https://www.cnblogs.com/shenxiaolin/p/7244423.html
https://blog.csdn.net/wangjiankun_ls/article/details/70491633
[$\bullet$]这是圆点符号
\begin{itemize}\item[$\bigstar$] The idea is
\item[$\bigstar$] However, we
\item[$\blacktriangleright$] Instead we take
\item[$\blacktriangleright$] Might loook difficult \end{itemize}