition: var(--transition-fast);
}

.nav__link:hover,
.nav__link--active {
    color: var(--color-primary);
}

.nav__lang-toggle {
    background: var(--color-primary);
    border: none;
    color: var(--color-text);
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-weight: 600;
    transition: var(--transition-fast);
}

.nav__lang-toggle:hover {
    background: #0052cc;
}

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

.hero__bg {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 1;
}

.hero__bg-img {
    width: 100%;
    height: 100%;
    object-fit: cover;
    object-position: center;
}

.hero__overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, rgba(10, 14, 39, 0.85) 0%, rgba(26, 31, 58, 0.7) 100%);
    z-index: 2;
}

.hero__container {
    position: relative;
    z-index: 3;
    padding-top: 80px;
    padding-bottom: 80px;
}

.hero__content {
    max-width: 800px;
    text-align: center;
    margin: 0 auto;
}

.hero__title {
    font-family: var(--font-secondary);
    font-size: clamp(2rem, 5vw, 3.5rem);
    font-weight: 700;
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero__subtitle {
    font-size: clamp(1rem, 2.5vw, 1.25rem);
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-lg);
}

.hero__cta {
    display: flex;
    gap: var(--spacing-sm);
    justify-content: center;
    flex-wrap: wrap;
}

.hero__scroll {
    position: absolute;
    bottom: var(--spacing-md);
    left: 50%;
    transform: translateX(-50%);
    z-index: 3;
    animation: bounce 2s infinite;
}

.hero__scroll i {
    font-size: 2rem;
    color: var(--color-primary);
}

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

/* Buttons */
.btn {
    display: inline-block;
    padding: 14px 32px;
    border-radius: var(--radius-md);
    font-weight: 600;
    text-align: center;
    cursor: pointer;
    transition: var(--transition-base);
    border: 2px solid transparent;
}

.btn--primary {
    background: var(--color-primary);
    color: var(--color-text);
}

.btn--primary:hover {
    background: #0052cc;
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(0, 102, 255, 0.3);
}

.btn--outline {
    border-color: var(--color-primary);
    color: var(--color-primary);
}

.btn--outline:hover {
    background: var(--color-primary);
    color: var(--color-text);
}

/* Section */
.section {
    padding: var(--spacing-xl) 0;
}

.section--vision {
    background: linear-gradient(135deg, var(--color-bg-light) 0%, var(--color-bg) 100%);
}

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

.section--ssirn {
    background: linear-gradient(135deg, rgba(0, 102, 255, 0.05) 0%, rgba(0, 255, 136, 0.05) 100%);
}

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

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

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

.section__header {
    text-align: center;
    margin-bottom: var(--spacing-lg);
}

.section__title {
    font-family: var(--font-secondary);
    font-size: clamp(2rem, 4vw, 3rem);
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
}

.section__subtitle {
    font-size: clamp(1rem, 2vw, 1.25rem);
    color: var(--color-text-muted);
}

/* Grid */
.grid {
    display: grid;
    gap: var(--spacing-md);
}

.grid--2 {
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

.grid--3 {
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

/* Cards */
.card {
    background: var(--color-bg-light);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    transition: var(--transition-base);
}

.card:hover {
    transform: translateY(-8px);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.3);
    border-color: var(--color-primary);
}

.card--feature {
    text-align: center;
}

.card__icon {
    width: 80px;
    height: 80px;
    margin: 0 auto var(--spacing-md);
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-accent) 100%);
    border-radius: 50%;
    font-size: 2rem;
}

.card__title {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

.card__text {
    color: var(--color-text-muted);
    line-height: 1.8;
}

/* Video Section */
.video-container {
    max-width: 900px;
    margin: 0 auto;
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.4);
}

.video-player {
    width: 100%;
    height: auto;
    display: block;
    background: #000;
}

/* YouTube iframe styling */
.video-container iframe {
    width: 100%;
    height: 500px;
    display: block;
    border: none;
    border-radius: var(--radius-lg);
}

@media (max-width: 768px) {
    .video-container iframe {
        height: 300px;
    }
}

/* Tech Grid */
.tech-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: var(--spacing-md);
}

.tech-card {
    background: var(--color-bg-light);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-md);
    transition: var(--transition-base);
}

.tech-card:hover {
    border-color: var(--color-primary);
    transform: translateY(-4px);
}

.tech-card__header {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
}

.tech-card__icon {
    font-size: 2rem;
    color: var(--color-primary);
}

.tech-card__title {
    font-size: 1.75rem;
    font-weight: 700;
}

.tech-card__subtitle {
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-md);
}

.tech-card__list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.tech-card__list li {
    padding-left: var(--spacing-md);
    position: relative;
}

.tech-card__list li::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--color-secondary);
    font-weight: bold;
}

/* SSIRN Section */
.ssirn-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.ssirn-card {
    text-align: center;
    padding: var(--spacing-md);
    background: rgba(0, 102, 255, 0.05);
    border: 2px solid rgba(0, 102, 255, 0.2);
    border-radius: var(--radius-lg);
    transition: var(--transition-base);
}

.ssirn-card:hover {
    border-color: var(--color-primary);
    background: rgba(0, 102, 255, 0.1);
}

.ssirn-card__number {
    font-family: var(--font-secondary);
    font-size: 3rem;
    font-weight: 700;
    color: var(--color-primary);
    margin-bottom: var(--spacing-xs);
}

.ssirn-card__title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
}

.ssirn-card__text {
    color: var(--color-text-muted);
    font-size: 0.9rem;
}

.ssirn-cta {
    text-align: center;
}

/* Timeline */
.timeline {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 50%;
    top: 0;
    bottom: 0;
    width: 2px;
    background: var(--color-border);
    transform: translateX(-50%);
}

.timeline__item {
    position: relative;
    margin-bottom: var(--spacing-lg);
    display: flex;
    align-items: center;
}

.timeline__item:nth-child(odd) {
    flex-direction: row-reverse;
}

.timeline__marker {
    position: absolute;
    left: 50%;
    width: 20px;
    height: 20px;
    background: var(--color-bg-light);
    border: 3px solid var(--color-primary);
    border-radius: 50%;
    transform: translateX(-50%);
    z-index: 2;
}

.timeline__item--active .timeline__marker {
    background: var(--color-primary);
    box-shadow: 0 0 0 8px rgba(0, 102, 255, 0.2);
}

.timeline__content {
    width: 45%;
    padding: var(--spacing-md);
    background: var(--color-bg-light);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    transition: var(--transition-base);
}

.timeline__item:nth-child(odd) .timeline__content {
    text-align: right;
}

.timeline__content:hover {
    border-color: var(--color-primary);
    transform: scale(1.05);
}

.timeline__year {
    color: var(--color-primary);
    font-weight: 700;
    margin-bottom: var(--spacing-xs);
}

.timeline__title {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-xs);
}

.timeline__text {
    color: var(--color-text-muted);
}

.timeline__badge {
    display: inline-block;
    margin-top: var(--spacing-xs);
    padding: 4px 12px;
    background: var(--color-primary);
    border-radius: var(--radius-sm);
    font-size: 0.85rem;
    font-weight: 600;
}

/* Market Cards */
.market-card {
    background: var(--color-bg);
    border: 2px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
    text-align: center;
    transition: var(--transition-base);
}

.market-card:hover {
    border-color: var(--color-primary);
    transform: translateY(-8px);
}

.market-card__icon {
    font-size: 3rem;
    color: var(--color-primary);
    margin-bottom: var(--spacing-md);
}

.market-card__title {
    font-size: 1.5rem;
    margin-bottom: var(--spacing-md);
}

.market-card__value {
    display: flex;
    align-items: baseline;
    justify-content: center;
    gap: var(--spacing-xs);
    margin-bottom: var(--spacing-sm);
}

.market-card__number {
    font-family: var(--font-secondary);
    font-size: 4rem;
    font-weight: 700;
    color: var(--color-primary);
}

.market-card__unit {
    font-size: 1.5rem;
    color: var(--color-text-muted);
}

.market-card__year {
    font-size: 1.25rem;
    color: var(--color-text-muted);
    margin-bottom: var(--spacing-xs);
}

.market-card__growth {
    color: var(--color-secondary);
    font-weight: 600;
}

/* Footer */
.footer {
    background: var(--color-bg-light);
    border-top: 1px solid var(--color-border);
    padding: var(--spacing-xl) 0 var(--spacing-md);
}

.footer__main {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
}

.footer__logo {
    max-width: 200px;
    margin-bottom: var(--spacing-sm);
    background: rgba(255, 255, 255, 0.95);
    padding: 8px 16px;
    border-radius: var(--radius-md);
}

.footer__tagline {
    color: var(--color-text-muted);
    line-height: 1.8;
}

.footer__links {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-md);
}

.footer__title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
}

.footer__list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.footer__list li {
    color: var(--color-text-muted);
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.footer__list a:hover {
    color: var(--color-primary);
}

.footer__bottom {
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--color-border);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
}

.footer__info {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
    color: var(--color-text-muted);
    font-size: 0.9rem;
}

.footer__copyright {
    color: var(--color-text-muted);
    font-size: 0.9rem;
}

/* Back to Top */
.back-to-top {
    position: fixed;
    bottom: var(--spacing-md);
    right: var(--spacing-md);
    width: 50px;
    height: 50px;
    background: var(--color-primary);
    border: none;
    border-radius: 50%;
    color: var(--color-text);
    font-size: 1.25rem;
    cursor: pointer;
    opacity: 0;
    visibility: hidden;
    transition: var(--transition-base);
    z-index: 999;
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
}

.back-to-top:hover {
    background: #0052cc;
    transform: translateY(-4px);
}

/* Responsive Design */
@media (max-width: 1024px) {
    .timeline::before {
        left: 20px;
    }
    
    .timeline__item,
    .timeline__item:nth-child(odd) {
        flex-direction: row;
    }
    
    .timeline__marker {
        left: 20px;
    }
    
    .timeline__content {
        width: calc(100% - 60px);
        margin-left: 60px;
    }
    
    .timeline__item:nth-child(odd) .timeline__content {
        text-align: left;
    }
}

@media (max-width: 768px) {
    .nav__toggle {
        display: block;
    }
    
    .nav__menu {
        position: fixed;
        top: 70px;
        left: -100%;
        width: 100%;
        background: var(--color-bg-light);
        flex-direction: column;
        padding: var(--spacing-md);
        transition: var(--transition-base);
        border-bottom: 1px solid var(--color-border);
    }
    
    .nav__menu.active {
        left: 0;
    }
    
    .nav__list {
        flex-direction: column;
        width: 100%;
        gap: 0;
    }
    
    .nav__link {
        display: block;
        padding: var(--spacing-sm);
        border-bottom: 1px solid var(--color-border);
    }
    
    .nav__logo-img {
        height: 35px;
    }
    
    .hero__cta {
        flex-direction: column;
    }
    
    .footer__main {
        grid-template-columns: 1fr;
    }
    
    .footer__links {
        grid-template-columns: 1fr;
    }
    
    .footer__bottom {
        flex-direction: column;
        text-align: center;
    }
}

@media (max-width: 480px) {
    :root {
        --spacing-xl: 3rem;
        --spacing-lg: 2rem;
    }
    
    .nav__logo-img {
        height: 30px;
    }
    
    .ssirn-card__number {
        font-size: 2.5rem;
    }
    
    .market-card__number {
        font-size: 3rem;
    }
}

/* Image Optimization */
img {
    image-rendering: -webkit-optimize-contrast;
    image-rendering: crisp-edges;
}

/* Lazy Loading */
img[loading="lazy"] {
    opacity: 0;
    transition: opacity 0.3s;
}

img[loading="lazy"].loaded {
    opacity: 1;
}