/* ============================================================
   AI4Science Lab Website - Hainan Normal University
   ============================================================ */
:root {
  --color-primary: #2b7de9;
  --color-primary-dark: #1a5cb0;
  --color-primary-light: #5a9dee;
  --color-accent: #0ca678;
  --color-accent-hover: #099268;
  --color-bg: #f5f7fa;
  --color-white: #ffffff;
  --color-text: #222831;
  --color-text-light: #5f6b7a;
  --color-border: #dde2e7;
  --color-success: #27ae60;
  --color-info: #3498db;
  --font-sans: "Segoe UI", "PingFang SC", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
  --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --transition: 0.2s ease;
  --max-width: 1200px;
}

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

body {
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

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

a {
  color: var(--color-primary-light);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover {
  color: var(--color-primary-dark);
}

ul {
  list-style: none;
}

.skip-link {
  position: absolute;
  top: -100px;
  left: 0;
  background: var(--color-primary);
  color: #fff;
  padding: 8px 16px;
  z-index: 1000;
  font-weight: 600;
}

.skip-link:focus {
  top: 0;
}

.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

.site-header {
  background: var(--color-white);
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: 0;
  z-index: 100;
}

.site-header > .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 68px;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.35rem;
  font-weight: 700;
  color: var(--color-primary-dark);
  text-decoration: none;
}

.logo-icon {
  font-size: 1.6rem;
}

.logo-text {
  letter-spacing: -0.5px;
}

.nav-desktop {
  display: flex;
  align-items: center;
  gap: 6px;
}

.nav-desktop a {
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  color: var(--color-text);
  font-weight: 500;
  font-size: 0.95rem;
  transition: background var(--transition), color var(--transition);
}

.nav-desktop a:hover,
.nav-desktop a.active {
  background: var(--color-primary);
  color: #fff;
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
}

.nav-toggle span {
  display: block;
  width: 26px;
  height: 3px;
  background: var(--color-primary);
  border-radius: 3px;
  transition: transform var(--transition);
}

.nav-mobile {
  display: none;
  background: var(--color-white);
  border-top: 1px solid var(--color-border);
  padding: 8px 20px 16px;
}

.nav-mobile[aria-hidden="false"] {
  display: block;
}

.nav-mobile a {
  display: block;
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  color: var(--color-text);
  font-weight: 500;
  font-size: 1.05rem;
  transition: background var(--transition);
}

.nav-mobile a:hover {
  background: var(--color-bg);
  color: var(--color-primary);
}

main {
  min-height: 60vh;
}

.section {
  padding: 60px 0;
}

.section-alt {
  background: var(--color-white);
}

.section-title {
  font-size: 2rem;
  font-weight: 700;
  color: var(--color-primary-dark);
  margin-bottom: 12px;
}

.section-subtitle {
  font-size: 1.15rem;
  color: var(--color-text-light);
  margin-bottom: 36px;
  max-width: 700px;
}

.section-divider {
  width: 60px;
  height: 4px;
  background: var(--color-accent);
  border-radius: 2px;
  margin-bottom: 32px;
}

/* ===== Hero Section (Redesigned) ===== */
.hero {
  background:
    linear-gradient(160deg, #eef2ff 0%, #e0f2f1 40%, #f5f7fa 100%);
  color: var(--color-text);
  padding: 100px 0 80px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  top: -80px;
  right: -120px;
  width: 500px;
  height: 500px;
  background: radial-gradient(circle, rgba(43,125,233,0.08) 0%, transparent 70%);
  border-radius: 50%;
  pointer-events: none;
}

.hero::after {
  content: "";
  position: absolute;
  bottom: -100px;
  left: -100px;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, rgba(12,166,120,0.07) 0%, transparent 70%);
  border-radius: 50%;
  pointer-events: none;
}

.hero .container {
  position: relative;
  z-index: 1;
}

.hero-badge {
  display: inline-block;
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  color: #fff;
  padding: 6px 20px;
  border-radius: 30px;
  font-size: 0.85rem;
  font-weight: 600;
  margin-bottom: 24px;
  letter-spacing: 0.5px;
}

.hero h1 {
  font-size: 3rem;
  font-weight: 800;
  margin-bottom: 20px;
  background: linear-gradient(135deg, var(--color-primary-dark), var(--color-accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1.3;
}

.hero h1 .highlight {
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 1.15rem;
  color: var(--color-text-light);
  max-width: 650px;
  margin: 0 auto 36px;
  line-height: 1.9;
}

.hero-stats {
  display: flex;
  justify-content: center;
  gap: 48px;
  margin-bottom: 36px;
  flex-wrap: wrap;
}

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

.hero-stat .stat-num {
  display: block;
  font-size: 2rem;
  font-weight: 800;
  color: var(--color-primary);
  line-height: 1;
}

.hero-stat .stat-label {
  display: block;
  font-size: 0.85rem;
  color: var(--color-text-light);
  margin-top: 6px;
}

.hero-actions {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

.hero-actions .btn-outline {
  background: transparent;
  border: 2px solid var(--color-primary);
  color: var(--color-primary);
}

.hero-actions .btn-outline:hover {
  background: var(--color-primary);
  color: #fff;
}

/* ===== Buttons ===== */
.btn {
  display: inline-block;
  padding: 12px 28px;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: 1rem;
  text-align: center;
  transition: all var(--transition);
  cursor: pointer;
  border: none;
  text-decoration: none;
}

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

.btn-primary:hover {
  background: var(--color-primary-dark);
  color: #fff;
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn-outline {
  background: transparent;
  border: 2px solid var(--color-primary);
  color: var(--color-primary);
}

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

/* dark variant for non-hero pages */
.btn-outline-dark {
  background: transparent;
  border: 2px solid var(--color-primary);
  color: var(--color-primary);
}

.btn-outline-dark:hover {
  background: var(--color-primary);
  color: #fff;
}

.btn-sm {
  padding: 6px 14px;
  font-size: 0.85rem;
}

/* ===== Cards ===== */
.card {
  background: var(--color-white);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition), transform var(--transition);
  overflow: hidden;
}

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

.card-body {
  padding: 24px;
}

.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 28px;
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
}

.grid-4 {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}

.badge {
  display: inline-block;
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 0.8rem;
  font-weight: 600;
}

.badge-primary {
  background: var(--color-primary);
  color: #fff;
}

.badge-accent {
  background: var(--color-accent);
  color: #fff;
}

.badge-outline {
  background: transparent;
  border: 1px solid var(--color-border);
  color: var(--color-text-light);
}

.year-filter {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 32px;
}

.year-filter a {
  padding: 6px 16px;
  border-radius: 20px;
  border: 1px solid var(--color-border);
  color: var(--color-text);
  font-size: 0.9rem;
  font-weight: 500;
  transition: all var(--transition);
}

.year-filter a:hover,
.year-filter a.active {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}

.paper-item {
  background: var(--color-white);
  border-radius: var(--radius-md);
  padding: 24px;
  box-shadow: var(--shadow-sm);
  border-left: 4px solid transparent;
  transition: all var(--transition);
  margin-bottom: 16px;
}

.paper-item:hover {
  box-shadow: var(--shadow-md);
  border-left-color: var(--color-primary);
}

.paper-item .paper-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--color-primary-dark);
  margin-bottom: 8px;
}

.paper-item .paper-title a {
  color: inherit;
}

.paper-item .paper-title a:hover {
  color: var(--color-primary-light);
}

.paper-item .paper-meta {
  font-size: 0.9rem;
  color: var(--color-text-light);
  margin-bottom: 8px;
}

.paper-item .paper-journal {
  font-style: italic;
  font-weight: 600;
}

.paper-item .paper-abstract {
  font-size: 0.93rem;
  color: var(--color-text-light);
  line-height: 1.7;
  margin-top: 8px;
}

.paper-item .paper-tags {
  margin-top: 12px;
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
}

.featured-paper {
  background: var(--color-white);
  border-radius: var(--radius-md);
  padding: 24px;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition);
}

.featured-paper:hover {
  box-shadow: var(--shadow-md);
}

.featured-paper h3 {
  font-size: 1.05rem;
  margin-bottom: 6px;
  color: var(--color-primary-dark);
}

.featured-paper h3 a {
  color: inherit;
}

.featured-paper h3 a:hover {
  color: var(--color-primary-light);
}

.featured-paper .journal {
  font-size: 0.85rem;
  color: var(--color-text-light);
  font-style: italic;
}

.member-card {
  background: var(--color-white);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  padding: 28px 24px;
  text-align: center;
  transition: all var(--transition);
}

.member-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-3px);
}

.member-avatar {
  width: 100px;
  height: 100px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-light));
  color: #fff;
  font-size: 2.2rem;
  font-weight: 700;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 16px;
  overflow: hidden;
  flex-shrink: 0;
}

.member-avatar img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  border-radius: 50%;
}

.member-card h3 {
  font-size: 1.1rem;
  color: var(--color-primary-dark);
  margin-bottom: 4px;
}

.member-card .member-title {
  font-size: 0.88rem;
  color: var(--color-text-light);
  margin-bottom: 12px;
}

.member-card .member-bio {
  font-size: 0.9rem;
  color: var(--color-text-light);
  line-height: 1.6;
}

.software-card {
  background: var(--color-white);
  border-radius: var(--radius-md);
  padding: 28px;
  box-shadow: var(--shadow-sm);
  transition: all var(--transition);
  display: flex;
  flex-direction: column;
}

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

.software-card h3 {
  font-size: 1.2rem;
  color: var(--color-primary-dark);
  margin-bottom: 8px;
}

.software-card .version {
  font-size: 0.85rem;
  color: var(--color-text-light);
  margin-bottom: 12px;
}

.software-card .description {
  font-size: 0.93rem;
  color: var(--color-text-light);
  line-height: 1.7;
  flex-grow: 1;
  margin-bottom: 16px;
}

.software-card .software-links {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.admission-card {
  background: var(--color-white);
  border-radius: var(--radius-md);
  padding: 32px;
  box-shadow: var(--shadow-sm);
  margin-bottom: 24px;
  border-top: 4px solid var(--color-primary);
}

.admission-card h2 {
  font-size: 1.4rem;
  color: var(--color-primary-dark);
  margin-bottom: 12px;
}

.admission-card p,
.admission-card li {
  font-size: 1rem;
  color: var(--color-text-light);
  line-height: 1.8;
}

.admission-card ul {
  list-style: disc;
  padding-left: 24px;
  margin: 8px 0;
}

.pub-detail-header {
  background: var(--color-white);
  padding: 48px 0;
  box-shadow: var(--shadow-sm);
}

.pub-detail-header h1 {
  font-size: 1.8rem;
  color: var(--color-primary-dark);
  margin-bottom: 12px;
  line-height: 1.4;
}

.pub-detail-meta {
  color: var(--color-text-light);
  font-size: 1rem;
  margin-bottom: 16px;
}

.pub-detail-meta .journal {
  font-style: italic;
  font-weight: 600;
}

.pub-detail-content {
  padding: 40px 0;
}

.pub-detail-content .abstract {
  font-size: 1.05rem;
  line-height: 1.8;
  color: var(--color-text);
}

.pub-detail-content h2 {
  font-size: 1.3rem;
  color: var(--color-primary-dark);
  margin-bottom: 16px;
}

.breadcrumb {
  padding: 16px 0;
  font-size: 0.9rem;
  color: var(--color-text-light);
}

.breadcrumb a {
  color: var(--color-primary-light);
}

.breadcrumb span {
  margin: 0 8px;
}

.site-footer {
  background: #1a3a5c;
  color: rgba(255,255,255,0.85);
  padding: 48px 0 24px;
  margin-top: 60px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  margin-bottom: 32px;
}

.footer-col h3 {
  color: #fff;
  font-size: 1.15rem;
  margin-bottom: 16px;
}

.footer-col p,
.footer-col li {
  font-size: 0.93rem;
  line-height: 1.8;
}

.footer-col a {
  color: rgba(255,255,255,0.7);
}

.footer-col a:hover {
  color: #fff;
}

.footer-col address {
  font-style: normal;
}

.footer-col ul li {
  margin-bottom: 4px;
}

.footer-bottom {
  border-top: 1px solid rgba(255,255,255,0.15);
  padding-top: 20px;
  text-align: center;
  font-size: 0.88rem;
  color: rgba(255,255,255,0.55);
}

@media (max-width: 1024px) {
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .footer-grid { grid-template-columns: repeat(2, 1fr); }
  .hero h1 { font-size: 2.4rem; }
  .hero-stats { gap: 28px; }
}

@media (max-width: 768px) {
  .nav-desktop { display: none; }
  .nav-toggle { display: flex; }
  .grid-2, .grid-3 { grid-template-columns: 1fr; }
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .footer-grid { grid-template-columns: 1fr; gap: 28px; }
  .hero { padding: 70px 0 60px; }
  .hero h1 { font-size: 2rem; }
  .hero p { font-size: 1.05rem; }
  .hero-stats { gap: 18px; }
  .hero-stat .stat-num { font-size: 1.5rem; }
  .section { padding: 40px 0; }
  .section-title { font-size: 1.5rem; }
  .pub-detail-header h1 { font-size: 1.4rem; }
}

@media (max-width: 480px) {
  .grid-4 { grid-template-columns: 1fr; }
  .hero-actions { flex-direction: column; align-items: center; }
  .hero { padding: 50px 0 40px; }
  .hero h1 { font-size: 1.6rem; }
  .paper-item { padding: 16px; }
  .container { padding: 0 16px; }
}