/* index.css - 디자인 시스템 및 메인 레이아웃 스타일 */

/* 1. 글로벌 웹 폰트 로드 */
@import url('https://fonts.googleapis.com/css2?family=Outfit:wght@300;400;600;700;800&family=Inter:wght@300;400;500;600;700&family=Noto+Sans+KR:wght@300;400;500;700&display=swap');

/* 2. 디자인 토큰 (CSS variables) */
:root {
  /* 색상 테마: A안 - Royal Gold & Deep Navy (골드 테마 스위칭) */
  --bg-color: #060B19;
  --bg-gradient: radial-gradient(circle at 50% 30%, #0d162d 0%, #060b19 70%);
  --text-primary: #F8FAFC;
  --text-secondary: #94A3B8;
  --text-muted: #64748B;
  
  /* Gold 테마 색상 정의 */
  --primary-gold: #C5A880;
  --primary-gold-rgb: 197, 168, 128;
  --accent-gold: #E5C158;
  --accent-gold-rgb: 229, 193, 88;
  --dark-gold: #9E7D55;
  
  /* 기존 틸 변수명에 골드 변수들을 매핑하여 CSS 전반의 대대적 수정 없이 테마 전환 */
  --primary-teal: var(--primary-gold);
  --primary-teal-rgb: var(--primary-gold-rgb);
  --accent-teal: var(--accent-gold);
  --accent-teal-rgb: var(--accent-gold-rgb);
  --dark-teal: var(--dark-gold);
  
  --card-bg: rgba(15, 23, 42, 0.55);
  --card-border: rgba(255, 255, 255, 0.05);
  --card-hover-border: rgba(var(--accent-teal-rgb), 0.4);
  --glass-blur: blur(16px);
  --shadow-sm: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -4px rgba(0, 0, 0, 0.3);
  --shadow-glow: 0 0 25px rgba(var(--accent-teal-rgb), 0.25);
  
  /* 폰트 및 레이아웃 */
  --font-title: 'Outfit', 'Noto Sans KR', sans-serif;
  --font-body: 'Inter', 'Noto Sans KR', sans-serif;
  --max-width: 1200px;
  --nav-height: 80px;
  --border-radius-sm: 8px;
  --border-radius-md: 16px;
  --border-radius-lg: 24px;
}

/* 세이지 틸 & 딥네이비 테마 (B안) 오버라이드 */
body.theme-teal {
  --bg-color: #080E1E;
  --bg-gradient: radial-gradient(circle at 50% 30%, #0c1836 0%, #080e1e 70%);
  --primary-teal: #00A896;
  --primary-teal-rgb: 0, 168, 150;
  --accent-teal: #02C39A;
  --accent-teal-rgb: 2, 195, 154;
  --dark-teal: #028090;
  --card-border: rgba(255, 255, 255, 0.06);
}

/* 3. 기본 리셋 스타일 */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  scroll-behavior: smooth;
  word-break: keep-all;
  overflow-wrap: break-word;
}

body {
  background-color: var(--bg-color);
  background-image: var(--bg-gradient);
  color: var(--text-primary);
  font-family: var(--font-body);
  line-height: 1.6;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  word-break: keep-all;
  overflow-wrap: break-word;
  transition: background-color 0.4s ease, color 0.3s ease;
}

a {
  color: inherit;
  text-decoration: none;
}

ul {
  list-style: none;
}

/* 4. 공통 유틸리티 클래스 */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  width: 100%;
}

.section {
  padding: 120px 0;
  position: relative;
}

.section-title {
  font-family: var(--font-title);
  font-size: clamp(2rem, 4vw, 2.75rem);
  font-weight: 700;
  margin-bottom: 16px;
  text-align: center;
  letter-spacing: -0.02em;
}

.section-title span {
  background: linear-gradient(135deg, var(--accent-teal), var(--primary-teal));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.section-subtitle {
  color: var(--text-secondary);
  font-size: 1.125rem;
  max-width: 600px;
  margin: 0 auto 64px auto;
  text-align: center;
}

/* 5. 배경 플로팅 기하학 도형 (CSS GPU 가속 적용) */
.bg-decorations {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  overflow: hidden;
  z-index: 1;
}

.decor-shape {
  position: absolute;
  border-radius: 50%;
  filter: blur(100px);
  opacity: 0.15;
  will-change: transform;
}

.shape-1 {
  top: 10%;
  right: 15%;
  width: 350px;
  height: 350px;
  background: var(--primary-teal);
  animation: floatA 16s ease-in-out infinite;
}

.shape-2 {
  top: 40%;
  left: 10%;
  width: 400px;
  height: 400px;
  background: var(--dark-teal);
  animation: floatB 20s ease-in-out infinite;
}

.shape-3 {
  bottom: 15%;
  right: 20%;
  width: 300px;
  height: 300px;
  background: var(--accent-teal);
  animation: floatC 14s ease-in-out infinite;
}

@keyframes floatA {
  0%, 100% { transform: translate(0, 0) scale(1); }
  50%      { transform: translate(30px, -40px) scale(1.1); }
}

@keyframes floatB {
  0%, 100% { transform: translate(0, 0) scale(1); }
  50%      { transform: translate(-25px, 35px) scale(0.95); }
}

@keyframes floatC {
  0%, 100% { transform: translate(0, 0) scale(1); }
  50%      { transform: translate(20px, -20px) scale(1.05); }
}

/* 6. 헤더 및 네비게이션 */
header {
  height: var(--nav-height);
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  z-index: 100;
  background: rgba(8, 14, 30, 0.7);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--card-border);
  transition: all 0.3s ease;
}

header.scrolled {
  background: rgba(8, 14, 30, 0.95);
  box-shadow: var(--shadow-sm);
  height: 70px;
}

.nav-container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 100%;
}

.logo {
  font-family: 'Pretendard', sans-serif;
  font-size: 1.45rem;
  font-weight: 700; /* Pretendard Bold */
  letter-spacing: -0.04em;
  display: inline-flex;
  align-items: center;
  gap: 8px; /* 정렬 및 크기 밸런스 최적화 */
}

.logo .logo-symbol {
  height: 26px;
  width: 26px;
  flex-shrink: 0; /* 찌그러짐 방지 */
  object-fit: contain;
  transition: transform 0.4s cubic-bezier(0.165, 0.84, 0.44, 1);
  filter: drop-shadow(0 2px 6px rgba(var(--primary-teal-rgb), 0.25));
  /* 미세 수직 정렬 보정: 폰트의 한글 베이스라인 특성 보정 */
  transform: translateY(0.5px);
}

.logo:hover .logo-symbol {
  transform: rotate(45deg) scale(1.08) translateY(0.5px);
  filter: drop-shadow(0 4px 10px rgba(var(--accent-teal-rgb), 0.5));
}

.logo span {
  color: var(--text-primary);
}

.logo span strong {
  background: linear-gradient(135deg, var(--accent-teal), var(--primary-teal));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  font-weight: 800; /* Pretendard ExtraBold */
}

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

.nav-link {
  color: var(--text-secondary);
  font-size: 0.95rem;
  font-weight: 500;
  transition: color 0.25s ease;
  position: relative;
}

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

.nav-link::after {
  content: '';
  position: absolute;
  bottom: -6px;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--accent-teal);
  transition: width 0.25s ease;
}

.nav-link:hover::after, .nav-link.active::after {
  width: 100%;
}

.menu-toggle {
  display: none;
  font-size: 1.5rem;
  cursor: pointer;
}

/* 7. Hero Section */
.hero-section {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: var(--nav-height);
  position: relative;
  overflow: hidden;
}

#bg-canvas-container {
  position: fixed;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: 2; /* 배경 데코 도형(1) 위, 텍스트 콘텐츠(10) 아래에 배치 */
  pointer-events: none;
  opacity: 0.32; /* 전체 페이지 배경이므로 눈의 피로를 최소화하기 위해 살짝 투명화 */
  mix-blend-mode: screen;
}

#bg-canvas-container canvas {
  display: block;
  width: 100vw !important;
  height: 100vh !important;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 48px;
  align-items: center;
  position: relative;
  z-index: 10;
}

.hero-content {
  text-align: left;
}

.hero-tag {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  background: rgba(2, 195, 154, 0.1);
  border: 1px solid rgba(2, 195, 154, 0.25);
  border-radius: 50px;
  color: var(--accent-teal);
  font-size: 0.875rem;
  font-weight: 600;
  margin-bottom: 24px;
}

.hero-title {
  font-family: var(--font-title);
  font-size: clamp(1.85rem, 4.5vw, 3.25rem);
  font-weight: 800;
  line-height: 1.35;
  margin-bottom: 28px;
  letter-spacing: -0.03em;
  word-break: keep-all;
  overflow-wrap: break-word;
}

.hero-title span {
  display: block;
}

.hero-title .highlight {
  background: linear-gradient(135deg, #ffffff, var(--accent-teal));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-description {
  color: var(--text-secondary);
  font-size: clamp(1.05rem, 2vw, 1.2rem);
  margin-bottom: 40px;
  line-height: 1.7;
}

.hero-buttons {
  display: flex;
  gap: 16px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 28px;
  border-radius: var(--border-radius-sm);
  font-weight: 600;
  font-size: 1rem;
  transition: all 0.25s ease;
  cursor: pointer;
  gap: 8px;
}

.btn-primary {
  background-color: var(--primary-teal);
  color: var(--text-primary);
  border: 1px solid var(--primary-teal);
  box-shadow: var(--shadow-sm);
}

.btn-primary:hover {
  background-color: var(--accent-teal);
  border-color: var(--accent-teal);
  transform: translateY(-2px);
  box-shadow: var(--shadow-glow);
}

.btn-secondary {
  background-color: transparent;
  color: var(--text-primary);
  border: 1px solid rgba(255, 255, 255, 0.2);
}

.btn-secondary:hover {
  background-color: rgba(255, 255, 255, 0.05);
  border-color: rgba(255, 255, 255, 0.4);
  transform: translateY(-2px);
}

/* 히어로 우측 카드형 프로필 래퍼 */
.hero-visual {
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
}

.hero-profile-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  backdrop-filter: var(--glass-blur);
  padding: 24px;
  border-radius: var(--border-radius-md);
  box-shadow: var(--shadow-lg);
  max-width: 380px;
  width: 100%;
  transition: border-color 0.3s ease;
  will-change: transform;
}

.hero-profile-card:hover {
  border-color: var(--card-hover-border);
}

.profile-img-box {
  width: 100%;
  height: 380px;
  border-radius: var(--border-radius-sm);
  overflow: hidden;
  margin-bottom: 20px;
  border: 1px solid rgba(255, 255, 255, 0.05);
  background-color: rgba(8, 14, 30, 0.3);
}

.profile-img-box img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.5s ease;
}

.hero-profile-card:hover .profile-img-box img {
  transform: scale(1.05);
}

.profile-info h3 {
  font-family: var(--font-title);
  font-size: 1.35rem;
  font-weight: 700;
  margin-bottom: 4px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.profile-info h3 span {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-secondary);
}

.profile-info p {
  color: var(--accent-teal);
  font-size: 0.9rem;
  font-weight: 600;
}

.profile-bullets {
  margin-top: 16px;
  display: flex;
  flex-direction: column;
  gap: 10px;
  list-style: none;
  padding-left: 0;
}

.profile-bullets li {
  font-size: 0.9rem;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 500;
  text-align: left;
}

.profile-bullets li i {
  color: var(--accent-teal);
  font-size: 0.85rem;
  flex-shrink: 0;
  margin-top: 1px;
}

/* 스크롤 다운 가이드 */
.scroll-down {
  position: absolute;
  bottom: 40px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-column: column;
  align-items: center;
  gap: 8px;
  color: var(--text-secondary);
  font-size: 0.8rem;
  font-weight: 500;
  letter-spacing: 0.1em;
  opacity: 0.8;
  z-index: 10;
  pointer-events: none;
}

.scroll-down i {
  font-size: 1.2rem;
  animation: bounce 2s ease-in-out infinite;
}

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50%      { transform: translateY(8px); }
}

/* 8. Biography Section */
.bio-grid {
  display: grid;
  grid-template-columns: 0.9fr 1.1fr;
  gap: 64px;
  align-items: flex-start;
}

.bio-images {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
}

.bio-img-wrapper {
  border-radius: var(--border-radius-sm);
  overflow: hidden;
  height: 280px;
  border: 1px solid var(--card-border);
  background-color: rgba(15, 23, 42, 0.4);
}

.bio-img-wrapper img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.5s ease;
}

.bio-img-wrapper:hover img {
  transform: scale(1.05);
}

.bio-img-span-2 {
  grid-column: span 2;
  height: 300px;
}

.bio-text h3 {
  font-size: 1.75rem;
  font-weight: 700;
  margin-bottom: 24px;
  line-height: 1.4;
}

.bio-text h3 span {
  color: var(--accent-teal);
}

.bio-text p {
  color: var(--text-secondary);
  margin-bottom: 32px;
}

.timeline {
  border-left: 2px solid rgba(2, 195, 154, 0.25);
  padding-left: 24px;
  position: relative;
}

.timeline-item {
  position: relative;
  margin-bottom: 32px;
}

.timeline-item:last-child {
  margin-bottom: 0;
}

.timeline-dot {
  position: absolute;
  left: -31px;
  top: 4px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--bg-color);
  border: 2.5px solid var(--accent-teal);
  box-shadow: 0 0 8px var(--accent-teal);
}

.timeline-time {
  font-family: var(--font-title);
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--accent-teal);
  margin-bottom: 4px;
}

.timeline-title {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 4px;
  color: var(--text-primary);
}

.timeline-desc {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

/* 9. Core Strengths Section (Why Us?) - Accordion UI */
.strengths-accordion {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.accordion-item {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  border-radius: var(--border-radius-md);
  backdrop-filter: var(--glass-blur);
  overflow: hidden;
  transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

.accordion-item:hover {
  border-color: var(--card-hover-border);
}

.accordion-item.active {
  border-color: var(--card-hover-border);
  box-shadow: var(--shadow-glow);
}

.accordion-header {
  padding: 24px 32px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
  user-select: none;
}

.accordion-title-box {
  display: flex;
  align-items: center;
  gap: 20px;
}

.accordion-icon {
  width: 44px;
  height: 44px;
  border-radius: var(--border-radius-sm);
  background: rgba(2, 195, 154, 0.1);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--accent-teal);
  font-size: 1.25rem;
  border: 1px solid rgba(2, 195, 154, 0.15);
  transition: all 0.3s ease;
  flex-shrink: 0;
}

.accordion-item.active .accordion-icon {
  background: var(--primary-teal);
  color: var(--text-primary);
  box-shadow: 0 0 10px rgba(2, 195, 154, 0.3);
}

.accordion-header h3 {
  font-size: 1.2rem;
  font-weight: 700;
  margin: 0;
}

.accordion-arrow {
  color: var(--text-muted);
  transition: transform 0.3s ease;
  font-size: 1.1rem;
}

.accordion-item.active .accordion-arrow {
  transform: rotate(180deg);
  color: var(--accent-teal);
}

.accordion-content {
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows 0.3s cubic-bezier(0.25, 1, 0.5, 1);
  overflow: hidden; /* 접혀있을 때 내용 삐져나옴 방지 */
}

.accordion-item.active .accordion-content {
  grid-template-rows: 1fr;
}

.accordion-content p {
  overflow: hidden;
  padding: 0 32px 24px 96px; /* 아이콘 폭 + 좌우 패딩 감안한 마진 */
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.6;
}

/* 10. Book Highlight Section */
.book-highlight {
  margin-top: 80px;
  background: linear-gradient(135deg, rgba(15, 23, 42, 0.8) 0%, rgba(8, 14, 30, 0.8) 100%);
  border: 1px solid var(--card-border);
  border-radius: var(--border-radius-lg);
  padding: 48px;
  display: grid;
  grid-template-columns: 0.7fr 1.3fr;
  gap: 48px;
  align-items: center;
  box-shadow: var(--shadow-lg);
}

.book-visual {
  display: flex;
  justify-content: center;
  perspective: 1000px;
}

.book-cover {
  width: 200px;
  height: auto;
  border-radius: 4px 12px 12px 4px;
  box-shadow: -10px 15px 30px rgba(0, 0, 0, 0.5);
  transform: rotateY(-15deg) rotateX(5deg);
  transition: transform 0.5s ease;
}

.book-highlight:hover .book-cover {
  transform: rotateY(-5deg) rotateX(2deg) scale(1.03);
}

.book-badge {
  display: inline-block;
  padding: 6px 12px;
  background: linear-gradient(135deg, #D4AF37, #C5A880);
  border-radius: 4px;
  color: #080E1E;
  font-size: 0.8rem;
  font-weight: 700;
  margin-bottom: 16px;
  text-transform: uppercase;
}

.book-title {
  font-size: 2rem;
  font-weight: 800;
  margin-bottom: 8px;
}

.book-subtitle {
  font-family: var(--font-title);
  font-size: 1.125rem;
  color: var(--accent-teal);
  margin-bottom: 20px;
  font-weight: 600;
}

.book-desc {
  color: var(--text-secondary);
  margin-bottom: 24px;
}

.book-stats {
  display: flex;
  gap: 32px;
}

.book-stat-item h4 {
  font-family: var(--font-title);
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--accent-teal);
}

.book-stat-item p {
  color: var(--text-muted);
  font-size: 0.85rem;
}

/* 11. Curriculum Section */
.curriculum-tabs {
  display: flex;
  justify-content: center;
  gap: 16px;
  margin-bottom: 48px;
}

.tab-btn {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  color: var(--text-secondary);
  padding: 14px 28px;
  border-radius: 50px;
  font-weight: 600;
  font-size: 1rem;
  cursor: pointer;
  transition: all 0.25s ease;
  backdrop-filter: var(--glass-blur);
}

.tab-btn:hover {
  border-color: rgba(2, 195, 154, 0.25);
  color: var(--text-primary);
}

.tab-btn.active {
  background: var(--primary-teal);
  border-color: var(--primary-teal);
  color: var(--text-primary);
  box-shadow: 0 0 15px rgba(0, 168, 150, 0.3);
}

.tab-content {
  display: none;
  animation: fadeIn 0.4s ease-in-out forwards;
}

.tab-content.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(15px); }
  to   { opacity: 1; transform: translateY(0); }
}

.curriculum-cards {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 32px;
}

.course-card {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  backdrop-filter: var(--glass-blur);
  padding: 40px;
  border-radius: var(--border-radius-md);
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: border-color 0.3s ease;
}

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

.course-header {
  margin-bottom: 24px;
}

.course-duration {
  font-family: var(--font-title);
  color: var(--accent-teal);
  font-size: 0.9rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.course-title {
  font-size: 1.5rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.course-desc {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

.course-details {
  border-top: 1px solid rgba(255, 255, 255, 0.05);
  padding-top: 24px;
  margin-top: 24px;
}

.detail-item {
  display: flex;
  margin-bottom: 16px;
  align-items: flex-start;
  gap: 12px;
}

.detail-item:last-child {
  margin-bottom: 0;
}

.detail-item i {
  color: var(--accent-teal);
  font-size: 1.1rem;
  margin-top: 2px;
}

.detail-label {
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--text-primary);
  width: 90px;
  flex-shrink: 0;
}

.detail-desc {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

/* 12. References Section */
.metrics-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
  margin-bottom: 80px;
}

.metric-box {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  backdrop-filter: var(--glass-blur);
  padding: 32px 24px;
  border-radius: var(--border-radius-md);
  text-align: center;
}

.metric-num {
  font-family: var(--font-title);
  font-size: 3rem;
  font-weight: 800;
  color: var(--accent-teal);
  margin-bottom: 8px;
  letter-spacing: -0.02em;
}

.metric-label {
  color: var(--text-secondary);
  font-size: 0.95rem;
}

.reference-categories {
  display: flex;
  justify-content: center;
  gap: 16px;
  margin-bottom: 40px;
}

.ref-tab-btn {
  background: transparent;
  border: none;
  color: var(--text-secondary);
  font-weight: 600;
  font-size: 1rem;
  cursor: pointer;
  padding: 8px 16px;
  position: relative;
  transition: color 0.25s ease;
}

.ref-tab-btn.active, .ref-tab-btn:hover {
  color: var(--text-primary);
}

.ref-tab-btn::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 0;
  height: 2px;
  background-color: var(--accent-teal);
  transition: width 0.25s ease;
}

.ref-tab-btn.active::after {
  width: 60%;
}

.logo-grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 16px;
}

.logo-item {
  background: rgba(15, 23, 42, 0.4);
  border: 1px solid var(--card-border);
  height: 100px;
  border-radius: var(--border-radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
  gap: 8px;
  transition: all 0.3s ease;
}

.logo-item:hover {
  border-color: var(--card-hover-border);
  background: var(--card-bg);
  transform: translateY(-4px);
}

.logo-symbol {
  font-size: 1.15rem;
  color: var(--accent-teal);
  opacity: 0.7;
  transition: all 0.3s ease;
}

.logo-item:hover .logo-symbol {
  color: var(--text-primary);
  transform: scale(1.1);
  opacity: 1;
}

.logo-item span {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--text-secondary);
  text-align: center;
  transition: color 0.3s ease;
}

.logo-item:hover span {
  color: var(--text-primary);
}

/* 13. Testimonials Section */
/* 13. Testimonials Section - 3-Card Center-focused Carousel */
.testimonials-slider-container {
  width: 100%;
  max-width: 100%;
  margin: 0 auto;
  position: relative;
  overflow: hidden;
  padding: 40px 0;
  cursor: grab;
  user-select: none;
  -webkit-user-select: none;
}

.testimonials-slider-container.active-drag {
  cursor: grabbing;
}

.testimonials-track {
  display: flex;
  align-items: center;
  transition: transform 0.6s cubic-bezier(0.25, 1, 0.5, 1);
  will-change: transform;
}

.testimonial-card {
  flex: 0 0 620px;
  width: 620px;
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  backdrop-filter: var(--glass-blur);
  padding: 48px;
  border-radius: var(--border-radius-md);
  position: relative;
  margin: 0 20px;
  opacity: 0.45;
  transform: scale(0.9);
  transition: opacity 0.5s cubic-bezier(0.25, 1, 0.5, 1), 
              transform 0.5s cubic-bezier(0.25, 1, 0.5, 1), 
              border-color 0.3s ease;
  will-change: transform, opacity;
}

.testimonial-card.active {
  opacity: 1;
  transform: scale(1.02);
  border-color: var(--card-hover-border);
  box-shadow: var(--shadow-lg);
}

.quote-icon {
  position: absolute;
  top: 32px;
  left: 32px;
  font-size: 4rem;
  color: rgba(2, 195, 154, 0.08);
  pointer-events: none;
}

.testimonial-body {
  font-size: 1.1rem;
  line-height: 1.8;
  margin-bottom: 24px;
  position: relative;
  z-index: 2;
  font-weight: 400;
  color: var(--text-primary);
  word-break: keep-all;
}

.testimonial-author {
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-top: 1px solid rgba(255, 255, 255, 0.05);
  padding-top: 20px;
}

.author-info h4 {
  font-size: 1.05rem;
  font-weight: 700;
}

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

.slider-controls {
  display: flex;
  justify-content: center;
  gap: 16px;
  margin-top: 32px;
}

.ctrl-btn {
  background: var(--card-bg);
  border: 1px solid var(--card-border);
  width: 48px;
  height: 48px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all 0.25s ease;
}

.ctrl-btn:hover {
  border-color: rgba(2, 195, 154, 0.3);
  color: var(--text-primary);
}

/* 14. Contact Section & CTA */
.contact-section {
  position: relative;
  z-index: 10;
}

.cta-box {
  background: linear-gradient(135deg, rgba(15, 23, 42, 0.7) 0%, rgba(8, 14, 30, 0.7) 100%);
  border: 1px solid var(--card-border);
  border-radius: var(--border-radius-lg);
  padding: 64px;
  backdrop-filter: var(--glass-blur);
  text-align: center;
  box-shadow: var(--shadow-lg);
}

.cta-box h3 {
  font-family: var(--font-title);
  font-size: 2.25rem;
  font-weight: 800;
  margin-bottom: 16px;
}

.cta-box p {
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 40px auto;
}

.contact-options {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
  max-width: 900px;
  margin: 0 auto;
}

.contact-card {
  background: rgba(15, 23, 42, 0.4);
  border: 1px solid var(--card-border);
  padding: 24px 16px;
  border-radius: var(--border-radius-md);
  transition: all 0.3s ease;
  display: flex;
  flex-direction: column;
  align-items: center;
  cursor: pointer;
}

.contact-card:hover {
  border-color: var(--card-hover-border);
  background: var(--card-bg);
  transform: translateY(-4px);
}

.contact-card i {
  font-size: 1.75rem;
  color: var(--accent-teal);
  margin-bottom: 16px;
}

.contact-card h4 {
  font-size: 0.95rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.contact-card p {
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: 12px;
  word-break: break-all;
}

.copy-btn {
  background: rgba(2, 195, 154, 0.1);
  border: 1px solid rgba(2, 195, 154, 0.2);
  color: var(--accent-teal);
  padding: 6px 12px;
  font-size: 0.75rem;
  border-radius: 4px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
}

.copy-btn:hover {
  background: var(--primary-teal);
  color: var(--text-primary);
  border-color: var(--primary-teal);
}

/* 15. Footer */
footer {
  border-top: 1px solid var(--card-border);
  padding: 48px 0;
  text-align: center;
  background-color: rgba(8, 14, 30, 0.5);
  color: var(--text-muted);
  font-size: 0.9rem;
}

footer .footer-logo {
  font-family: 'Pretendard', sans-serif;
  font-weight: 700; /* Pretendard Bold */
  letter-spacing: -0.04em;
  color: var(--text-primary);
  font-size: 1.45rem; /* 헤더와 동일하게 통일 */
  margin-bottom: 16px;
  display: flex; /* flex 정렬 적용 */
  align-items: center;
  justify-content: center;
  gap: 8px; /* 헤더와 동일하게 통일 */
}

footer .footer-logo .logo-symbol {
  height: 26px; /* 헤더와 동일하게 통일 (글자 크기의 약 90% 시각 밸런스) */
  width: 26px; /* 헤더와 동일하게 통일 */
  flex-shrink: 0; /* 찌그러짐 방지 */
  object-fit: contain;
  opacity: 0.8;
  transition: opacity 0.3s ease, transform 0.3s ease;
  transform: translateY(0.5px);
}

footer .footer-logo:hover .logo-symbol {
  opacity: 1;
  transform: scale(1.05) translateY(0.5px);
}

footer .footer-logo span {
  color: var(--text-primary);
}

footer .footer-logo span strong {
  color: var(--accent-teal);
  font-weight: 800;
}

/* 16. 반응형 대응 (Media Queries) */
@media (max-width: 1024px) {
  .hero-grid {
    grid-template-columns: 1fr;
    gap: 56px;
    text-align: center;
  }
  
  .hero-content {
    text-align: center;
  }
  
  .hero-buttons {
    justify-content: center;
  }
  
  .bio-grid {
    grid-template-columns: 1fr;
    gap: 48px;
  }
  
  .strengths-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .strength-card-span-2 {
    grid-column: span 1;
  }
  
  .contact-options {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 768px) {
  .nav-links {
    display: none; /* 모바일 메뉴 토글 필요 시 JS 대응 */
  }
  
  .menu-toggle {
    display: block;
  }
  
  .section {
    padding: 80px 0;
  }
  
  .book-highlight {
    grid-template-columns: 1fr;
    padding: 32px 24px;
    text-align: center;
  }
  
  .book-stats {
    justify-content: center;
  }
  
  .curriculum-cards {
    grid-template-columns: 1fr;
  }
  
  .metrics-row {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .logo-grid {
    grid-template-columns: repeat(3, 1fr);
  }
  
  .testimonial-card {
    flex: 0 0 calc(100vw - 80px);
    width: calc(100vw - 80px);
    padding: 32px 24px;
    margin: 0 10px;
  }
}

@media (max-width: 500px) {
  .metrics-row {
    grid-template-columns: 1fr;
  }
  
  .logo-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .contact-options {
    grid-template-columns: 1fr;
  }
  
  .hero-buttons {
    flex-direction: column;
    width: 100%;
  }
  
  .btn {
    width: 100%;
  }
}

/* 17. 테마 전환 토글 버튼 */
.theme-toggle-btn {
  position: fixed;
  bottom: 24px;
  left: 24px;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: rgba(15, 23, 42, 0.7);
  border: 1px solid rgba(var(--accent-teal-rgb), 0.3);
  color: var(--accent-teal);
  font-size: 1.25rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 9999;
  backdrop-filter: blur(12px);
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.3);
  transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.theme-toggle-btn:hover {
  background: rgba(var(--accent-teal-rgb), 0.15);
  border-color: var(--accent-teal);
  transform: scale(1.1) rotate(15deg);
  box-shadow: 0 0 15px rgba(var(--accent-teal-rgb), 0.4);
}

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

/* 모바일 반응형 여백 및 크기 보정 */
@media (max-width: 768px) {
  .theme-toggle-btn {
    bottom: 20px;
    left: 20px;
    width: 44px;
    height: 44px;
    font-size: 1.1rem;
  }
}

/* 데스크탑 뷰포트에서 5대 강점 아코디언 상시 전개 및 정렬 보정 */
@media (min-width: 1024px) {
  .strengths-accordion .accordion-item {
    cursor: default;
  }
  .strengths-accordion .accordion-item .accordion-arrow {
    display: none; /* 토글 화살표 숨김 */
  }
  .strengths-accordion .accordion-item .accordion-content {
    grid-template-rows: 1fr !important; /* 상시 펼침 */
    opacity: 1 !important;
    overflow: visible !important;
  }
  .strengths-accordion .accordion-item:hover {
    border-color: var(--card-hover-border);
    box-shadow: var(--shadow-glow);
  }
  .strengths-accordion .accordion-item .accordion-icon {
    background: var(--primary-teal);
    color: var(--text-primary);
    box-shadow: 0 0 10px rgba(var(--primary-teal-rgb), 0.3);
  }
}