/* ========================================
   页脚
   ======================================== */

.footer {
  padding: var(--space-2xl) 0;
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
}

.footer-content {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--space-md);
}

.footer-brand {
  font-size: var(--text-lg);
  font-weight: 700;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
}

.footer-links {
  display: flex;
  gap: var(--space-lg);
}

.footer-link {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}

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

.footer-copyright {
  font-size: var(--text-sm);
  color: var(--text-tertiary);
}

/* ========================================
   回到顶部
   ======================================== */

.back-to-top {
  position: fixed;
  bottom: 32px;
  right: 32px;
  width: 44px;
  height: 44px;
  border-radius: var(--radius-full);
  background: var(--color-primary);
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-lg);
  box-shadow: var(--shadow-lg);
  opacity: 0;
  visibility: hidden;
  transform: translateY(10px);
  transition: all var(--transition-normal);
  z-index: 999;
  cursor: pointer;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  background: var(--color-primary-dark);
  transform: translateY(-2px);
}

/* ========================================
   响应式设计
   ======================================== */

@media (max-width: 1024px) {
  .categories-grid {
    grid-template-columns: repeat(4, 1fr);
  }

  .tools-grid {
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  }
}

@media (max-width: 768px) {
  :root {
    --nav-height: 56px;
  }

  .container {
    padding: 0 var(--space-md);
  }

  .nav-search {
    display: none;
  }

  .nav-submit-btn span {
    display: none;
  }

  .hero {
    padding: var(--space-2xl) 0;
  }

  .hero-title {
    font-size: var(--text-3xl);
  }

  .hero-search-input {
    height: 48px;
  }

  .hero-stats {
    gap: var(--space-lg);
  }

  .hero-stat-value {
    font-size: var(--text-2xl);
  }

  .categories-grid {
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-sm);
  }

  .category-card {
    padding: var(--space-md) var(--space-sm);
  }

  .category-card .category-desc {
    display: none;
  }

  .tools-grid {
    grid-template-columns: 1fr;
    gap: var(--space-md);
  }

  .filter-bar {
    overflow-x: auto;
    flex-wrap: nowrap;
    padding-bottom: var(--space-md);
    -webkit-overflow-scrolling: touch;
  }

  .filter-bar::-webkit-scrollbar {
    display: none;
  }

  .section {
    padding: var(--space-2xl) 0;
  }

  .footer-content {
    flex-direction: column;
    text-align: center;
  }
}

@media (max-width: 480px) {
  .categories-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .hero-stats {
    gap: var(--space-md);
  }

  .hero-stat-value {
    font-size: var(--text-xl);
  }
}