/* 统一的返回顶部控件。
 * 具体页面只负责决定是否加载组件，显示条件和按钮层级由 site-scroll-top.js 统一管理。
 */
.site-scroll-top {
  position: fixed;
  right: 52px;
  bottom: 92px;
  z-index: 1170;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  width: auto;
  min-width: 48px;
  height: 44px;
  min-height: 44px;
  padding: 0 14px;
  box-sizing: border-box;
  border: 1px solid rgba(148, 163, 184, .28);
  border-radius: 999px;
  background: rgba(255, 255, 255, .96);
  color: #0a4a63;
  box-shadow: 0 10px 26px rgba(15, 23, 42, .14);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transform: translateY(10px);
  transition: opacity .22s ease, transform .22s ease, visibility .22s,
    color .18s ease, border-color .18s ease, box-shadow .18s ease;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.site-scroll-top[hidden] {
  display: none !important;
}

.site-scroll-top.is-visible {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  transform: translateY(0);
}

.site-scroll-top:hover {
  color: #0a4a63;
  border-color: rgba(148, 163, 184, .28);
  background: rgba(255, 255, 255, .96);
  box-shadow: 0 14px 32px rgba(15, 119, 214, .24);
  transform: translateY(-2px) scale(1.02);
}

.site-scroll-top:focus-visible {
  outline: 3px solid rgba(0, 172, 235, .35);
  outline-offset: 3px;
  box-shadow: 0 14px 32px rgba(15, 119, 214, .24);
}

.site-scroll-top svg {
  width: 19px;
  height: 19px;
  display: block;
  flex: 0 0 auto;
  overflow: visible;
  stroke: currentColor;
}

.site-scroll-top-label {
  display: inline;
  font-size: 13px;
  font-weight: 700;
  line-height: 1;
  white-space: nowrap;
}

/* 社区页右下角顺序：悬浮导航 → 发帖 → 返回顶部 → 回复提醒。 */
body[data-page="forum"] .site-scroll-top {
  bottom: 146px;
}

body[data-page="forum"] .floating-forum-replies {
  bottom: 202px;
}

@media (max-width: 768px) {
  .site-scroll-top {
    right: 40px;
    bottom: 88px;
    width: 44px;
    min-width: 44px;
    height: 44px;
    min-height: 44px;
    padding: 0;
    border-radius: 50%;
  }

  .site-scroll-top svg {
    width: 18px;
    height: 18px;
  }

  .site-scroll-top-label {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
  }

  body.mobile-page[data-page="forum"] .site-scroll-top {
    bottom: 132px;
  }

  body.mobile-page[data-page="forum"] .floating-forum-replies {
    bottom: 180px;
  }
}

@media (prefers-reduced-motion: reduce) {
  .site-scroll-top {
    transition: none;
  }
}