/* ===== 布局：导航 / 页脚 / 网格 / 响应式 ===== */

/* 导航栏 */
.navbar {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  height: var(--nav-height);
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  display: flex; align-items: center;
}
.navbar .nav-inner {
  width: 100%; max-width: 1200px; margin: 0 auto;
  padding: 0 var(--space-4);
  display: flex; align-items: center; justify-content: space-between;
}
.navbar .logo {
  display: flex; align-items: center; gap: var(--space-2);
  font-weight: 800; font-size: var(--font-size-lg);
  color: var(--color-primary-dark);
}
.navbar .logo .logo-icon { font-size: var(--font-size-xl); }
.navbar .nav-links { display: none; gap: var(--space-1); }
.navbar .nav-links a {
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-md);
  color: var(--color-text-secondary);
  font-weight: 500; font-size: var(--font-size-sm);
  transition: all var(--transition-fast);
}
.navbar .nav-links a:hover,
.navbar .nav-links a.active {
  background: var(--color-primary-muted);
  color: var(--color-primary-dark);
}
.nav-toggle {
  display: flex; flex-direction: column; gap: 5px;
  background: none; border: none; cursor: pointer; padding: var(--space-2);
}
.nav-toggle span {
  width: 24px; height: 2px; background: var(--color-text-primary);
  border-radius: 2px; transition: all var(--transition-fast);
}
.nav-toggle.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle.open span:nth-child(2) { opacity: 0; }
.nav-toggle.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* 移动端菜单 */
.mobile-menu {
  display: none; flex-direction: column; gap: var(--space-1);
  padding: var(--space-4);
  background: var(--color-bg-surface);
  border-bottom: 1px solid var(--color-border);
}
.mobile-menu.open { display: flex; }
.mobile-menu a {
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-md);
  color: var(--color-text-secondary);
  font-weight: 500;
}
.mobile-menu a:hover, .mobile-menu a.active {
  background: var(--color-primary-muted);
  color: var(--color-primary-dark);
}

@media (min-width: 768px) {
  .navbar .nav-links { display: flex; }
  .nav-toggle { display: none; }
}

/* 页脚 */
.footer {
  background: var(--color-text-primary);
  color: rgba(255,255,255,0.7);
  padding: var(--space-7) var(--space-4) var(--space-5);
  margin-top: var(--space-8);
}
.footer .footer-inner {
  max-width: 1200px; margin: 0 auto;
  text-align: center;
}
.footer .footer-links {
  display: flex; flex-wrap: wrap; justify-content: center; gap: var(--space-4);
  margin-bottom: var(--space-4);
}
.footer .footer-links a { color: rgba(255,255,255,0.8); font-size: var(--font-size-sm); }
.footer .footer-links a:hover { color: var(--color-primary-light); }
.footer .attribution {
  font-size: var(--font-size-xs); color: rgba(255,255,255,0.5);
  margin-top: var(--space-3);
}
.footer .attribution a { color: rgba(255,255,255,0.6); }

/* 主内容区 */
.main-content { min-height: calc(100vh - var(--nav-height) - 200px); }

/* 区段 */
.section { padding: var(--space-6) 0; }
.section-header { text-align: center; margin-bottom: var(--space-6); }
.section-header h2 { margin-bottom: var(--space-2); }
.section-header p { color: var(--color-text-secondary); max-width: 600px; margin: 0 auto; }

/* 网格 */
.grid { display: grid; gap: var(--space-4); }
.grid-2 { grid-template-columns: 1fr; }
.grid-3 { grid-template-columns: 1fr; }
.grid-4 { grid-template-columns: 1fr; }

@media (min-width: 640px) {
  .grid-2 { grid-template-columns: repeat(2, 1fr); }
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
}
@media (min-width: 1024px) {
  .grid-3 { grid-template-columns: repeat(3, 1fr); }
  .grid-4 { grid-template-columns: repeat(3, 1fr); }
}
@media (min-width: 1280px) {
  .grid-4 { grid-template-columns: repeat(4, 1fr); }
}

/* Flex 工具 */
.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.justify-center { justify-content: center; }
.flex-wrap { flex-wrap: wrap; }
.gap-2 { gap: var(--space-2); }
.gap-4 { gap: var(--space-4); }