/* ===================================================
   KEETAE YANG 포트폴리오 - CSS Stylesheet

   색상 커스터마이징:
   아래 :root 의 CSS 변수를 수정하면 전체 색상을 변경할 수 있습니다.
   =================================================== */

/* ===== CSS Custom Properties (색상 변수) ===== */
:root {
    /* 메인 컬러 - 언리얼 엔진 느낌의 다크 테마 */
    --color-bg-primary: #0a0a0f;
    --color-bg-secondary: #12121a;
    --color-bg-tertiary: #1a1a28;
    --color-bg-card: #16161f;

    /* 액센트 컬러 */
    --color-accent: #3b82f6;
    --color-accent-hover: #2563eb;
    --color-accent-glow: rgba(59, 130, 246, 0.3);
    --color-accent-subtle: rgba(59, 130, 246, 0.1);

    /* 텍스트 컬러 */
    --color-text-primary: #f1f5f9;
    --color-text-secondary: #94a3b8;
    --color-text-muted: #64748b;

    /* 보더 & 기타 */
    --color-border: rgba(255, 255, 255, 0.08);
    --color-border-hover: rgba(255, 255, 255, 0.15);

    /* 그라디언트 */
    --gradient-accent: linear-gradient(135deg, #3b82f6, #8b5cf6);
    --gradient-card: linear-gradient(135deg, rgba(59, 130, 246, 0.05), rgba(139, 92, 246, 0.05));

    /* 타이포그래피 */
    --font-heading: 'Poppins', sans-serif;
    --font-body: 'Inter', sans-serif;

    /* 사이징 */
    --container-max: 1200px;
    --section-padding: 100px;
    --border-radius: 12px;
    --border-radius-sm: 8px;

    /* 트랜지션 */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
}

/* ===== Reset & Base ===== */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

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

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

ul {
    list-style: none;
}

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

/* ===== Utility Classes ===== */
.container {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 24px;
}

.text-accent {
    color: var(--color-accent);
}

.section {
    padding: var(--section-padding) 0;
    position: relative;
}

.section-title {
    font-family: var(--font-heading);
    font-size: 2.5rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 0.5rem;
    background: var(--gradient-accent);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.section-subtitle {
    text-align: center;
    color: var(--color-text-secondary);
    font-size: 1.1rem;
    margin-bottom: 3rem;
}

/* ===== Buttons ===== */
.btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 14px 28px;
    border-radius: var(--border-radius-sm);
    font-family: var(--font-body);
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-normal);
    border: none;
    position: relative;
    overflow: hidden;
}

.btn-primary {
    background: var(--gradient-accent);
    color: #fff;
    box-shadow: 0 4px 15px var(--color-accent-glow);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px var(--color-accent-glow);
}

.btn-outline {
    background: transparent;
    color: var(--color-text-primary);
    border: 1px solid var(--color-border-hover);
}

.btn-outline:hover {
    border-color: var(--color-accent);
    color: var(--color-accent);
    background: var(--color-accent-subtle);
}

.btn-full {
    width: 100%;
    justify-content: center;
}

.btn-course {
    background: var(--color-bg-tertiary);
    color: var(--color-accent);
    border: 1px solid var(--color-border);
    width: 100%;
    justify-content: center;
}

.btn-course:hover {
    background: var(--color-accent-subtle);
    border-color: var(--color-accent);
}

/* ===== Navigation ===== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 1000;
    padding: 20px 0;
    transition: all var(--transition-normal);
}

.navbar.scrolled {
    background: rgba(10, 10, 15, 0.95);
    backdrop-filter: blur(20px);
    padding: 12px 0;
    border-bottom: 1px solid var(--color-border);
}

.nav-container {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: 8px;
}

/* 로고 이미지 스타일 */
.nav-logo-img {
    height: 32px;
    width: auto;
    object-fit: contain;
}

/* 로고 텍스트 스타일 */
.logo-text {
    font-family: var(--font-heading);
    font-size: 1.2rem;
    font-weight: 700;
    background: var(--gradient-accent);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: 0.5px;
}

.nav-links {
    display: flex;
    align-items: center;
    gap: 32px;
}

.nav-links a {
    font-size: 0.9rem;
    color: var(--color-text-secondary);
    transition: color var(--transition-fast);
    position: relative;
}

.nav-links a:hover {
    color: var(--color-text-primary);
}

.nav-links a.active {
    color: var(--color-accent);
}

.nav-cta {
    padding: 8px 20px !important;
    border: 1px solid var(--color-accent) !important;
    border-radius: var(--border-radius-sm) !important;
    color: var(--color-accent) !important;
}

.nav-cta:hover {
    background: var(--color-accent-subtle) !important;
}

/* Language Toggle */
.lang-toggle {
    display: flex;
    align-items: center;
    gap: 4px;
    background: rgba(255, 255, 255, 0.06);
    border: 1px solid var(--color-border);
    border-radius: 20px;
    padding: 4px 10px;
    cursor: pointer;
    transition: border-color var(--transition-fast), background var(--transition-fast);
    flex-shrink: 0;
}

.lang-toggle:hover {
    border-color: var(--color-border-hover);
    background: rgba(255, 255, 255, 0.10);
}

.lang-option {
    font-family: var(--font-body);
    font-size: 0.75rem;
    font-weight: 600;
    letter-spacing: 0.05em;
    color: var(--color-text-muted);
    transition: color var(--transition-fast);
    cursor: pointer;
    user-select: none;
    padding: 2px 4px;
    border-radius: 12px;
}

.lang-option.active {
    color: var(--color-accent);
}

.lang-divider {
    font-size: 0.7rem;
    color: var(--color-text-muted);
    opacity: 0.5;
    pointer-events: none;
}

/* Mobile Toggle */
.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 5px;
}

.nav-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--color-text-primary);
    transition: all var(--transition-normal);
}

.nav-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
}

.nav-toggle.active span:nth-child(2) {
    opacity: 0;
}

.nav-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
}

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

.hero-bg {
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg, #0a0a1a 0%, #1a1035 40%, #0d1b2a 70%, #0a0a1a 100%);
    background-size: cover;
    background-position: center;
}

#heroCanvas {
    position: absolute;
    inset: 0;
    z-index: 1;
    pointer-events: none;
}

.hero-overlay {
    position: absolute;
    inset: 0;
    background: radial-gradient(ellipse at center, rgba(10, 10, 15, 0.4), rgba(10, 10, 15, 0.85));
    z-index: 2;
    pointer-events: none;
    /* Let clicks pass through to Spline if needed, or to content */
}

.hero-content {
    position: relative;
    z-index: 2;
    max-width: 800px;
    padding: 0 24px;
}

/* UAI 배지 - Hero */
.hero-uai-badge {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    padding: 8px 20px;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid var(--color-accent);
    border-radius: 30px;
    margin-bottom: 1.5rem;
    font-size: 0.85rem;
    color: var(--color-accent);
    font-weight: 500;
}

.uai-badge-img {
    height: 24px;
    width: auto;
    object-fit: contain;
}

.hero-subtitle {
    font-size: 1rem;
    color: var(--color-accent);
    font-weight: 500;
    letter-spacing: 2px;
    text-transform: uppercase;
    margin-bottom: 1rem;
}

.hero-title {
    font-family: var(--font-heading);
    font-size: 3.5rem;
    font-weight: 800;
    line-height: 1.2;
    margin-bottom: 1.5rem;
}

.hero-description {
    font-size: 1.15rem;
    color: var(--color-text-secondary);
    line-height: 1.8;
    margin-bottom: 2rem;
}

.hero-buttons {
    display: flex;
    gap: 16px;
    justify-content: center;
    margin-bottom: 3rem;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 48px;
    padding-top: 2rem;
    border-top: 1px solid var(--color-border);
}

.stat-item {
    text-align: center;
}

.stat-number {
    font-family: var(--font-heading);
    font-size: 2rem;
    font-weight: 700;
    color: var(--color-accent);
}

.stat-suffix {
    font-family: var(--font-heading);
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--color-accent);
}

.stat-label {
    display: block;
    font-size: 0.85rem;
    color: var(--color-text-muted);
    margin-top: 4px;
}

.scroll-indicator {
    position: absolute;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%);
    color: var(--color-text-muted);
    font-size: 1.2rem;
    animation: bounce 2s infinite;
}

@keyframes bounce {

    0%,
    20%,
    50%,
    80%,
    100% {
        transform: translateX(-50%) translateY(0);
    }

    40% {
        transform: translateX(-50%) translateY(-10px);
    }

    60% {
        transform: translateX(-50%) translateY(-5px);
    }
}

/* ===== Fade-up Animation ===== */
.animate-fade-up {
    opacity: 0;
    transform: translateY(30px);
    animation: fadeUp 0.8s ease forwards;
}

.delay-1 {
    animation-delay: 0.2s;
}

.delay-2 {
    animation-delay: 0.4s;
}

.delay-3 {
    animation-delay: 0.6s;
}

.delay-4 {
    animation-delay: 0.8s;
}

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

/* Intersection Observer Animation */
.reveal {
    opacity: 0;
    transform: translateY(40px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

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

/* ===== About Section ===== */
.about-grid {
    display: grid;
    grid-template-columns: 1fr 1.5fr;
    gap: 60px;
    align-items: start;
}

.about-image-wrap {
    position: relative;
}

.about-image {
    width: 100%;
    aspect-ratio: 3/4;
    border-radius: var(--border-radius);
    overflow: hidden;
    border: 1px solid var(--color-border);
}

.profile-img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.about-badge {
    position: absolute;
    bottom: -15px;
    right: -15px;
    background: var(--gradient-accent);
    color: #fff;
    padding: 12px 20px;
    border-radius: var(--border-radius-sm);
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 0.85rem;
    font-weight: 600;
    box-shadow: 0 4px 15px var(--color-accent-glow);
}

.about-badge-img {
    height: 24px;
    width: auto;
    object-fit: contain;
}

.about-content h3 {
    font-family: var(--font-heading);
    font-size: 1.8rem;
    margin-bottom: 1.2rem;
}

.about-content p {
    color: var(--color-text-secondary);
    margin-bottom: 1rem;
    line-height: 1.8;
}

.about-highlights {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    margin-top: 2rem;
}

.highlight-item {
    display: flex;
    align-items: flex-start;
    gap: 12px;
    padding: 16px;
    background: var(--color-bg-card);
    border-radius: var(--border-radius-sm);
    border: 1px solid var(--color-border);
    transition: border-color var(--transition-normal);
}

.highlight-item:hover {
    border-color: var(--color-accent);
}

.highlight-item i {
    color: var(--color-accent);
    font-size: 1.2rem;
    margin-top: 2px;
}

.highlight-item strong {
    display: block;
    font-size: 0.9rem;
    margin-bottom: 2px;
}

.highlight-item span {
    font-size: 0.8rem;
    color: var(--color-text-muted);
}

/* ===== Experience / Timeline ===== */
.experience {
    background: var(--color-bg-secondary);
}

.timeline {
    position: relative;
    max-width: 800px;
    margin: 0 auto;
    padding-left: 50px;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 20px;
    top: 0;
    bottom: 0;
    width: 2px;
    background: var(--color-border);
}

.timeline-item {
    position: relative;
    margin-bottom: 40px;
}

.timeline-marker {
    position: absolute;
    left: -50px;
    top: 0;
    width: 42px;
    height: 42px;
    background: var(--color-bg-card);
    border: 2px solid var(--color-accent);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--color-accent);
    font-size: 0.9rem;
    z-index: 1;
}

.timeline-content {
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius);
    padding: 28px;
    transition: border-color var(--transition-normal);
}

.timeline-content:hover {
    border-color: var(--color-accent);
}

.timeline-badge {
    display: inline-block;
    background: var(--color-accent-subtle);
    color: var(--color-accent);
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 600;
    margin-bottom: 12px;
}

.timeline-content h3 {
    font-family: var(--font-heading);
    font-size: 1.3rem;
    margin-bottom: 4px;
}

.timeline-period {
    color: var(--color-text-muted);
    font-size: 0.9rem;
    margin-bottom: 16px;
}

.timeline-details {
    list-style: none;
    margin-bottom: 16px;
}

.timeline-details li {
    color: var(--color-text-secondary);
    font-size: 0.9rem;
    padding: 4px 0;
    padding-left: 18px;
    position: relative;
}

.timeline-details li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 12px;
    width: 6px;
    height: 6px;
    border-radius: 50%;
    background: var(--color-accent);
}

.timeline-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.timeline-tags span {
    font-size: 0.75rem;
    padding: 4px 10px;
    background: var(--color-bg-tertiary);
    border: 1px solid var(--color-border);
    border-radius: 20px;
    color: var(--color-text-muted);
}

/* ===== Skills Section ===== */
.skills-category {
    margin-bottom: 3rem;
}

.skills-category-title {
    font-family: var(--font-heading);
    font-size: 1.3rem;
    margin-bottom: 1.5rem;
    display: flex;
    align-items: center;
    gap: 10px;
}

.skills-category-title i {
    color: var(--color-accent);
}

.skills-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
}

.skills-grid-5 {
    grid-template-columns: repeat(5, 1fr);
}

.skill-card {
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius);
    padding: 28px 20px;
    text-align: center;
    transition: all var(--transition-normal);
}

.skill-card:hover {
    border-color: var(--color-accent);
    transform: translateY(-4px);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.3);
}

.skill-card.skill-main {
    background: var(--gradient-card);
}

.skill-icon {
    width: 56px;
    height: 56px;
    margin: 0 auto 16px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-accent-subtle);
    border-radius: 14px;
    color: var(--color-accent);
    font-size: 1.4rem;
}

.skill-card h4 {
    font-family: var(--font-heading);
    font-size: 0.95rem;
    margin-bottom: 16px;
}

.skill-bar {
    width: 100%;
    height: 4px;
    background: var(--color-bg-tertiary);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 10px;
}

.skill-bar-fill {
    height: 100%;
    width: 0;
    background: var(--gradient-accent);
    border-radius: 4px;
    transition: width 1.5s ease;
}

.skill-level {
    font-size: 0.75rem;
    color: var(--color-text-muted);
    text-transform: uppercase;
    letter-spacing: 1px;
}

/* ===== Teaching Section ===== */
.teaching {
    background: var(--color-bg-secondary);
}

.teaching-hero {
    text-align: center;
    margin-bottom: 3rem;
}

.teaching-badge-large {
    display: inline-flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
    padding: 30px 50px;
    background: var(--gradient-card);
    border: 1px solid var(--color-accent);
    border-radius: var(--border-radius);
    box-shadow: 0 0 30px var(--color-accent-glow);
}

.teaching-uai-img {
    height: 80px;
    width: auto;
    object-fit: contain;
    margin-bottom: 15px;
}

.teaching-badge-large h3 {
    font-family: var(--font-heading);
    font-size: 1.5rem;
}

.teaching-badge-large p {
    color: var(--color-text-muted);
    font-size: 0.9rem;
}

.teaching-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
    margin-bottom: 3rem;
}

.teaching-card {
    text-align: center;
    padding: 28px 20px;
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius);
    transition: border-color var(--transition-normal);
}

.teaching-card:hover {
    border-color: var(--color-accent);
}

.teaching-icon {
    width: 48px;
    height: 48px;
    margin: 0 auto 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-accent-subtle);
    border-radius: 50%;
    color: var(--color-accent);
    font-size: 1.1rem;
}

.teaching-card h4 {
    font-family: var(--font-heading);
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 4px;
}

.teaching-card p {
    color: var(--color-text-muted);
    font-size: 0.85rem;
}

.teaching-philosophy {
    text-align: center;
    max-width: 700px;
    margin: 0 auto;
}

.teaching-philosophy h3 {
    font-family: var(--font-heading);
    font-size: 1.5rem;
    margin-bottom: 1.5rem;
}

.teaching-philosophy blockquote {
    color: var(--color-text-secondary);
    font-size: 1.05rem;
    line-height: 1.8;
    font-style: italic;
    padding: 24px;
    background: var(--color-bg-card);
    border-left: 3px solid var(--color-accent);
    border-radius: var(--border-radius-sm);
    margin-bottom: 2rem;
}

.philosophy-points {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
    text-align: left;
}

.philosophy-item {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 0.9rem;
    color: var(--color-text-secondary);
}

.philosophy-item i {
    color: var(--color-accent);
}

/* ===== Portfolio Section ===== */
.portfolio {
    background: var(--color-bg-primary);
}

.portfolio-filter {
    display: flex;
    justify-content: center;
    gap: 12px;
    margin-bottom: 2.5rem;
    flex-wrap: wrap;
}

.filter-btn {
    padding: 8px 24px;
    background: transparent;
    border: 1px solid var(--color-border);
    border-radius: 30px;
    color: var(--color-text-secondary);
    font-family: var(--font-body);
    font-size: 0.9rem;
    cursor: pointer;
    transition: all var(--transition-normal);
}

.filter-btn:hover,
.filter-btn.active {
    border-color: var(--color-accent);
    color: var(--color-accent);
    background: var(--color-accent-subtle);
}

.portfolio-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}

.portfolio-item {
    border-radius: var(--border-radius);
    overflow: hidden;
    transition: all var(--transition-normal);
}

.portfolio-item.hidden {
    display: none;
}

.portfolio-thumb {
    position: relative;
    aspect-ratio: 16/10;
    overflow: hidden;
    cursor: pointer;
}

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

.portfolio-thumb:hover .portfolio-img {
    transform: scale(1.05);
}

.portfolio-overlay {
    position: absolute;
    inset: 0;
    background: linear-gradient(to top, rgba(10, 10, 15, 0.95), rgba(10, 10, 15, 0.3));
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    padding: 24px;
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.portfolio-thumb:hover .portfolio-overlay {
    opacity: 1;
}

.portfolio-category {
    display: inline-block;
    font-size: 0.75rem;
    color: var(--color-accent);
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 8px;
}

.portfolio-overlay h4 {
    font-family: var(--font-heading);
    font-size: 1.15rem;
    margin-bottom: 8px;
}

.portfolio-overlay p {
    color: var(--color-text-secondary);
    font-size: 0.85rem;
    margin-bottom: 12px;
}

.portfolio-tags {
    display: flex;
    gap: 6px;
    flex-wrap: wrap;
}

.portfolio-tags span {
    font-size: 0.7rem;
    padding: 3px 8px;
    background: rgba(255, 255, 255, 0.1);
    border-radius: 20px;
    color: var(--color-text-muted);
}

/* ===== Portfolio Modal ===== */
.modal {
    display: none;
    position: fixed;
    inset: 0;
    z-index: 2000;
    align-items: center;
    justify-content: center;
}

.modal.active {
    display: flex;
}

.modal-backdrop {
    position: absolute;
    inset: 0;
    background: rgba(0, 0, 0, 0.85);
    backdrop-filter: blur(10px);
}

.modal-content {
    position: relative;
    max-width: 900px;
    width: 90%;
    max-height: 90vh;
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius);
    overflow: hidden;
    animation: modalIn 0.3s ease;
}

@keyframes modalIn {
    from {
        opacity: 0;
        transform: scale(0.95);
    }

    to {
        opacity: 1;
        transform: scale(1);
    }
}

.modal-close {
    position: absolute;
    top: 16px;
    right: 16px;
    width: 40px;
    height: 40px;
    border: none;
    background: rgba(0, 0, 0, 0.5);
    color: #fff;
    font-size: 1.5rem;
    border-radius: 50%;
    cursor: pointer;
    z-index: 10;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background var(--transition-fast);
}

.modal-close:hover {
    background: rgba(255, 255, 255, 0.2);
}

.modal-image-wrap {
    position: relative;
    width: 100%;
    aspect-ratio: 16/9;
    background: var(--color-bg-primary);
    overflow: hidden;
}

.modal-image {
    width: 100%;
    height: 100%;
    object-fit: contain;
}

.modal-nav {
    position: absolute;
    top: calc(50% + 4px);
    /* 아래로 4px 이동 */
    transform: translateY(-50%);
    width: 44px;
    height: 44px;
    border: none;
    background: rgba(0, 0, 0, 0.5);
    color: #fff;
    font-size: 1.1rem;
    border-radius: 50%;
    cursor: pointer;
    transition: all var(--transition-fast);
    display: none;
    /* Controlled by JS as flex */
    align-items: center;
    justify-content: center;
    padding: 0;
    line-height: 0;
}

.modal-nav:hover {
    background: var(--color-accent);
    transform: translateY(-50%) scale(1.1);
}

.modal-prev {
    left: 20px;
    /* 오른쪽으로 4px 이동 (기본 16px) */
}

.modal-next {
    right: 12px;
    /* 오른쪽으로 4px 이동 (기본 16px) */
}

.modal-info {
    padding: 24px;
}

.modal-category {
    display: inline-block;
    font-size: 0.75rem;
    color: var(--color-accent);
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 8px;
}

.modal-info h3 {
    font-family: var(--font-heading);
    font-size: 1.3rem;
    margin-bottom: 8px;
}

.modal-info p {
    color: var(--color-text-secondary);
    font-size: 0.9rem;
    margin-bottom: 12px;
}

.modal-tags {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
}

.modal-tags span {
    font-size: 0.75rem;
    padding: 4px 10px;
    background: var(--color-bg-tertiary);
    border: 1px solid var(--color-border);
    border-radius: 20px;
    color: var(--color-text-muted);
}

/* ===== Courses Section ===== */
.courses {
    background: var(--color-bg-secondary);
}

.courses-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 30px;
}

.course-card {
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius);
    overflow: hidden;
    transition: all var(--transition-normal);
}

.course-card:hover {
    border-color: var(--color-accent);
    transform: translateY(-4px);
    box-shadow: 0 8px 30px rgba(0, 0, 0, 0.3);
}

.course-thumb {
    position: relative;
    aspect-ratio: 16/9;
    overflow: hidden;
}

.course-thumb-img {
    width: 100%;
    height: 100%;
    object-fit: cover;
}

.course-platform {
    position: absolute;
    top: 12px;
    left: 12px;
}

.course-platform span {
    background: var(--gradient-accent);
    color: #fff;
    padding: 6px 14px;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 600;
}

.course-rank {
    position: absolute;
    top: 12px;
    right: 12px;
    background: rgba(234, 179, 8, 0.9);
    color: #000;
    padding: 6px 14px;
    border-radius: 20px;
    font-size: 0.8rem;
    font-weight: 700;
    display: flex;
    align-items: center;
    gap: 6px;
}

.course-content {
    padding: 24px;
}

.course-content h4 {
    font-family: var(--font-heading);
    font-size: 1.2rem;
    margin-bottom: 12px;
}

.course-content p {
    color: var(--color-text-secondary);
    font-size: 0.9rem;
    line-height: 1.7;
    margin-bottom: 16px;
}

.course-meta {
    display: flex;
    gap: 20px;
    margin-bottom: 12px;
    font-size: 0.85rem;
    color: var(--color-text-muted);
}

.course-meta i {
    color: var(--color-accent);
    margin-right: 6px;
}

.course-highlight {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 14px;
    background: var(--color-accent-subtle);
    border-radius: var(--border-radius-sm);
    font-size: 0.85rem;
    color: var(--color-accent);
    font-weight: 500;
    margin-bottom: 16px;
}

/* ===== Contact Section ===== */
.contact-grid {
    display: grid;
    grid-template-columns: 1fr 1.2fr;
    gap: 60px;
    align-items: start;
}

.contact-info h3 {
    font-family: var(--font-heading);
    font-size: 1.8rem;
    margin-bottom: 1rem;
}

.contact-info>p {
    color: var(--color-text-secondary);
    margin-bottom: 2rem;
    line-height: 1.8;
}

.contact-details {
    margin-bottom: 2rem;
}

.contact-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 0;
    color: var(--color-text-secondary);
}

.contact-item i {
    color: var(--color-accent);
    font-size: 1.1rem;
    width: 20px;
    text-align: center;
}

.contact-item a:hover {
    color: var(--color-accent);
}

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

.social-link {
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: 50%;
    color: var(--color-text-secondary);
    font-size: 1.1rem;
    transition: all var(--transition-normal);
}

.social-link:hover {
    border-color: var(--color-accent);
    color: var(--color-accent);
    background: var(--color-accent-subtle);
    transform: translateY(-2px);
}

/* Contact Form */
.contact-form {
    background: var(--color-bg-card);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius);
    padding: 36px;
}

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

.form-group label {
    display: block;
    font-size: 0.85rem;
    font-weight: 500;
    margin-bottom: 8px;
    color: var(--color-text-secondary);
}

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: 12px 16px;
    background: var(--color-bg-tertiary);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius-sm);
    color: var(--color-text-primary);
    font-family: var(--font-body);
    font-size: 0.9rem;
    transition: border-color var(--transition-fast);
    outline: none;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    border-color: var(--color-accent);
    box-shadow: 0 0 0 3px var(--color-accent-glow);
}

.form-group select {
    cursor: pointer;
    appearance: none;
    -webkit-appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%2394a3b8' d='M6 8L1 3h10z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 16px center;
}

.form-group textarea {
    resize: vertical;
    min-height: 120px;
}

/* ===== Footer ===== */
.footer {
    background: var(--color-bg-secondary);
    border-top: 1px solid var(--color-border);
    padding: 40px 0;
}

.footer-content {
    text-align: center;
}

.footer-logo {
    margin-bottom: 8px;
}

.footer-logo-img {
    height: 32px;
    width: auto;
    object-fit: contain;
    margin-bottom: 8px;
}

.footer-logo-text {
    font-family: var(--font-heading);
    font-size: 1.3rem;
    font-weight: 700;
    background: var(--gradient-accent);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.footer-content>p {
    color: var(--color-text-muted);
    font-size: 0.9rem;
    margin-bottom: 20px;
}

.footer-links {
    display: flex;
    justify-content: center;
    gap: 24px;
    margin-bottom: 20px;
}

.footer-links a {
    color: var(--color-text-secondary);
    font-size: 0.85rem;
    transition: color var(--transition-fast);
}

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

.footer-copy {
    color: var(--color-text-muted);
    font-size: 0.8rem;
}

/* ===== Responsive ===== */
@media (max-width: 1024px) {

    .skills-grid,
    .skills-grid-5 {
        grid-template-columns: repeat(3, 1fr);
    }

    .portfolio-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 768px) {
    :root {
        --section-padding: 60px;
    }

    .nav-links {
        position: fixed;
        top: 0;
        right: -100%;
        width: 280px;
        height: 100vh;
        background: var(--color-bg-secondary);
        border-left: 1px solid var(--color-border);
        flex-direction: column;
        padding: 80px 30px 30px;
        gap: 20px;
        transition: right var(--transition-normal);
    }

    .nav-links.active {
        right: 0;
    }

    .nav-toggle {
        display: flex;
        z-index: 1001;
    }

    .lang-toggle {
        padding: 3px 8px;
    }

    .lang-option {
        font-size: 0.7rem;
    }

    .hero {
        padding-top: 80px;
        align-items: flex-start;
        padding-bottom: 40px;
    }

    .hero-title {
        font-size: 2.2rem;
    }

    .hero-stats {
        flex-direction: column;
        gap: 20px;
    }

    .about-grid {
        grid-template-columns: 1fr;
        gap: 30px;
    }

    .about-image {
        max-width: 300px;
        margin: 0 auto;
    }

    .about-highlights {
        grid-template-columns: 1fr;
    }

    .timeline {
        padding-left: 40px;
    }

    .timeline-marker {
        left: -40px;
        width: 36px;
        height: 36px;
        font-size: 0.8rem;
    }

    .skills-grid,
    .skills-grid-5 {
        grid-template-columns: repeat(2, 1fr);
        gap: 12px;
    }

    .teaching-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .portfolio-grid {
        grid-template-columns: 1fr;
    }

    .courses-grid {
        grid-template-columns: 1fr;
    }

    .contact-grid {
        grid-template-columns: 1fr;
        gap: 40px;
    }

    .section-title {
        font-size: 2rem;
    }

    .philosophy-points {
        grid-template-columns: 1fr;
    }

    .modal-content {
        width: 95%;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 1.8rem;
    }

    .hero-buttons {
        flex-direction: column;
        align-items: center;
    }

    .hero-uai-badge {
        font-size: 0.75rem;
        padding: 6px 14px;
    }

    .skills-grid,
    .skills-grid-5 {
        grid-template-columns: 1fr;
    }

    .teaching-grid {
        grid-template-columns: 1fr;
    }

    .teaching-badge-large {
        padding: 20px 30px;
    }

    .contact-form {
        padding: 24px;
    }
}