/* =========================================
   CSS Custom Properties
   ========================================= */
:root {
  --accent-primary:   #6366f1;
  --accent-secondary: #8b5cf6;
  --accent-light:     rgba(99, 102, 241, 0.12);
  --accent-light-strong: rgba(99, 102, 241, 0.22);

  --bg-base:    #f8f7f4;
  --bg-surface: #ffffff;
  --bg-glass:   rgba(255, 255, 255, 0.70);
  --bg-sidebar: #1e1b4b;

  --text-primary:   #1a1523;
  --text-secondary: #4b4560;
  --text-muted:     #8b829a;
  --text-on-sidebar:     #e0e7ff;
  --text-on-sidebar-dim: rgba(224, 231, 255, 0.60);

  --border-card: rgba(99, 102, 241, 0.18);

  --shadow-card:  0 2px 16px rgba(99, 102, 241, 0.07), 0 1px 3px rgba(0,0,0,0.04);
  --shadow-hover: 0 8px 32px rgba(99, 102, 241, 0.16), 0 2px 8px rgba(0,0,0,0.08);

  --font-heading: 'Space Grotesk', sans-serif;
  --font-body:    'Noto Sans TC', sans-serif;

  --sidebar-width: 260px;
  --content-max:   720px;
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;

  --transition: 250ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 450ms cubic-bezier(0.4, 0, 0.2, 1);

  --timeline-accent: var(--accent-primary);
  --timeline-line:   rgba(99, 102, 241, 0.25);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg-base:    #0f0e17;
    --bg-surface: #1a1830;
    --bg-glass:   rgba(20, 18, 40, 0.78);
    --bg-sidebar: #0c0b14;

    --text-primary:   #ede9fe;
    --text-secondary: #a899c4;
    --text-muted:     #6b5f82;
    --text-on-sidebar:     #c4b5fd;
    --text-on-sidebar-dim: rgba(196, 181, 253, 0.55);

    --border-card: rgba(139, 92, 246, 0.22);

    --shadow-card:  0 2px 16px rgba(0,0,0,0.40), 0 1px 3px rgba(0,0,0,0.30);
    --shadow-hover: 0 8px 32px rgba(99, 102, 241, 0.22), 0 2px 8px rgba(0,0,0,0.40);

    --accent-light:        rgba(99, 102, 241, 0.18);
    --accent-light-strong: rgba(99, 102, 241, 0.30);

    --timeline-line: rgba(139, 92, 246, 0.28);
  }
}

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: var(--font-body);
  font-size: 1rem;
  line-height: 1.7;
  background: var(--bg-base);
  color: var(--text-primary);
  display: flex;
  min-height: 100vh;
}

a { color: var(--accent-primary); text-decoration: none; }
a:hover { text-decoration: underline; }

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

/* =========================================
   Sidebar
   ========================================= */
#sidebar {
  width: var(--sidebar-width);
  min-height: 100vh;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
  overflow-x: hidden;
  background: var(--bg-sidebar);
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 2.5rem 1.5rem 2rem;
  gap: 0;
  flex-shrink: 0;
  z-index: 100;
}

/* Scrollbar for sidebar on overflow */
#sidebar::-webkit-scrollbar { width: 4px; }
#sidebar::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.1); border-radius: 2px; }

.avatar-wrap {
  width: 190px;
  height: 190px;
  border-radius: 50%;
  border: 3px solid rgba(99, 102, 241, 0.5);
  box-shadow: 0 0 0 6px rgba(99, 102, 241, 0.12);
  margin-bottom: 1.1rem;
  flex-shrink: 0;
  perspective: 700px;
  cursor: pointer;
}

.avatar-inner {
  width: 100%;
  height: 100%;
  border-radius: 50%;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.65s cubic-bezier(0.4, 0, 0.2, 1);
}

.avatar-wrap:hover .avatar-inner {
  transform: rotateY(180deg);
}

.avatar-front,
.avatar-back {
  position: absolute;
  width: 100%;
  height: 100%;
  border-radius: 50%;
  overflow: hidden;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
}

.avatar-back {
  transform: rotateY(180deg);
}

.avatar-front img,
.avatar-back img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.sidebar-name {
  font-family: var(--font-heading);
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-on-sidebar);
  text-align: center;
  line-height: 1.3;
  margin-bottom: 0.3rem;
}

.sidebar-title {
  font-size: 0.8rem;
  font-weight: 400;
  color: var(--text-on-sidebar-dim);
  text-align: center;
  margin-bottom: 0.25rem;
  line-height: 1.5;
}

.sidebar-tagline {
  font-size: 0.75rem;
  color: var(--text-on-sidebar-dim);
  text-align: center;
  margin-bottom: 1.75rem;
  font-style: italic;
  min-height: 1.2em;
}

.typed-cursor {
  color: var(--accent-primary);
  font-style: normal;
  opacity: 1;
  animation: typed-blink 0.7s infinite;
}

@keyframes typed-blink {
  0%, 100% { opacity: 1; }
  50%       { opacity: 0; }
}

/* Divider */
.sidebar-divider {
  width: 100%;
  height: 1px;
  background: rgba(255,255,255,0.08);
  margin-bottom: 1.5rem;
}

/* Nav */
.sidebar-nav {
  width: 100%;
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
  margin-bottom: 1.75rem;
}

.sidebar-nav a {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.4rem 0.6rem;
  border-radius: var(--radius-sm);
  font-family: var(--font-heading);
  font-size: 0.82rem;
  font-weight: 500;
  color: var(--text-on-sidebar-dim);
  transition: color var(--transition), background var(--transition), padding-left var(--transition);
  text-decoration: none;
}

.sidebar-nav a:hover,
.sidebar-nav a.active {
  color: var(--text-on-sidebar);
  background: rgba(255,255,255,0.07);
  padding-left: 1rem;
  text-decoration: none;
}

.sidebar-nav a.active::before {
  content: '';
  display: inline-block;
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--accent-primary);
  flex-shrink: 0;
}

/* Social Links */
.social-links {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  width: 100%;
  margin-top: auto;
}

.social-link {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.78rem;
  color: var(--text-on-sidebar-dim);
  transition: color var(--transition);
  text-decoration: none;
  padding: 0.15rem 0;
}

.social-link:hover {
  color: var(--text-on-sidebar);
  text-decoration: none;
}

.social-link svg {
  width: 15px;
  height: 15px;
  flex-shrink: 0;
  fill: currentColor;
}

/* Mobile hamburger (hidden on desktop) */
#mobile-header {
  display: none;
}

/* =========================================
   Main Content
   ========================================= */
#main-content {
  flex: 1;
  min-width: 0;
  padding: 3rem 2.5rem 3rem;
  display: flex;
  flex-direction: column;
  gap: 3.5rem;
}

/* =========================================
   Section
   ========================================= */
.section {
  scroll-margin-top: 1.5rem;
}

.section-title {
  font-family: var(--font-heading);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent-primary);
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--accent-light-strong);
  margin-bottom: 1.75rem;
}

/* =========================================
   Fade-in Animation
   ========================================= */
.fade-in-section {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity var(--transition-slow), transform var(--transition-slow);
}

.fade-in-section.is-visible {
  opacity: 1;
  transform: none;
}

@media (prefers-reduced-motion: reduce) {
  .fade-in-section {
    opacity: 1;
    transform: none;
    transition: none;
  }
}

/* =========================================
   Glass Card
   ========================================= */
.glass-card {
  background: var(--bg-glass);
  backdrop-filter: blur(10px) saturate(1.3);
  -webkit-backdrop-filter: blur(10px) saturate(1.3);
  border: 1px solid var(--border-card);
  border-radius: var(--radius-md);
  padding: 1.5rem 1.75rem;
  box-shadow: var(--shadow-card);
  transition: box-shadow var(--transition-slow), transform var(--transition-slow);
}

.glass-card:hover {
  box-shadow: var(--shadow-hover);
  transform: translateY(-2px);
}

/* =========================================
   About
   ========================================= */
#about .glass-card p {
  color: var(--text-secondary);
  font-size: 0.95rem;
  line-height: 1.85;
}

#about .glass-card p + p {
  margin-top: 0.85rem;
}

#about .glass-card a {
  color: var(--accent-primary);
  text-decoration: underline;
  text-decoration-color: var(--accent-light-strong);
  text-underline-offset: 3px;
}

/* =========================================
   Timeline (Experience)
   modeled after yulunalexliu.github.io
   ========================================= */
#timeline {
  position: relative;
  font-family: var(--font-body);
  padding: 0.5rem 0;
}

/* Central vertical line */
#timeline::before {
  content: '';
  position: absolute;
  left: calc(50% - 2px);
  top: 0;
  bottom: 0;
  width: 4px;
  border-radius: 2px;
  background: linear-gradient(to bottom, var(--accent-primary), var(--accent-secondary));
}

.timelineitem {
  width: 44%;
  position: relative;
  padding: 1rem 1.2rem;
  margin-bottom: 1.75rem;
}

/* Right-side items (odd) */
.timelineitem:nth-child(odd) {
  margin-left: 50%;
  text-align: left;
}

/* Left-side items (even) */
.timelineitem:nth-child(even) {
  margin-right: 50%;
  margin-left: auto;
  text-align: right;
}

/* Dot node */
.timelineitem::before {
  content: '';
  width: 14px;
  height: 14px;
  background: var(--accent-primary);
  border-radius: 50%;
  border: 3px solid var(--bg-base);
  position: absolute;
  top: 1.1rem;
  box-shadow: 0 0 0 3px var(--accent-primary), 0 0 12px rgba(99,102,241,0.35);
}

.timelineitem:nth-child(odd)::before  { left:  -7px; }
.timelineitem:nth-child(even)::before { right: -7px; }

/* Type badge */
.timeline-badge {
  display: inline-block;
  font-family: var(--font-heading);
  font-size: 0.62rem;
  font-weight: 700;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  padding: 2px 8px;
  border-radius: 999px;
  margin-bottom: 0.45rem;
}

.timelineitem[data-type="education"] .timeline-badge {
  background: var(--accent-light);
  color: var(--accent-primary);
}

.timelineitem[data-type="internship"] .timeline-badge {
  background: rgba(139, 92, 246, 0.12);
  color: var(--accent-secondary);
}

/* Institution logo */
.timelineitem img {
  max-height: 52px;
  width: auto;
  object-fit: contain;
  margin: 0.4rem 0;
}

.timelineitem:nth-child(even) img {
  margin-left: auto;
}

/* Date */
.tdate {
  font-family: var(--font-heading);
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--accent-secondary);
  margin-bottom: 0.3rem;
  display: block;
}

/* Title */
.ttitle {
  font-family: var(--font-heading);
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
  margin: 0.25rem 0 0.2rem;
  line-height: 1.35;
}

/* Description lines */
.tdesc {
  font-size: 0.82rem;
  color: var(--text-secondary);
  line-height: 1.55;
}

.tdesc a {
  color: var(--accent-primary);
}

/* Collapsible details */
.tdetails {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

.timelineitem.expanded .tdetails {
  max-height: 600px;
}

.texpand-btn {
  margin-top: 0.5rem;
  background: none;
  border: 1px solid var(--border-card);
  color: var(--accent-primary);
  font-family: var(--font-heading);
  font-size: 0.72rem;
  font-weight: 600;
  padding: 0.2rem 0.75rem;
  border-radius: 999px;
  cursor: pointer;
  transition: background var(--transition), color var(--transition), border-color var(--transition);
}

.texpand-btn:hover {
  background: var(--accent-primary);
  color: #fff;
  border-color: var(--accent-primary);
}

/* =========================================
   News
   ========================================= */
.news-filter {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-bottom: 1.25rem;
}

.filter-btn {
  background: none;
  border: 1.5px solid var(--border-card);
  color: var(--text-muted);
  font-family: var(--font-heading);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  padding: 0.28rem 0.85rem;
  border-radius: 999px;
  cursor: pointer;
  transition: background var(--transition), color var(--transition), border-color var(--transition);
}

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

.filter-btn.active {
  background: var(--accent-primary);
  color: #fff;
  border-color: var(--accent-primary);
}

.news-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.news-item {
  display: flex;
  gap: 1rem;
  align-items: flex-start;
  font-size: 0.88rem;
  padding-bottom: 0.75rem;
  border-bottom: 1px solid var(--accent-light);
}

.news-item:last-child {
  border-bottom: none;
  padding-bottom: 0;
}

.news-date {
  font-family: var(--font-heading);
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--accent-secondary);
  white-space: nowrap;
  padding-top: 0.1rem;
  min-width: 70px;
}

.news-text {
  color: var(--text-secondary);
  line-height: 1.6;
}

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

.btn-show-more {
  margin-top: 1rem;
  background: none;
  border: 1.5px solid var(--border-card);
  color: var(--accent-primary);
  font-family: var(--font-heading);
  font-size: 0.8rem;
  font-weight: 600;
  padding: 0.4rem 1.2rem;
  border-radius: 999px;
  cursor: pointer;
  transition: background var(--transition), color var(--transition);
}

.btn-show-more:hover {
  background: var(--accent-primary);
  color: #fff;
  border-color: var(--accent-primary);
}

/* =========================================
   Publications
   ========================================= */
.pub-list {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.pub-card {
  display: grid;
  grid-template-columns: 110px 1fr;
  gap: 1.25rem;
  align-items: start;
}

.pub-thumb {
  width: 110px;
  height: 80px;
  border-radius: var(--radius-sm);
  overflow: hidden;
  background: var(--accent-light);
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

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

.pub-thumb .thumb-placeholder {
  font-size: 1.8rem;
  color: var(--accent-primary);
  opacity: 0.5;
}

.venue-badge {
  display: inline-block;
  font-family: var(--font-heading);
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  padding: 2px 9px;
  background: var(--accent-light);
  color: var(--accent-primary);
  border-radius: 999px;
  margin-bottom: 0.4rem;
}

.pub-title {
  font-family: var(--font-heading);
  font-size: 0.93rem;
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.4;
  margin-bottom: 0.3rem;
}

.pub-authors {
  font-size: 0.82rem;
  color: var(--text-muted);
  margin-bottom: 0.3rem;
}

.pub-desc {
  font-size: 0.82rem;
  color: var(--text-secondary);
  margin-bottom: 0.6rem;
  line-height: 1.55;
}

/* =========================================
   Projects
   ========================================= */
.project-grid {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.project-card {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 1.25rem;
  align-items: start;
}

.project-img-wrap {
  width: 220px;
  height: 160px;
  border-radius: var(--radius-sm);
  overflow: hidden;
  background: var(--accent-light);
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}

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

.project-img-wrap .img-placeholder {
  font-size: 1.8rem;
  color: var(--accent-primary);
  opacity: 0.4;
}

.project-desc-list {
  margin: 0.3rem 0 0.6rem 1rem;
  padding: 0;
  font-size: 0.82rem;
  color: var(--text-secondary);
  line-height: 1.6;
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
}

.project-title {
  font-family: var(--font-heading);
  font-size: 0.93rem;
  font-weight: 600;
  color: var(--text-primary);
}

.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
}

.tag {
  display: inline-block;
  font-family: var(--font-heading);
  font-size: 0.7rem;
  font-weight: 600;
  padding: 2px 9px;
  background: var(--accent-light);
  color: var(--accent-secondary);
  border-radius: var(--radius-sm);
}

.project-desc {
  font-size: 0.83rem;
  color: var(--text-secondary);
  line-height: 1.6;
  flex: 1;
}

/* =========================================
   Shared: Pill Links
   ========================================= */
.pill-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-top: 0.5rem;
}

.pill-link {
  display: inline-block;
  font-family: var(--font-heading);
  font-size: 0.75rem;
  font-weight: 600;
  padding: 4px 13px;
  border-radius: 999px;
  border: 1.5px solid var(--accent-primary);
  color: var(--accent-primary);
  text-decoration: none;
  transition: background var(--transition), color var(--transition);
}

.pill-link:hover {
  background: var(--accent-primary);
  color: #fff;
  text-decoration: none;
}

/* =========================================
   Teaching
   ========================================= */
.teaching-list {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.teaching-card {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.teaching-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 1rem;
  flex-wrap: wrap;
}

.teaching-course {
  font-family: var(--font-heading);
  font-size: 0.97rem;
  font-weight: 600;
  color: var(--text-primary);
  margin: 0.3rem 0 0.2rem;
}

.teaching-role {
  font-size: 0.82rem;
  color: var(--text-muted);
}

.teaching-role a {
  color: var(--accent-primary);
}

.teaching-note {
  font-size: 0.82rem;
  color: var(--text-secondary);
}

.teaching-labs {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  padding: 0;
  margin: 0;
}

.teaching-labs li {
  display: flex;
  gap: 0.75rem;
  align-items: baseline;
  font-size: 0.82rem;
}

.lab-label {
  font-family: var(--font-heading);
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--accent-primary);
  background: var(--accent-light);
  padding: 2px 8px;
  border-radius: 999px;
  white-space: nowrap;
  flex-shrink: 0;
}

.lab-desc {
  color: var(--text-secondary);
  line-height: 1.55;
}

/* =========================================
   Contact
   ========================================= */
.contact-card {
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.contact-card p {
  font-size: 0.92rem;
  color: var(--text-secondary);
}

.email-link {
  font-family: var(--font-heading);
  font-size: 1rem;
  font-weight: 600;
  color: var(--accent-primary);
  text-decoration: none;
  transition: opacity var(--transition);
}

.email-link:hover { opacity: 0.75; text-decoration: none; }

.contact-note {
  font-size: 0.82rem;
  color: var(--text-muted);
  font-style: italic;
}

/* =========================================
   Footer
   ========================================= */
footer {
  font-size: 0.75rem;
  color: var(--text-muted);
  padding-top: 1rem;
  border-top: 1px solid var(--accent-light);
  margin-top: auto;
}

/* =========================================
   Mobile Responsive
   ========================================= */
@media (max-width: 900px) {
  body {
    flex-direction: column;
  }

  /* Mobile header bar */
  #mobile-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.85rem 1.25rem;
    background: var(--bg-sidebar);
    position: sticky;
    top: 0;
    z-index: 200;
  }

  .mobile-name {
    font-family: var(--font-heading);
    font-size: 1rem;
    font-weight: 700;
    color: var(--text-on-sidebar);
  }

  #burger-btn {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text-on-sidebar);
    padding: 4px;
    display: flex;
    align-items: center;
  }

  #burger-btn svg { width: 22px; height: 22px; fill: none; stroke: currentColor; stroke-width: 2; }

  /* Sidebar becomes a drawer */
  #sidebar {
    position: fixed;
    top: 0;
    left: 0;
    width: 280px;
    height: 100vh;
    z-index: 300;
    transform: translateX(-100%);
    transition: transform var(--transition-slow);
    padding-top: 3.5rem;
  }

  #sidebar.sidebar-open {
    transform: translateX(0);
    box-shadow: 4px 0 30px rgba(0,0,0,0.35);
  }

  /* Overlay behind drawer */
  .sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.45);
    z-index: 250;
  }

  .sidebar-overlay.active { display: block; }

  #main-content {
    padding: 2rem 1.25rem;
    gap: 2.75rem;
  }
}

@media (max-width: 600px) {
  .pub-card {
    grid-template-columns: 1fr;
  }

  .pub-thumb {
    width: 100%;
    height: 140px;
  }

  .project-card {
    grid-template-columns: 120px 1fr;
  }

  .project-img-wrap {
    width: 120px;
    height: 88px;
  }
}

/* Timeline mobile: single-column left-aligned */
@media (max-width: 768px) {
  #timeline::before {
    left: 0;
  }

  .timelineitem {
    width: 100%;
    margin-left: 1.5rem !important;
    margin-right: 0 !important;
    border-left: none !important;
    border-right: none !important;
    text-align: left !important;
    padding: 0.85rem 1rem;
  }

  .timelineitem::before {
    left: -7px !important;
    right: auto !important;
  }

  .timelineitem:nth-child(even) img {
    margin-left: 0;
  }
}