/* AI学术之家 · Academic-style UI
   Palette: Tech Blue + Academic Black (matches provided logo)
*/

:root{
  --bg: #f7f9fb;
  --card: #ffffff;
  --text: #1f2328;
  --muted: #586069;
  --border: #e3e6eb;
  --blue: #0a4fb3;
  --blue2: #1677ff;
}

*{box-sizing:border-box;}
html,body{height:100%;}
body{
  margin:0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB",
               "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
}

.site-header{
  position: sticky;
  top: 0;
  z-index: 20;
  background: rgba(255,255,255,.92);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}

.header-inner{
  max-width: 1200px;
  margin: 0 auto;
  padding: 14px 20px;
  display:flex;
  justify-content: space-between;
  align-items:center;
  gap:16px;
}

.logo-area{
  display:flex;
  align-items:center;
  gap:14px;
  min-width: 260px;
}

.logo-link{
  display:flex;
  align-items:center;
  gap:10px;
  text-decoration:none;
  color:inherit;
}

.logo-area img{
  height: 100px;
  width:auto;
  display:block;
}

.site-title{
  font-size: 20px;
  font-weight: 700;
  letter-spacing: .2px;
  color: var(--blue);
}

.site-subtitle{
  font-size: 12px;
  color: var(--muted);
  white-space: nowrap;
}

.main-nav{
  display:flex;
  flex-wrap:wrap;
  justify-content:flex-end;
  gap: 18px;
}

.main-nav a{
  text-decoration:none;
  color: var(--text);
  font-size: 14px;
  padding: 8px 10px;
  border-radius: 8px;
  border: 1px solid transparent;
}

.main-nav a:hover{
  color: var(--blue);
  border-color: rgba(10,79,179,.20);
  background: rgba(10,79,179,.06);
}

.main-nav a.active{
  color: var(--blue);
  background: rgba(10,79,179,.08);
  border-color: rgba(10,79,179,.25);
  font-weight: 600;
}

.container{
  max-width: 1200px;
  margin: 28px auto 60px;
  padding: 0 20px;
}

.hero{
  background: linear-gradient(180deg, rgba(10,79,179,.08), rgba(10,79,179,0));
  border: 1px solid rgba(10,79,179,.14);
  border-radius: 14px;
  padding: 22px 22px 18px;
  margin-bottom: 26px;
}

.hero h1{
  margin: 0 0 8px;
  font-size: 26px;
  letter-spacing: .2px;
}

.hero p{
  margin: 0 0 14px;
  color: var(--muted);
  line-height: 1.6;
}

.hero .meta{
  display:flex;
  align-items:center;
  gap:10px;
  color: var(--muted);
  font-size: 13px;
}

.hero .dot{opacity:.8;}

.category{
  margin: 30px 0 44px;
}

.category h2{
  font-size: 18px;
  margin: 0 0 14px;
  padding-left: 12px;
  border-left: 4px solid var(--blue);
  letter-spacing: .2px;
}

.site-list{
  display:grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 14px;
}

.site-card{
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 14px 14px 12px;
  box-shadow: 0 1px 0 rgba(27,31,35,.04);
  transition: transform .08s ease, border-color .08s ease, box-shadow .08s ease;
  min-height: 110px;
}

.site-card:hover{
  transform: translateY(-1px);
  border-color: rgba(10,79,179,.28);
  box-shadow: 0 8px 20px rgba(27,31,35,.07);
}

.site-card a{
  display:inline-block;
  font-weight: 700;
  color: var(--blue);
  text-decoration:none;
  line-height: 1.25;
}

.site-card a:hover{ color: var(--blue2); text-decoration: underline; }

.site-card .no-link{
  display:inline-block;
  font-weight: 700;
}

.site-card p{
  margin: 8px 0 10px;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.55;
  min-height: 40px;
}

.site-url{
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  font-size: 11px;
  color: #7a828e;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  border-top: 1px dashed rgba(227,230,235,.9);
  padding-top: 8px;
}

.site-footer{
  background:#ffffff;
  border-top: 1px solid var(--border);
  padding: 22px 0;
}

.footer-inner{
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
  display:flex;
  justify-content: space-between;
  gap: 20px;
  flex-wrap: wrap;
  color: var(--muted);
  font-size: 13px;
}

.footer-brand{
  color: var(--text);
  font-weight: 700;
  margin-bottom: 6px;
}

.footer-note{
  margin-top: 6px;
  font-size: 12px;
  color: #7a828e;
}

/* Responsive */
@media (max-width: 820px){
  .header-inner{flex-direction: column; align-items: flex-start;}
  .main-nav{justify-content:flex-start;}
  .logo-area{min-width: auto;}
}