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

:root {
  --navy: #1a3a2a;
  --navy-light: #2a5a40;
  --accent: #2d7a4f;
  --accent-hover: #1d6a3f;
  --text: #2c2c2c;
  --text-light: #555;
  --text-muted: #777;
  --bg: #fdfdfd;
  --bg-alt: #f3f7f5;
  --border: #d4e0d9;
  --link: #2a6b45;
  --link-hover: #1a4d32;
  --sidebar-width: 260px;
  --content-max: 720px;
  --page-max: 1060px;
}

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

body {
  font-family: 'Source Sans 3', 'Segoe UI', sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

a {
  color: var(--link);
  text-decoration: none;
  transition: color 0.2s ease;
}

a:hover {
  color: var(--link-hover);
  text-decoration: underline;
}

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

/* ====== NAVIGATION ====== */
nav.topnav {
  background: var(--navy);
  padding: 0 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 2px 8px rgba(0,0,0,0.12);
}

nav.topnav .brand {
  font-family: 'Libre Baskerville', Georgia, serif;
  font-size: 1.2rem;
  color: #fff;
  font-weight: 700;
  letter-spacing: 0.02em;
}

nav.topnav .brand:hover {
  color: #d4e8dc;
  text-decoration: none;
}

nav.topnav ul {
  list-style: none;
  display: flex;
  gap: 0.25rem;
}

nav.topnav ul li a {
  color: #ccd6e6;
  padding: 0.5rem 0.9rem;
  border-radius: 4px;
  font-size: 0.92rem;
  font-weight: 500;
  transition: background 0.2s, color 0.2s;
}

nav.topnav ul li a:hover,
nav.topnav ul li a.active {
  background: rgba(255,255,255,0.1);
  color: #fff;
  text-decoration: none;
}

.hamburger {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.hamburger span {
  display: block;
  width: 22px;
  height: 2px;
  background: #ccd6e6;
  margin: 5px 0;
  border-radius: 2px;
  transition: 0.3s;
}

/* ====== MAIN LAYOUT ====== */
.page-wrapper {
  max-width: var(--page-max);
  margin: 0 auto;
  padding: 2.5rem 2rem 4rem;
  display: flex;
  gap: 3rem;
}

/* ====== SIDEBAR (home page) ====== */
.sidebar {
  width: var(--sidebar-width);
  flex-shrink: 0;
  text-align: center;
}

.sidebar .profile-photo {
  width: 200px;
  height: 267px;
  border-radius: 6px;
  object-fit: cover;
  margin: 0 auto 1rem;
  border: 3px solid var(--border);
  background: var(--bg-alt);
}

.sidebar .quick-links {
  font-size: 0.88rem;
  margin-bottom: 1.2rem;
  color: var(--text-muted);
}

.sidebar .quick-links a {
  font-weight: 600;
  cursor: pointer;
}

.sidebar .quick-links span {
  margin: 0 0.3rem;
  color: var(--border);
}

.sidebar .name {
  font-family: 'Libre Baskerville', Georgia, serif;
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--navy);
  margin-bottom: 0.3rem;
}

.sidebar .title-line {
  font-size: 0.92rem;
  color: var(--text-light);
  margin-bottom: 0.15rem;
  font-weight: 500;
}

.sidebar .email-link {
  font-size: 0.85rem;
  color: var(--accent);
  margin-top: 0.5rem;
  display: block;
}

/* ====== MAIN CONTENT ====== */
.main-content {
  flex: 1;
  max-width: var(--content-max);
  min-width: 0;
}

.bio-text {
  font-size: 1rem;
  line-height: 1.8;
  margin-bottom: 1rem;
  color: var(--text);
}

.cv-link {
  font-size: 0.9rem;
  font-weight: 600;
  color: var(--accent);
}

/* ====== SECTION HEADINGS ====== */
.section-heading {
  font-family: 'Libre Baskerville', Georgia, serif;
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--navy);
  margin: 2.2rem 0 1rem;
  padding-bottom: 0.4rem;
  border-bottom: 2px solid var(--border);
}

/* ====== PAPER LIST ====== */
.paper-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 1.2rem;
}

.paper-list li {
  font-size: 0.95rem;
  line-height: 1.6;
  padding-left: 1rem;
  position: relative;
}

.paper-list li::before {
  content: '•';
  position: absolute;
  left: 0;
  color: var(--accent);
  font-weight: bold;
}

.paper-list li .paper-title {
  font-weight: 700;
  color: var(--link);
}

.paper-list li .paper-title:hover {
  color: var(--link-hover);
}

.paper-list li .coauthors {
  color: var(--text-light);
}

.paper-list li .paper-detail {
  font-size: 0.88rem;
  color: var(--text-muted);
  font-style: italic;
  margin-top: 0.2rem;
}

/* ====== ABSTRACT TOGGLE ====== */
.abstract-toggle {
  display: inline-block;
  font-size: 0.84rem;
  font-weight: 600;
  color: var(--accent);
  cursor: pointer;
  margin-top: 0.3rem;
  padding: 0.15rem 0.5rem;
  border: 1px solid var(--accent);
  border-radius: 3px;
  background: transparent;
  transition: background 0.2s, color 0.2s;
  user-select: none;
}

.abstract-toggle:hover {
  background: var(--accent);
  color: #fff;
}

.abstract-content {
  display: none;
  margin-top: 0.6rem;
  padding: 0.8rem 1rem;
  background: var(--bg-alt);
  border-left: 3px solid var(--accent);
  border-radius: 0 4px 4px 0;
  font-size: 0.88rem;
  line-height: 1.7;
  color: var(--text-light);
}

.abstract-content.open {
  display: block;
}

.presentations {
  font-size: 0.86rem;
  color: var(--text-muted);
  margin-top: 0.4rem;
}

/* ====== NEWS LIST ====== */
.news-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.news-list li a {
  font-size: 0.9rem;
  line-height: 1.5;
  color: var(--text-light);
  display: block;
  padding: 0.4rem 0;
  border-bottom: 1px solid var(--bg-alt);
  transition: color 0.2s;
}

.news-list li a:hover {
  color: var(--link);
  text-decoration: none;
}

/* ====== FULL WIDTH PAGE ====== */
.page-full {
  max-width: var(--page-max);
  margin: 0 auto;
  padding: 2.5rem 2rem 4rem;
}

.page-title {
  font-family: 'Libre Baskerville', Georgia, serif;
  font-size: 1.6rem;
  font-weight: 700;
  color: var(--navy);
  margin-bottom: 1.5rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--border);
}

.page-full p,
.page-full li {
  font-size: 0.97rem;
  line-height: 1.8;
  color: var(--text);
}

.page-full p + p {
  margin-top: 1rem;
}

/* ====== TABLE ====== */
.info-table {
  width: 100%;
  border-collapse: collapse;
  margin: 1rem 0 2rem;
}

.info-table th,
.info-table td {
  text-align: left;
  padding: 0.6rem 1rem;
  font-size: 0.93rem;
  border-bottom: 1px solid var(--border);
}

.info-table th {
  font-weight: 700;
  color: var(--navy);
  background: var(--bg-alt);
  white-space: nowrap;
}

.info-table td {
  color: var(--text);
}

/* ====== EXPERIENCE ====== */
.experience-item {
  margin-bottom: 2rem;
}

.experience-item .exp-header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  flex-wrap: wrap;
  margin-bottom: 0.3rem;
}

.experience-item .exp-company {
  font-family: 'Libre Baskerville', Georgia, serif;
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--navy);
}

.experience-item .exp-date {
  font-size: 0.88rem;
  color: var(--text-muted);
}

.experience-item .exp-role {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-light);
  margin-bottom: 0.2rem;
}

.experience-item .exp-location {
  font-size: 0.88rem;
  color: var(--text-muted);
  margin-bottom: 0.6rem;
}

.experience-item ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.experience-item ul li {
  font-size: 0.93rem;
  line-height: 1.7;
  padding-left: 1rem;
  position: relative;
  color: var(--text);
}

.experience-item ul li::before {
  content: '•';
  position: absolute;
  left: 0;
  color: var(--accent);
  font-weight: bold;
}

/* ====== CONTACT PAGE ====== */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2rem;
  margin-top: 1rem;
}

.contact-card {
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 1.5rem;
}

.contact-card h3 {
  font-family: 'Libre Baskerville', Georgia, serif;
  font-size: 1rem;
  color: var(--navy);
  margin-bottom: 0.8rem;
}

.contact-card p {
  font-size: 0.93rem;
  line-height: 1.7;
  color: var(--text-light);
}

.contact-card .wechat-qr {
  max-width: 180px;
  margin-top: 0.5rem;
  border-radius: 4px;
  border: 1px solid var(--border);
}

/* ====== WECHAT POPUP (sidebar) ====== */
.wechat-overlay {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,0.5);
  z-index: 200;
  justify-content: center;
  align-items: center;
}

.wechat-overlay.open {
  display: flex;
}

.wechat-popup {
  background: #fff;
  border-radius: 8px;
  padding: 2rem;
  text-align: center;
  max-width: 300px;
  box-shadow: 0 8px 32px rgba(0,0,0,0.2);
  position: relative;
}

.wechat-popup h3 {
  font-family: 'Libre Baskerville', Georgia, serif;
  font-size: 1rem;
  color: var(--navy);
  margin-bottom: 0.5rem;
}

.wechat-popup p {
  font-size: 0.88rem;
  color: var(--text-muted);
  margin-bottom: 1rem;
}

.wechat-popup img {
  max-width: 200px;
  margin: 0 auto;
  border-radius: 4px;
  border: 1px solid var(--border);
}

.wechat-popup .close-btn {
  position: absolute;
  top: 0.5rem;
  right: 0.8rem;
  font-size: 1.3rem;
  background: none;
  border: none;
  cursor: pointer;
  color: var(--text-muted);
  line-height: 1;
}

.wechat-popup .close-btn:hover {
  color: var(--text);
}

/* ====== FOOTER ====== */
footer {
  text-align: center;
  padding: 1.5rem 2rem;
  font-size: 0.85rem;
  color: var(--text-muted);
  border-top: 1px solid var(--border);
  max-width: var(--page-max);
  margin: 0 auto;
}

footer a {
  color: var(--text-muted);
  margin: 0 0.5rem;
}

footer a:hover {
  color: var(--link);
}

/* ====== RESPONSIVE ====== */
@media (max-width: 768px) {
  nav.topnav {
    padding: 0 1rem;
  }

  nav.topnav ul {
    display: none;
    position: absolute;
    top: 56px;
    left: 0;
    right: 0;
    background: var(--navy);
    flex-direction: column;
    padding: 0.5rem 0;
    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
  }

  nav.topnav ul.open {
    display: flex;
  }

  nav.topnav ul li a {
    padding: 0.7rem 1.5rem;
    display: block;
  }

  .hamburger {
    display: block;
  }

  .page-wrapper {
    flex-direction: column;
    padding: 1.5rem 1rem 3rem;
    gap: 2rem;
  }

  .sidebar {
    width: 100%;
  }

  .sidebar .profile-photo {
    width: 160px;
    height: 213px;
  }

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

  .page-full {
    padding: 1.5rem 1rem 3rem;
  }

  .experience-item .exp-header {
    flex-direction: column;
  }
}