/* 回到顶部按钮样式（原生，无构建依赖） */
.btt-global,
.btt-media {
  position: fixed;
  z-index: 9999;
  cursor: pointer;
  border: none;
  color: #fff;
  background-color: var(--accent-color, #009933);
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.28);
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.25s ease, visibility 0.25s ease, background-color 0.2s ease, transform 0.2s ease;
  font-family: inherit;
  -webkit-tap-highlight-color: transparent;
}

.btt-global:hover,
.btt-media:hover {
  background-color: var(--accent-color-hover, #007a29);
}

/* 1) 全局悬浮圆形图标按钮（右下角） */
.btt-global {
  right: 24px;
  bottom: 24px;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 0;
}

.btt-global .material-icons {
  font-size: 28px;
  line-height: 1;
}

/* 2) 视频内容页按钮（视口底部居中，仅媒体页显示） */
.btt-media {
  left: 50%;
  bottom: 24px;
  transform: translateX(-50%) translateY(8px);
  padding: 10px 20px;
  border-radius: 22px;
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.02em;
}

/* 显示态 */
.btt-global.is-visible {
  opacity: 1;
  visibility: visible;
}

.btt-media.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateX(-50%) translateY(0);
}

/* 小屏适配：避免两个按钮重叠，媒体页按钮上移 */
@media (max-width: 600px) {
  .btt-global {
    right: 14px;
    bottom: 14px;
    width: 42px;
    height: 42px;
  }
  .btt-media {
    bottom: 66px;
    font-size: 13px;
    padding: 8px 16px;
  }
}