/* style.css - Design System & Custom Styles for SURD Lab */

/* Import Fonts */
@import url("https://cdn.jsdelivr.net/gh/orioncactus/pretendard@v1.3.9/dist/web/static/pretendard.min.css");
@import url('https://fonts.googleapis.com/css2?family=DM+Sans:ital,opsz,wght@0,9..40,100..1000;1,9..40,100..1000&display=swap');

/* CSS Variables */
:root {
  --primary-color: #3a595b;
  --primary-color-hover: #294042;
  --primary-color-light: #eef2f2;
  --accent-color: #e8c882;
  --accent-color-hover: #d7b56d;
  --accent-color-light: #fefcf7;
  --bg-color: #ffffff;
  --text-color: #1a1a1a;
  --text-secondary: #595959;
  --text-light: #888888;
  --border-color: #eaeaea;
  --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 10px 30px rgba(58, 89, 91, 0.1);
  --font-en: 'DM Sans', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-kr: 'Pretendard', -apple-system, BlinkMacSystemFont, sans-serif;
  --header-height: 76px;
  --max-width: 1200px;
  --transition-fast: 0.2s ease;
  --transition-normal: 0.3s ease;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--header-height);
}

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

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-kr);
  font-weight: 700;
  color: var(--primary-color);
}

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

ul {
  list-style: none;
}

button {
  cursor: pointer;
  border: none;
  background: none;
  font-family: inherit;
}

/* Layout Utilities */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 2rem;
  position: relative;
}

.section {
  padding: 8rem 0;
  border-bottom: 1px solid var(--border-color);
}

.section:last-child {
  border-bottom: none;
}

/* Section Header (Bilingual Format) */
.section-header {
  margin-bottom: 4rem;
}

.section-header h2 {
  font-size: 2.25rem;
  font-weight: 800;
  color: var(--primary-color);
  letter-spacing: -0.03em;
  line-height: 1.2;
}

.section-header .subtitle {
  font-family: var(--font-en);
  font-size: 1rem;
  color: var(--text-light);
  text-transform: uppercase;
  letter-spacing: 0.15em;
  margin-top: 0.5rem;
  font-weight: 500;
  display: block;
}

/* Header & Navigation */
.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: var(--header-height);
  background-color: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border-color);
  z-index: 1000;
  transition: box-shadow var(--transition-fast);
}

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

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

.logo a {
  display: flex;
  align-items: center;
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--primary-color);
  letter-spacing: -0.01em;
}

/* Main Navigation Menu */
.nav-menu {
  display: flex;
  align-items: center;
  height: 100%;
}

.nav-list {
  display: flex;
  flex-direction: row;
  align-items: center;
  gap: 2rem;
  height: 100%;
}

.nav-item {
  position: relative;
  height: 100%;
  display: inline-block;
}

.nav-link {
  font-family: var(--font-en);
  font-size: 0.95rem;
  font-weight: 500;
  padding: 0 1.25rem;
  color: var(--text-secondary);
  height: 100%;
  display: flex;
  align-items: center;
  position: relative;
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: -1px;
  left: 1.25rem;
  right: 1.25rem;
  height: 2px;
  background-color: var(--primary-color);
  transform: scaleX(0);
  transition: transform var(--transition-fast);
}

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

.nav-link.active::after {
  transform: scaleX(1);
}

/* Hover-triggered Dropdown for Navigation Items (like Contact) */
.nav-dropdown {
  position: absolute;
  top: 100%;
  right: 0;
  background-color: var(--bg-color);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  box-shadow: var(--shadow-md);
  padding: 1.25rem;
  width: 280px;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transform: translateY(8px);
  transition: opacity var(--transition-fast), transform var(--transition-fast), visibility var(--transition-fast);
}

.nav-item:hover .nav-dropdown {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  transform: translateY(0);
}

.nav-dropdown-title {
  font-size: 0.8rem;
  text-transform: uppercase;
  color: var(--text-light);
  letter-spacing: 0.05em;
  margin-bottom: 0.5rem;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 0.25rem;
}

.nav-dropdown-info {
  margin-bottom: 0.75rem;
}

.nav-dropdown-info:last-child {
  margin-bottom: 0;
}

.nav-dropdown-label {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--primary-color);
}

.nav-dropdown-value {
  font-size: 0.85rem;
  color: var(--text-secondary);
  word-break: break-all;
}

/* Mobile Hamburger Button */
.hamburger {
  display: none;
  flex-direction: column;
  justify-content: space-between;
  width: 24px;
  height: 18px;
  z-index: 1001;
}

.hamburger span {
  display: block;
  height: 2px;
  width: 100%;
  background-color: var(--primary-color);
  border-radius: 2px;
  transition: transform var(--transition-normal), opacity var(--transition-normal);
}

/* Hero Section */
.hero {
  position: relative;
  min-height: 90vh;
  display: flex;
  align-items: center;
  background-color: #ffffff;
  padding-top: var(--header-height);
  overflow: hidden;
}

/* SVG Mathematical Background Pattern (Surd Concept) */
.hero-bg {
  position: absolute;
  top: 50%;
  right: -5%;
  transform: translateY(-50%);
  width: 55%;
  height: 110%;
  opacity: 0.06;
  color: var(--primary-color);
  pointer-events: none;
  z-index: 1;
}

.hero .container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  align-items: center;
  gap: 4rem;
  width: 100%;
  z-index: 2;
}

.hero-content {
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.hero-subtitle {
  font-family: var(--font-en);
  color: var(--accent-color-hover);
  font-weight: 700;
  font-size: 1.1rem;
  letter-spacing: 0.1em;
  margin-bottom: 1.5rem;
  text-transform: uppercase;
}

.hero-title {
  font-size: 2.85rem;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 2rem;
  letter-spacing: -0.02em;
}

.hero-title span {
  display: block;
  font-size: 1.5rem;
  font-weight: 500;
  color: var(--text-secondary);
  margin-top: 0.5rem;
  letter-spacing: -0.01em;
}

/* Tagline layout - exact 6 lines spacing styled with quote structure */
.hero-tagline {
  font-size: 1.05rem;
  color: var(--text-secondary);
  line-height: 1.8;
  border-left: 3px solid var(--accent-color);
  padding-left: 1.5rem;
  margin-bottom: 2.5rem;
  font-style: normal;
  white-space: pre-line;
}

.hero-buttons {
  display: flex;
  gap: 1rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.85rem 1.75rem;
  font-size: 0.95rem;
  font-weight: 600;
  border-radius: 4px;
  transition: all var(--transition-fast);
}

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

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

.btn-secondary {
  border: 1px solid var(--primary-color);
  color: var(--primary-color);
}

.btn-secondary:hover {
  background-color: var(--primary-color-light);
}

/* Right-side Graphic Illustration for Hero */
.hero-graphic {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
}

.surd-graphic-wrapper {
  position: relative;
  width: 100%;
  max-width: 460px;
  height: 400px;
}

/* Elegant geometric abstract composition */
.geometric-box {
  position: absolute;
  border: 1px solid var(--border-color);
  background: white;
}

.geom-1 {
  width: 80%;
  height: 80%;
  top: 10%;
  left: 10%;
  box-shadow: var(--shadow-lg);
  border-left: 4px solid var(--primary-color);
  display: flex;
  align-items: center;
  justify-content: center;
}

.geom-2 {
  width: 40%;
  height: 40%;
  bottom: 0;
  right: 0;
  border: 2px dashed var(--accent-color);
  background: rgba(232, 200, 130, 0.05);
}

.geom-3 {
  width: 30%;
  height: 30%;
  top: 0;
  left: 0;
  background: var(--primary-color-light);
  border: none;
}

.surd-symbol-styled {
  font-family: var(--font-en);
  font-size: 10rem;
  font-weight: 200;
  color: var(--primary-color);
  position: absolute;
  z-index: 3;
  line-height: 1;
}

/* Statistics Grid */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 2rem;
  background-color: var(--primary-color);
  color: #ffffff;
  padding: 3rem 2rem;
  border-radius: 4px;
  margin-top: -4rem;
  position: relative;
  z-index: 10;
  box-shadow: var(--shadow-lg);
}

.stat-card {
  text-align: center;
  border-right: 1px solid rgba(255, 255, 255, 0.15);
}

.stat-card:last-child {
  border-right: none;
}

.stat-value {
  font-family: var(--font-en);
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--accent-color);
  line-height: 1;
  margin-bottom: 0.5rem;
}

.stat-label-kr {
  font-size: 0.9rem;
  font-weight: 600;
  opacity: 0.95;
}

.stat-label-en {
  font-family: var(--font-en);
  font-size: 0.75rem;
  opacity: 0.6;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-top: 0.15rem;
}

/* Recent News Preview Grid (Home) */
.home-section-split {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4rem;
  margin-top: 5rem;
}

.recent-news-preview h3,
.research-preview-column h3 {
  font-size: 1.5rem;
  margin-bottom: 2rem;
  border-left: 4px solid var(--primary-color);
  padding-left: 1rem;
}

.news-preview-list {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.news-preview-item {
  padding-bottom: 1.25rem;
  border-bottom: 1px solid var(--border-color);
  transition: padding-left var(--transition-fast);
}

.news-preview-item:hover {
  padding-left: 0.5rem;
}

.news-preview-item:last-child {
  border-bottom: none;
}

.news-preview-date {
  font-family: var(--font-en);
  font-size: 0.85rem;
  color: var(--accent-color-hover);
  font-weight: 600;
}

.news-preview-title {
  font-size: 0.95rem;
  font-weight: 700;
  margin: 0.25rem 0;
}

.news-preview-desc {
  font-size: 0.85rem;
  color: var(--text-secondary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.research-preview-list {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.research-preview-item {
  padding: 1.25rem;
  background-color: var(--primary-color-light);
  border-radius: 4px;
  transition: transform var(--transition-fast);
}

.research-preview-item:hover {
  transform: translateX(4px);
}

.research-preview-item h4 {
  font-size: 1.05rem;
  margin-bottom: 0.25rem;
}

.research-preview-item p {
  font-size: 0.85rem;
  color: var(--text-secondary);
}

/* About Section */
.about-grid {
  display: grid;
  grid-template-columns: 1fr 1.2fr;
  gap: 5rem;
  margin-bottom: 6rem;
}

.about-text h3 {
  font-size: 1.5rem;
  margin-bottom: 1.5rem;
}

.about-philosophy {
  font-size: 1.05rem;
  color: var(--text-secondary);
  margin-bottom: 2rem;
  text-align: justify;
}

.pi-welcome-box {
  background-color: var(--primary-color-light);
  padding: 2rem;
  border-left: 4px solid var(--primary-color);
  border-radius: 0 4px 4px 0;
}

.pi-welcome-box p {
  font-size: 0.95rem;
  color: var(--text-color);
  margin-bottom: 1rem;
  line-height: 1.7;
}

.pi-welcome-signature {
  font-weight: 700;
  text-align: right;
  color: var(--primary-color);
}

/* PI Welcome Layout with Profile Photo */
.pi-profile-card {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  border: 1px solid var(--border-color);
  padding: 2.5rem;
  border-radius: 4px;
  background: white;
  box-shadow: var(--shadow-sm);
  height: auto;
}

.pi-avatar-placeholder {
  width: calc(100% + 5rem);
  height: auto;
  margin-top: -2.5rem;
  margin-left: -2.5rem;
  margin-right: -2.5rem;
  border-radius: 4px 4px 0 0;
  background-color: #f0f3f3;
  border: none;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-en);
  font-size: 3rem;
  font-weight: 700;
  color: var(--primary-color);
  margin-bottom: 1.5rem;
  box-shadow: none;
  overflow: hidden;
}

.pi-avatar-placeholder.fallback-active {
  height: 300px;
}

.pi-avatar-placeholder img.avatar-img {
  width: 100%;
  height: auto;
  display: block;
}

.pi-name {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 0.25rem;
}

.pi-role {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
}

.pi-contact-info {
  width: 100%;
  border-top: 1px solid var(--border-color);
  padding-top: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.pi-contact-item {
  display: flex;
  font-size: 0.85rem;
}

.pi-contact-label {
  font-weight: 700;
  width: 80px;
  color: var(--primary-color);
}

.pi-contact-value {
  color: var(--text-secondary);
  flex: 1;
}

/* Lab History Timeline */
.timeline-title-wrap {
  text-align: center;
  margin-bottom: 4rem;
}

.timeline-title-wrap h3 {
  font-size: 1.75rem;
  position: relative;
  display: inline-block;
  padding-bottom: 0.75rem;
}

.timeline-title-wrap h3::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 25%;
  width: 50%;
  height: 2px;
  background-color: var(--accent-color);
}

.timeline-container {
  position: relative;
  max-width: 900px;
  margin: 0 auto;
  padding-left: 2rem;
}

/* Timeline Vertical Line */
.timeline-container::before {
  content: '';
  position: absolute;
  top: 0;
  left: 7px;
  height: 100%;
  width: 2px;
  background-color: var(--border-color);
}

.timeline-item {
  position: relative;
  margin-bottom: 3.5rem;
}

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

/* Timeline node dot */
.timeline-dot {
  position: absolute;
  left: -2rem;
  top: 0.25rem;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background-color: #ffffff;
  border: 4px solid var(--primary-color);
  transition: transform var(--transition-fast), background-color var(--transition-fast);
}

.timeline-item:hover .timeline-dot {
  transform: scale(1.2);
  background-color: var(--accent-color);
}

.timeline-content {
  padding-left: 1rem;
}

.timeline-year {
  font-family: var(--font-en);
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--accent-color-hover);
  margin-bottom: 0.5rem;
}

.timeline-item-title {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

.timeline-item-desc {
  font-size: 0.95rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* Research Section */
.research-areas-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2.5rem;
  margin-bottom: 6rem;
}

/* Research Card with overlay sliding up from bottom (0.3s ease) */
.research-card {
  position: relative;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 3rem 2rem;
  background-color: #ffffff;
  overflow: hidden;
  height: 380px;
  display: flex;
  flex-direction: column;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.research-card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-md);
}

.research-card-icon {
  font-size: 2.5rem;
  color: var(--primary-color);
  margin-bottom: 1.5rem;
}

.research-card h3 {
  font-size: 1.35rem;
  font-weight: 800;
  margin-bottom: 1.25rem;
  line-height: 1.3;
}

.research-card-text {
  font-size: 0.95rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* Sliding Overlay description */
.research-card-overlay {
  position: absolute;
  bottom: -100%;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: var(--primary-color);
  color: #ffffff;
  padding: 3rem 2rem;
  display: flex;
  flex-direction: column;
  justify-content: center;
  transition: bottom 0.3s ease;
  z-index: 5;
}

.research-card:hover .research-card-overlay {
  bottom: 0;
}

.research-card-overlay h4 {
  color: var(--accent-color);
  font-size: 1.25rem;
  margin-bottom: 1rem;
  font-weight: 700;
}

.research-card-overlay p {
  font-size: 0.9rem;
  line-height: 1.7;
  color: rgba(255, 255, 255, 0.9);
}

/* Research Projects List */
.projects-container h3 {
  font-size: 1.5rem;
  margin-bottom: 2rem;
  border-left: 4px solid var(--primary-color);
  padding-left: 1rem;
}

.projects-tabs {
  display: flex;
  gap: 1rem;
  margin-bottom: 2rem;
}

.tab-btn {
  padding: 0.5rem 1.25rem;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
  transition: all var(--transition-fast);
}

.tab-btn:hover {
  background-color: var(--primary-color-light);
  color: var(--primary-color);
}

.tab-btn.active {
  background-color: var(--primary-color);
  color: white;
  border-color: var(--primary-color);
}

.projects-list {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.project-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.5rem;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  background-color: var(--bg-color);
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
}

.project-item:hover {
  transform: translateX(4px);
  box-shadow: var(--shadow-sm);
  border-color: rgba(58, 89, 91, 0.3);
}

.project-main-info {
  flex: 1;
  padding-right: 2rem;
}

.project-status-tag {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.15rem 0.5rem;
  border-radius: 3px;
  margin-bottom: 0.5rem;
  text-transform: uppercase;
}

.project-status-tag.ongoing {
  background-color: var(--accent-color-light);
  color: var(--accent-color-hover);
  border: 1px solid rgba(232, 200, 130, 0.3);
}

.project-status-tag.completed {
  background-color: var(--primary-color-light);
  color: var(--primary-color);
  border: 1px solid rgba(58, 89, 91, 0.15);
}

.project-item-title {
  font-size: 1.1rem;
  font-weight: 700;
  line-height: 1.4;
  margin-bottom: 0.25rem;
}

.project-item-subtitle {
  font-family: var(--font-en);
  font-size: 0.85rem;
  color: var(--text-secondary);
  margin-bottom: 0.5rem;
}

.project-details {
  display: flex;
  gap: 1.5rem;
  font-size: 0.8rem;
  color: var(--text-light);
}

.project-funding strong,
.project-period strong {
  font-weight: 600;
  color: var(--text-secondary);
}

/* Members Section */
.members-category h3 {
  font-size: 1.5rem;
  margin-bottom: 2rem;
  border-left: 4px solid var(--primary-color);
  padding-left: 1rem;
}

.pi-section {
  margin-bottom: 6rem;
}

.student-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2.5rem;
}

.members-section-divider {
  margin: 5rem 0;
  border: 0;
  border-top: 1px solid var(--border-color);
}

/* Member Card with hover reveal details */
.member-card {
  position: relative;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 2.5rem 1.5rem;
  text-align: center;
  background-color: #ffffff;
  overflow: hidden;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  align-items: center;
  transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.member-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-md);
}

/* Initials Avatar Placeholder (Gray box with initials) */
.member-avatar {
  width: 100px;
  height: 100px;
  border-radius: 50%;
  background-color: #f0f2f2;
  color: var(--primary-color);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-en);
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 1.5rem;
  border: 2px solid var(--border-color);
  transition: border-color var(--transition-fast);
  overflow: hidden;
}

.member-avatar img,
.pi-avatar-placeholder img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

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

.member-name {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 0.25rem;
}

.member-name span {
  font-family: var(--font-en);
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-light);
  display: block;
}

.member-role {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent-color-hover);
  margin-bottom: 0.5rem;
}

/* Hover reveal overlay showing research interests + email icon */
.member-hover-overlay {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(58, 89, 91, 0.98);
  color: #ffffff;
  padding: 2rem 1.5rem;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s ease, visibility 0.3s ease;
  z-index: 10;
}

.member-card:hover .member-hover-overlay {
  opacity: 1;
  visibility: visible;
}

.member-hover-title {
  color: var(--accent-color);
  font-size: 0.95rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.2);
  padding-bottom: 0.25rem;
  width: 80%;
  text-transform: uppercase;
}

.member-interests {
  font-size: 0.85rem;
  line-height: 1.5;
  margin-bottom: 0;
  max-width: 90%;
}

/* Publications Section */
.publications-filters {
  display: flex;
  gap: 1rem;
  margin-bottom: 3rem;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 1rem;
}

.filter-btn {
  padding: 0.5rem 1rem;
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--text-secondary);
  position: relative;
  transition: color var(--transition-fast);
}

.filter-btn::after {
  content: '';
  position: absolute;
  bottom: -17px;
  left: 0;
  width: 100%;
  height: 2px;
  background-color: var(--primary-color);
  transform: scaleX(0);
  transition: transform var(--transition-fast);
}

.filter-btn:hover {
  color: var(--primary-color);
}

.filter-btn.active {
  color: var(--primary-color);
}

.filter-btn.active::after {
  transform: scaleX(1);
}

.publications-container-list {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.pub-year-group {
  margin-bottom: 3.5rem;
}

.pub-year-title {
  font-family: var(--font-en);
  font-size: 1.75rem;
  font-weight: 800;
  color: var(--primary-color);
  margin-bottom: 1.5rem;
  border-bottom: 2px solid var(--primary-color-light);
  padding-bottom: 0.5rem;
}

/* Publication Entry with Hover highlights background to #f0f5f5 and shows DOI button */
.pub-item {
  display: flex;
  align-items: flex-start;
  padding: 1.5rem;
  border-bottom: 1px solid var(--border-color);
  background-color: transparent;
  transition: background-color 0.25s ease;
  position: relative;
}

.pub-item:hover {
  background-color: #f0f5f5;
}

.pub-badge {
  font-family: var(--font-en);
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.2rem 0.6rem;
  background-color: var(--primary-color-light);
  color: var(--primary-color);
  border-radius: 3px;
  margin-right: 1.5rem;
  min-width: 80px;
  text-align: center;
  text-transform: uppercase;
  flex-shrink: 0;
  margin-top: 0.25rem;
}

.pub-badge.ssci {
  background-color: #fef8eb;
  color: #c99324;
  border: 1px solid rgba(232, 200, 130, 0.3);
}

.pub-details {
  flex: 1;
  padding-right: 7rem; /* Make room for DOI button sliding in */
}

.pub-title {
  font-size: 1.05rem;
  font-weight: 700;
  line-height: 1.4;
  color: var(--text-color);
  margin-bottom: 0.35rem;
}

.pub-title.kr-title {
  font-family: var(--font-kr);
}

.pub-title-en-sub {
  font-family: var(--font-en);
  font-size: 0.9rem;
  color: var(--text-secondary);
  font-style: italic;
  margin-bottom: 0.35rem;
}

.pub-authors {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-bottom: 0.25rem;
}

.pub-journal {
  font-family: var(--font-en);
  font-size: 0.85rem;
  color: var(--text-light);
}

.pub-journal strong {
  font-weight: 600;
  color: var(--text-secondary);
}

/* DOI Button: slides / fades in on hover */
.pub-doi-btn {
  position: absolute;
  right: 1.5rem;
  top: 50%;
  transform: translateY(-50%) translateX(10px);
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.25s ease, transform 0.25s ease, visibility 0.25s ease;
  z-index: 5;
}

.pub-item:hover .pub-doi-btn {
  opacity: 1;
  visibility: visible;
  transform: translateY(-50%) translateX(0);
}

/* Alumni Section */
.alumni-count-kr {
  font-size: 1.15rem;
  font-weight: 500;
  color: var(--text-color);
  margin-left: 0.4rem;
}

.alumni-count-en {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-light);
  margin-left: 0.3rem;
}

.alumni-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 2rem;
}

.alumni-card {
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 1.75rem 1.25rem;
  background-color: var(--bg-color);
  text-align: center;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.alumni-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-sm);
  border-color: var(--primary-color-light);
}

.alumni-year-badge {
  font-family: var(--font-en);
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--accent-color-hover);
  margin-bottom: 0.5rem;
  display: inline-block;
  letter-spacing: 0.05em;
}

.alumni-name {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
  line-height: 1.3;
}

.alumni-name-en {
  font-family: var(--font-en);
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-light);
  display: block;
  margin-top: 0.2rem;
}

.alumni-degrees {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  width: 100%;
}

.alumni-degree-item {
  font-size: 0.825rem;
  color: var(--text-light);
  line-height: 1.35;
  display: block;
}

/* News Section */
.news-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 2.5rem;
}

/* News card: hover expands description */
.news-card {
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 2rem;
  background-color: #ffffff;
  display: flex;
  flex-direction: column;
  box-shadow: var(--shadow-sm);
  transition: transform var(--transition-normal), box-shadow var(--transition-normal), border-color var(--transition-normal);
}

.news-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent-color);
}

.news-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

.news-date {
  font-family: var(--font-en);
  font-size: 0.85rem;
  color: var(--text-light);
  font-weight: 500;
}

.news-category-badge {
  font-family: var(--font-en);
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.15rem 0.5rem;
  border-radius: 3px;
  text-transform: uppercase;
}

.news-category-badge.award {
  background-color: #fef8eb;
  color: #c99324;
}

.news-category-badge.paper {
  background-color: #eef7f8;
  color: var(--primary-color);
}

.news-category-badge.event {
  background-color: #f5f5f5;
  color: var(--text-secondary);
}

.news-title {
  font-size: 1.15rem;
  font-weight: 800;
  line-height: 1.4;
  color: var(--primary-color);
  margin-bottom: 1rem;
}

/* Hover-triggered description container expansion */
.news-desc-container {
  overflow: hidden;
  max-height: 48px; /* Initially shows ~2 lines of text */
  position: relative;
  transition: max-height 0.4s ease;
}

.news-desc-container::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 20px;
  background: linear-gradient(transparent, #ffffff);
  transition: opacity 0.3s ease;
}

.news-card:hover .news-desc-container {
  max-height: 250px; /* Expands to fit full text */
}

.news-card:hover .news-desc-container::after {
  opacity: 0; /* Fade out the text truncation gradient */
}

.news-desc {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* Contact Section */
.contact-grid {
  display: grid;
  grid-template-columns: 1.1fr 1fr;
  gap: 5rem;
}

.contact-info-block {
  display: flex;
  flex-direction: column;
  gap: 2.5rem;
}

.contact-method h3 {
  font-size: 1.1rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--primary-color);
  margin-bottom: 0.75rem;
  font-weight: 700;
}

.contact-email-link,
.contact-tel-link {
  font-family: var(--font-en);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary-color);
  border-bottom: 2px solid var(--accent-color);
  padding-bottom: 0.25rem;
  display: inline-block;
}

.contact-address-text {
  font-size: 1.05rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.contact-directions {
  background-color: var(--primary-color-light);
  padding: 1.5rem;
  border-radius: 4px;
  font-size: 0.9rem;
  line-height: 1.6;
  color: var(--text-secondary);
  border-left: 3px solid var(--primary-color);
}

/* Maps live embed wrapper styling */
.map-embed-wrapper {
  width: 100%;
  min-height: 380px;
  overflow: hidden;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  box-shadow: var(--shadow-sm);
  background-color: var(--bg-color);
}

.map-embed-wrapper iframe {
  display: block;
  width: 100%;
  height: 380px;
  border: 0;
}

/* Footer Section */
.footer {
  background-color: var(--primary-color);
  color: #ffffff;
  padding: 4rem 0 2rem 0;
  border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.footer-simple {
  padding: 2rem 0;
}

.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.8rem;
  color: rgba(255, 255, 255, 0.6);
}

.footer-credit {
  font-family: var(--font-en);
}

/* Top Scroll Button */
.scroll-top-btn {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 44px;
  height: 44px;
  background-color: var(--primary-color);
  color: white;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-md);
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-fast);
  z-index: 99;
}

.scroll-top-btn.visible {
  opacity: 1;
  visibility: visible;
}

.scroll-top-btn:hover {
  background-color: var(--accent-color-hover);
  color: var(--primary-color);
  transform: translateY(-3px);
}

/* Responsive Media Queries */
@media (max-width: 1024px) {
  .hero .container {
    grid-template-columns: 1fr;
    gap: 3rem;
    text-align: center;
  }
  
  .hero-tagline {
    border-left: none;
    border-top: 3px solid var(--accent-color);
    padding-left: 0;
    padding-top: 1.5rem;
    margin-left: auto;
    margin-right: auto;
    max-width: 600px;
  }
  
  .hero-buttons {
    justify-content: center;
  }
  
  .hero-graphic {
    order: -1;
  }
  
  .surd-graphic-wrapper {
    height: 300px;
  }
  
  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
    margin-top: 2rem;
  }
  
  .stat-card {
    border-right: none;
    padding: 1rem;
  }
  
  .stat-card:nth-child(odd) {
    border-right: 1px solid rgba(255, 255, 255, 0.15);
  }
  
  .about-grid {
    grid-template-columns: 1fr;
    gap: 3rem;
  }
  
  .research-areas-grid {
    grid-template-columns: 1fr;
    gap: 2rem;
  }
  
  .research-card {
    height: auto;
    min-height: 250px;
  }
  
  .research-card-overlay {
    bottom: -100%;
    transition: bottom 0.3s ease;
  }
  
  .student-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .alumni-grid {
    grid-template-columns: repeat(3, 1fr);
  }
  
  .news-grid {
    grid-template-columns: 1fr;
  }
  
  .contact-grid {
    grid-template-columns: 1fr;
    gap: 4rem;
  }
  
  .map-embed-wrapper {
    min-height: 300px;
  }
  .map-embed-wrapper iframe {
    height: 300px;
  }
}

@media (max-width: 768px) {
  :root {
    --header-height: 64px;
  }
  
  .section {
    padding: 5rem 0;
  }
  
  .section-header {
    margin-bottom: 2.5rem;
  }
  
  /* Mobile Navigation */
  .hamburger {
    display: flex;
  }
  
  .nav-list {
    flex-direction: column;
    align-items: flex-start;
    gap: 1.5rem;
    height: auto;
  }
  
  .nav-menu {
    position: fixed;
    top: var(--header-height);
    left: 0;
    width: 100%;
    height: calc(100vh - var(--header-height));
    background-color: var(--bg-color);
    flex-direction: column;
    align-items: flex-start;
    padding: 2rem;
    box-shadow: var(--shadow-md);
    transform: translateX(100%);
    transition: transform var(--transition-normal);
    overflow-y: auto;
  }
  
  .nav-menu.open {
    transform: translateX(0);
  }
  
  .nav-item {
    width: 100%;
    height: auto;
    display: block;
  }
  
  .nav-link {
    width: 100%;
    padding: 1rem 0;
    font-size: 1.2rem;
  }
  
  .nav-link::after {
    display: none;
  }
  
  /* Mobile Nav Dropdown Interaction */
  .nav-dropdown {
    position: static;
    opacity: 1;
    visibility: visible;
    pointer-events: auto;
    box-shadow: none;
    border: none;
    border-left: 2px solid var(--accent-color);
    padding: 0 0 1rem 1rem;
    margin-top: -0.5rem;
    width: 100%;
    transform: none;
    display: none; /* Toggled via JS in mobile */
  }
  
  .nav-item:hover .nav-dropdown {
    transform: none;
  }
  
  .nav-item.dropdown-active .nav-dropdown {
    display: block;
  }
  
  /* Hamburger Open State */
  .hamburger.open span:nth-child(1) {
    transform: translateY(8px) rotate(45deg);
  }
  
  .hamburger.open span:nth-child(2) {
    opacity: 0;
  }
  
  .hamburger.open span:nth-child(3) {
    transform: translateY(-8px) rotate(-45deg);
  }
  
  .hero-title {
    font-size: 2.25rem;
  }
  
  .home-section-split {
    grid-template-columns: 1fr;
    gap: 3rem;
  }
  
  .student-grid {
    grid-template-columns: 1fr;
  }
  
  .pub-item {
    flex-direction: column;
    padding: 1rem 0;
  }
  
  .pub-badge {
    margin-bottom: 0.75rem;
  }
  
  .pub-details {
    padding-right: 0;
  }
  
  .pub-doi-btn {
    position: static;
    transform: none;
    opacity: 1;
    visibility: visible;
    margin-top: 1rem;
    display: inline-block;
  }
  
  .pub-item:hover .pub-doi-btn {
    transform: none;
  }
  
  .alumni-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .footer-bottom {
    flex-direction: column;
    gap: 0.75rem;
    text-align: center;
  }
}

@media (max-width: 480px) {
  .stats-grid {
    grid-template-columns: 1fr;
  }
  
  .stat-card:nth-child(odd) {
    border-right: none;
  }
  
  .alumni-grid {
    grid-template-columns: 1fr;
  }
}

/* =========================================================================
   HOME PAGE SPECIFIC HERO & HEADER OVERRIDES (.home-page)
   ========================================================================= */
:root {
  --hero-overlay-opacity: 0;
  --hero-bg-pos-mobile: 20% center;
}

/* 1. Hero layout top overlap background image */
.home-page .hero {
  position: relative;
  background-image: url('./seoul_dark_40.png');
  background-size: cover;
  background-repeat: no-repeat;
  background-position: center center;
  min-height: 660px;
  display: flex;
  align-items: center;
  padding-top: 0; /* Overrides global padding-top: var(--header-height) */
}

/* Scoped Background Overlay */
.home-page .hero::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 1);
  opacity: var(--hero-overlay-opacity);
  z-index: 1;
  pointer-events: none;
}

/* Scoped Layout container overrides */
.home-page .hero .container {
  grid-template-columns: 1fr;
  width: 100%;
  z-index: 2;
  text-align: left;
}

.home-page .hero-content {
  position: relative;
  z-index: 2;
  max-width: 650px;
  text-align: left;
  padding-top: calc(var(--header-height) + 3rem); /* Prevents overlapping with fixed header */
}

/* Scoped White Typography overrides */
.home-page .hero-title {
  color: #ffffff;
  text-shadow: 0 1px 4px rgba(0, 0, 0, 0.35);
}

.home-page .hero-title span {
  color: rgba(255, 255, 255, 0.94);
  text-shadow: 0 1px 4px rgba(0, 0, 0, 0.35);
}

.home-page .hero-tagline {
  color: rgba(255, 255, 255, 0.92);
  border-left: 3px solid rgba(255, 255, 255, 0.75);
  border-top: none;
  padding-left: 1.5rem;
  padding-top: 0;
  margin-left: 0;
  max-width: 100%;
  text-shadow: 0 1px 4px rgba(0, 0, 0, 0.35);
}

/* 2. Header transition animations */
.home-page .header {
  transition: background-color 0.3s ease, border-color 0.3s ease, box-shadow 0.3s ease, backdrop-filter 0.3s ease, -webkit-backdrop-filter 0.3s ease;
}

.home-page .header .logo a,
.home-page .header .nav-link,
.home-page .header .hamburger span {
  transition: color 0.3s ease, background-color 0.3s ease;
}

/* 3. Transparent header state (not scrolled) */
.home-page .header:not(.scrolled) {
  background-color: transparent;
  backdrop-filter: none;
  -webkit-backdrop-filter: none;
  border-bottom-color: transparent;
  box-shadow: none;
}

.home-page .header:not(.scrolled) .logo a,
.home-page .header:not(.scrolled) .nav-link {
  color: #ffffff;
}

.home-page .header:not(.scrolled) .nav-link::after {
  background-color: #ffffff;
}

.home-page .header:not(.scrolled) .hamburger span {
  background-color: #ffffff;
}

.home-page .header:not(.scrolled) .nav-link:hover {
  color: rgba(255, 255, 255, 0.78);
}

/* Scoped Dropdown Protection (Ensure links keep standard dark colors inside dropdown) */
.home-page .header:not(.scrolled) .nav-dropdown .nav-dropdown-title {
  color: var(--text-light);
}

.home-page .header:not(.scrolled) .nav-dropdown .nav-dropdown-label {
  color: var(--primary-color);
}

.home-page .header:not(.scrolled) .nav-dropdown .nav-dropdown-value {
  color: var(--text-secondary);
}

/* 4. Solid header state (scrolled) */
.home-page .header.scrolled {
  background-color: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border-color);
  box-shadow: var(--shadow-sm);
}

.home-page .header.scrolled .logo a {
  color: var(--primary-color);
}

.home-page .header.scrolled .nav-link {
  color: var(--text-secondary);
}

.home-page .header.scrolled .nav-link:hover,
.home-page .header.scrolled .nav-link.active {
  color: var(--primary-color);
}

.home-page .header.scrolled .hamburger span {
  background-color: var(--primary-color);
}

/* Scoped Mobile responsive tweaks */
@media (max-width: 768px) {
  .home-page .hero {
    min-height: 540px;
    background-position: var(--hero-bg-pos-mobile);
  }
  
  .home-page .hero .container {
    text-align: left;
  }
  
  .home-page .hero-content {
    max-width: 100%;
    padding-top: calc(var(--header-height) + 2rem);
  }

  .home-page .hero-tagline {
    border-left: 3px solid rgba(255, 255, 255, 0.75);
    border-top: none;
    padding-left: 1.25rem;
    padding-top: 0;
    margin-left: 0;
  }

  /* 5. Highly specific mobile drawer color overrides (prevents white-on-white) */
  .home-page .header:not(.scrolled) .nav-menu.open,
  .home-page .header.scrolled .nav-menu.open {
    background-color: var(--bg-color);
  }

  .home-page .header:not(.scrolled) .nav-menu.open .nav-link,
  .home-page .header.scrolled .nav-menu.open .nav-link {
    color: var(--text-secondary);
  }

  .home-page .header:not(.scrolled) .nav-menu.open .nav-link:hover,
  .home-page .header.scrolled .nav-menu.open .nav-link:hover {
    color: var(--primary-color);
  }
}

/* =========================================================================
   NEWS CONTENT TABS & INTERVIEWS STYLING
   ========================================================================= */
.news-content-tabs {
  display: flex;
  justify-content: center;
  gap: 1rem;
  margin-bottom: 3rem;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 1rem;
}

.news-content-tab {
  background: none;
  border: 1px solid var(--border-color);
  padding: 0.6rem 1.75rem;
  font-family: var(--font-en);
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--text-light);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.2s ease;
  letter-spacing: 0.5px;
}

.news-content-tab:hover {
  color: var(--primary-color);
  border-color: var(--primary-color);
}

.news-content-tab.active {
  background-color: var(--primary-color);
  border-color: var(--primary-color);
  color: #ffffff;
}

/* Badges for Interview tab */
.news-category-badge.interview {
  background-color: var(--accent-color);
  color: var(--primary-color);
}

.news-category-badge.column {
  background-color: #f0f5f5;
  color: var(--primary-color);
}

/* Styled empty state inside news content area */
.news-empty-state i {
  animation: bounce 2s infinite;
}

@keyframes bounce {
  0%, 100% {
    transform: translateY(0);
  }
  50% {
    transform: translateY(-5px);
  }
}