:root {
  --bg: #f8f9fa;
  --panel: #ffffff;
  --text: #212529;
  --muted: #6c757d;
  --brand: #6750a4;
  --sit-brand: #4dabf7; /* 软件安装教程 - 浅蓝色 */
  --sip-brand: #ff6b9c; /* 软件整合包 - 浅粉色 */
  --tjd-brand: #7952b3; /* Java文档 - 高级感紫色 */
  --card: #ffffff;
  --card-border: #dee2e6;
  --divider: #ced4da;
}

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

.site-header { max-width: 1200px; margin: 0 auto; padding: 24px 16px 8px; }
.brand { display: flex; align-items: center; gap: 16px; }
.logo { width: 56px; height: 56px; border-radius: 12px; border: 1px solid var(--card-border); background: #fff; }
.titles .title { margin: 0; font-size: 28px; letter-spacing: 1px; }
.titles .subtitle { margin: 4px 0 0; color: var(--muted); font-size: 14px; }

.site-nav { 
  margin-top: 16px; 
  display: flex; 
  gap: 12px; 
  flex-wrap: wrap; 
  justify-content: space-between;
}
@media (max-width: 780px) {
  .site-nav {
    justify-content: center;
  }
}
.site-nav a {
  color: var(--text);
  text-decoration: none;
  padding: 12px 20px;
  border-radius: 12px;
  border: 1px solid var(--card-border);
  background: var(--card);
  font-weight: 600;
  transition: all 0.2s ease;
  box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}
.site-nav a:hover { 
  border-color: var(--brand); 
background: rgba(103, 80, 164, 0.08);
  transform: translateY(-2px);
  box-shadow: 0 4px 8px rgba(0,0,0,0.1);
}
.site-nav a.sit-primary { 
  background: var(--sit-brand); 
  color: #ffffff; 
  font-weight: 600; 
  border: 1px solid var(--sit-brand);
  flex: 1;
  text-align: center;
}
.site-nav a.sit-primary:hover { 
  filter: brightness(0.95); 
  transform: translateY(-2px);
box-shadow: 0 4px 12px rgba(77, 171, 247, 0.3);
}

.site-nav a.sip-primary { 
  background: var(--sip-brand); 
  color: #ffffff; 
  font-weight: 600; 
  border: 1px solid var(--sip-brand);
  flex: 1;
  text-align: center;
}
.site-nav a.sip-primary:hover { 
  filter: brightness(0.95); 
  transform: translateY(-2px);
box-shadow: 0 4px 12px rgba(255, 107, 156, 0.3);
}

.site-nav a.tjd-primary { 
  background: var(--tjd-brand); 
  color: #ffffff; 
  font-weight: 600; 
  border: 1px solid var(--tjd-brand);
  flex: 1;
  text-align: center;
}
.site-nav a.tjd-primary:hover { 
  filter: brightness(0.95); 
  transform: translateY(-2px);
box-shadow: 0 4px 12px rgba(121, 82, 179, 0.3);
}

@media (max-width: 780px) {
  .site-nav a {
    flex: none;
  }
}

.hero { margin-top: 20px; background: var(--panel); border: 1px solid var(--card-border); border-radius: 16px; padding: 24px; }
.hero h2 { margin: 0 0 8px; font-size: 22px; }
.hero p { margin: 0; color: var(--muted); }
.hero .hero-actions { margin-top: 16px; }
.btn { display: inline-block; padding: 10px 16px; background: var(--brand); color: #ffffff; border-radius: 10px; text-decoration: none; font-weight: 600; }
.btn:hover { filter: brightness(0.95); }

.divider { height: 1px; background: var(--divider); margin: 20px 0 0; }

.site-main { max-width: 1200px; margin: 0 auto; padding: 8px 16px 40px; }
.section { margin-top: 28px; }
.section-head h3 { margin: 0 0 6px; font-size: 18px; }
.section-head p { margin: 0 0 12px; color: var(--muted); font-size: 13px; }

.cards { display: grid; grid-template-columns: repeat(4, 1fr); gap: 14px; }
@media (max-width: 1080px) { .cards { grid-template-columns: repeat(3, 1fr); } }
@media (max-width: 780px) { .cards { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 520px) { .cards { grid-template-columns: 1fr; } }

.card { display: block; background: var(--card); border: 1px solid var(--card-border); border-radius: 14px; padding: 14px; text-decoration: none; color: var(--text); transition: transform .1s ease, background .2s ease, border-color .2s ease; }
.card:hover { transform: translateY(-2px); background: #f1f3f5; border-color: #ced4da; }
.card h4 { margin: 0 0 6px; font-size: 16px; }
.card p { margin: 0; color: var(--muted); font-size: 13px; line-height: 1.5; }
.card.more { outline: 1px dashed #2a5f43; outline-offset: -6px; }

.site-footer { max-width: 1200px; margin: 0 auto; padding: 0 16px 32px; text-align: center; color: var(--muted); font-size: 13px; }
.site-footer .divider { margin-top: 0; margin-bottom: 14px; }