/* ========================================
   页脚样式
   ======================================== */

footer {
  position: relative;
  background: radial-gradient(circle at top, rgba(176, 190, 197, 0.2), transparent 45%),
              linear-gradient(160deg, #0f1b25, #1b2b38 60%, #0c141d);
  color: var(--color-white);
  margin-top: var(--spacing-5xl);
  padding: var(--spacing-4xl) 0 var(--spacing-3xl);
  overflow: hidden;
}

footer::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(120deg, rgba(255, 255, 255, 0.15), transparent);
  opacity: 0.5;
  pointer-events: none;
}

.footer-container {
  max-width: var(--container-xl);
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
}

.footer-content {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--spacing-2xl);
  margin-bottom: var(--spacing-3xl);
  padding-bottom: var(--spacing-3xl);
  border-bottom: 1px solid rgba(255, 255, 255, 0.15);
  position: relative;
  z-index: 1;
}

.footer-section h3 {
  color: var(--color-white);
  font-size: var(--font-size-lg);
  margin-bottom: var(--spacing-lg);
  text-transform: uppercase;
  letter-spacing: 0.12em;
}

.footer-section p {
  color: rgba(255, 255, 255, 0.8);
  font-size: var(--font-size-sm);
  line-height: var(--line-height-relaxed);
}

.footer-section ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.footer-section li {
  margin-bottom: var(--spacing-md);
  color: rgba(255, 255, 255, 0.8);
}

.footer-section a {
  color: rgba(255, 255, 255, 0.8);
  text-decoration: none;
  transition: all var(--transition-fast);
  position: relative;
}

.footer-section a:hover {
  color: var(--color-accent);
  padding-left: var(--spacing-sm);
}

/* 联系信息 */
.contact-info {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.contact-item {
  display: flex;
  align-items: flex-start;
  gap: var(--spacing-md);
}

.contact-icon {
  width: 24px;
  height: 24px;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-accent);
  font-weight: var(--font-weight-bold);
  background: rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-full);
}

.contact-text {
  color: rgba(255, 255, 255, 0.8);
  font-size: var(--font-size-sm);
}

/* 社交媒体 */
.social-links {
  display: flex;
  gap: var(--spacing-lg);
  margin-top: var(--spacing-lg);
}

.social-link {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: rgba(255, 255, 255, 0.12);
  border-radius: var(--radius-full);
  color: var(--color-white);
  text-decoration: none;
  transition: all var(--transition-fast);
  border: 1px solid rgba(255, 255, 255, 0.2);
}

.social-link:hover {
  background-color: var(--color-accent);
  border-color: var(--color-accent);
  transform: translateY(-4px);
}

/* 底部栏 */
.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: var(--spacing-2xl);
  border-top: 1px solid rgba(255, 255, 255, 0.15);
  flex-wrap: wrap;
  gap: var(--spacing-lg);
  position: relative;
  z-index: 1;
}

.footer-copyright {
  color: rgba(255, 255, 255, 0.6);
  font-size: var(--font-size-sm);
}

.footer-links {
  display: flex;
  gap: var(--spacing-2xl);
  list-style: none;
  padding: 0;
  margin: 0;
}

.footer-links a {
  color: rgba(255, 255, 255, 0.6);
  text-decoration: none;
  font-size: var(--font-size-sm);
  transition: all var(--transition-fast);
}

.footer-links a:hover {
  color: var(--color-accent);
}

/* 返回顶部按钮 */
.back-to-top {
  position: fixed;
  bottom: var(--spacing-lg);
  right: var(--spacing-lg);
  width: 48px;
  height: 48px;
  background-image: linear-gradient(135deg, var(--color-secondary-dark), var(--color-primary-dark));
  color: var(--color-white);
  border: none;
  border-radius: var(--radius-full);
  font-size: var(--font-size-lg);
  cursor: pointer;
  display: none;
  align-items: center;
  justify-content: center;
  box-shadow: 0 20px 45px rgba(38, 50, 56, 0.25);
  transition: all var(--transition-fast);
  z-index: var(--z-fixed);
}

.back-to-top.show {
  display: flex;
}

.back-to-top:hover {
  transform: translateY(-4px);
  box-shadow: 0 25px 55px rgba(38, 50, 56, 0.35);
}

/* 响应式设计 */
@media (max-width: 1024px) {
  .footer-content {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 640px) {
  footer {
    padding: var(--spacing-2xl) 0 var(--spacing-xl);
  }
  
  .footer-content {
    grid-template-columns: 1fr;
    gap: var(--spacing-xl);
    margin-bottom: var(--spacing-2xl);
    padding-bottom: var(--spacing-2xl);
  }
  
  .footer-bottom {
    flex-direction: column;
    align-items: flex-start;
  }
  
  .footer-links {
    flex-direction: column;
    gap: var(--spacing-lg);
  }
  
  .back-to-top {
    width: 40px;
    height: 40px;
    font-size: var(--font-size-base);
    bottom: var(--spacing-md);
    right: var(--spacing-md);
  }
}