manual-markdown/book/gitbook/gitbook-plugin-chapter-fold/chapter-fold.css

Markdown 是一种轻量级的标记语言。它允许使用易读易写的纯文本格式编写文档，然后转换成 HTML 文档。

.book .book-summary .chapter > .articles {
	overflow: hidden;
	max-height: 0px;
}

.book .book-summary .chapter.expanded > .articles {
	max-height: 9999px;
}

.book .book-summary .exc-trigger {
	position: absolute;
  	left: 12px;
  	top: 12px;
}

.book .book-summary ul.summary li a,
.book .book-summary ul.summary li span {
	padding-left: 30px;
}

.book .book-summary .exc-trigger:before {
  	content: "\f105";
}

.book .book-summary .expanded > a .exc-trigger:before,
.book .book-summary .expanded > span .exc-trigger:before {
	content: "\f107";
}