/* SCROLL 指示器 → 回顶按钮
   ⚠️ .heading-2 与 .image-3 的竖排全靠基础 rotate(90deg)，
   所有状态变换必须带上这一基础旋转，否则文字会"反向转正"、箭头停在朝左 */
.scroll-arrow {
  pointer-events: none;
}

.scroll-arrow .heading-2,
.scroll-arrow .image-3 {
  transition:
    opacity .45s ease,
    transform .65s cubic-bezier(.16, .72, .26, 1);
}

.scroll-arrow.nvh-st-up {
  pointer-events: auto;
  cursor: pointer;
}

/* 文字：保持竖排姿态，沿箭头方向（屏幕向下）滑出并淡隐 */
.scroll-arrow.nvh-st-up .heading-2 {
  opacity: 0;
  transform: translateY(20px) rotate(90deg);
}

/* 箭头：90° → -90°，原地自旋 180°，收尾朝上 */
.scroll-arrow.nvh-st-up .image-3 {
  transform: rotate(-90deg);
}

@media (hover: hover) and (pointer: fine) {
  .scroll-arrow.nvh-st-up:hover .image-3 {
    transform: translateY(-6px) rotate(-90deg);
  }
}

@media (prefers-reduced-motion: reduce) {
  .scroll-arrow .heading-2,
  .scroll-arrow .image-3 {
    transition: none;
  }
}