/* 回到顶部按钮样式 */
.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 50px;
  height: 50px;
  background: var(--color-btn-bg);
  border: 1px solid var(--color-btn-border);
  border-radius: 50%;
  cursor: pointer;
  z-index: 1000;
  opacity: 0;
  visibility: hidden;
  transition: all 0.3s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--color-btn-text);
  font-size: 18px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

.back-to-top:hover {
  background: var(--color-btn-hover-bg);
  border-color: var(--color-btn-hover-border);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.back-to-top.show {
  opacity: 1;
  visibility: visible;
}

/* 暗色主题适配 */
[data-color-mode="dark"] .back-to-top {
  background: var(--color-canvas-subtle);
  border-color: var(--color-border-default);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
}

[data-color-mode="dark"] .back-to-top:hover {
  background: var(--color-btn-hover-bg);
  border-color: var(--color-btn-hover-border);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.4);
}

/* 移动端适配 */
@media (max-width: 768px) {
  .back-to-top {
    bottom: 20px;
    right: 20px;
    width: 45px;
    height: 45px;
    font-size: 16px;
  }
}

/* SVG 图标样式 */
.back-to-top svg {
  width: 30px;
  height: 30px;
  fill: currentColor;
  transition: transform 0.2s ease;
}

.back-to-top:hover svg {
  transform: translateY(-1px);
}

/* 点击动画 */
.back-to-top:active {
  transform: translateY(0);
  transition: transform 0.1s ease;
}

/* 滚动动画 */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.back-to-top.show {
  animation: fadeInUp 0.3s ease;
}