/* 1. 顶部进度条 */
.scroll-progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  background: #0070f3; /* 进度条颜色 */
  width: 0%;
  z-index: 9999;
  transition: width 0.1s linear;
}

/* 2. 圆形按钮容器 */
.top-btn {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 50px;
  height: 50px;
  border-radius: 50%; /* 完美圆形 */
  background: #ffffff;
  cursor: pointer;
  z-index: 9998;
  border: 1px solid #eaeaea;
  padding: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
  transition:
    transform 0.2s ease,
    box-shadow 0.2s ease;
}

.top-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.15);
}

/* 3. 环形进度条 SVG */
.progress-circle {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  transform: rotate(-90deg); /* 从顶部开始绘制 */
  pointer-events: none; /* 让点击穿透到按钮 */
}

.progress-circle circle {
  fill: none;
  stroke: #0070f3; /* 环形进度颜色 */
  stroke-width: 4;
  stroke-dasharray: 283; /* 2 * PI * 45 (半径) ≈ 283 */
  stroke-dashoffset: 283;
  transition: stroke-dashoffset 0.1s linear;
}

/* 4. 内部箭头图标 */
#arrowIcon {
  color: #333;
  transition: transform 0.3s ease; /* 实现箭头旋转动画 */
}