BeamerTheme/beamerthemeSimple.sty

% !TEX program = xelatex
% !TEX TS-program = xelatex
% fonts
\RequirePackage{fontspec}
% \usefonttheme{professionalfonts}
% \RequirePackage[sfdefault]{FiraSans}
\RequirePackage{FiraMono} 
\renewcommand{\rmfamily}{\sffamily}
% \RequirePackage[fakebold]{firamath-otf}
\RequirePackage{unicode-math}
\RequirePackage{amsmath}
\RequirePackage{amsthm}
\RequirePackage{amssymb}
\RequirePackage{inputenc}
\unimathsetup{math-style=ISO, bold-style=ISO, mathrm=sym}
\setsansfont{FiraGO}[BoldFont=* SemiBold, Numbers=Monospaced]
\setmathfont{Fira Math}[BoldFont=*-SemiBold]
% \setmathfont[range=bb]{XITS Math Bold}
\RequirePackage{xeCJK}
\setCJKmainfont{Source Han Sans SC}
\setCJKsansfont{Source Han Sans SC}
\setCJKmonofont{Source Han Sans SC}

\RequirePackage[english]{babel}
\RequirePackage{fancyhdr}        % header footer
\RequirePackage[dvipsnames]{xcolor}
\RequirePackage{bookmark}
\RequirePackage{hyperref}[colorlinks=true,urlcolor=Blue,citecolor=Green,linkcolor=BrickRed,unicode]
\RequirePackage{natbib}
\RequirePackage{graphicx} % Allows including images
\RequirePackage{booktabs} % Allows the use of \toprule, \midrule and \bottomrule in tables
% \RequirePackage{tikz}
% \usetikzlibrary{backgrounds}
% \usetikzlibrary{arrows,shapes}
% \usetikzlibrary{tikzmark} % for \tikzmarknode
% \usetikzlibrary{calc} % for computing the midpoint between two nodes, e.g. at ($(p1.north)!0.5!(p2.north)$) 
% \RequirePackage[ruled,linesnumbered]{algorithm2e}
% \RequirePackage{adjustbox}
\RequirePackage{subcaption}
% \RequirePackage{CJKutf8}
% \def\zh#1{\begin{CJK}{UTF8}{gbsn}#1\end{CJK}}
\RequirePackage{aliascnt}

% a color box
\RequirePackage[breakable, theorems, skins]{tcolorbox}
\tcbset{enhanced}
\DeclareRobustCommand{\boxfill}[2][oliver!20]{%
\begin{tcolorbox}[   %% Adjust the following parameters at will.
        breakable,
        left=0pt,
        right=0pt,
        top=0pt,
        bottom=0pt,
        colback=#1,
        colframe=#1,
        width=\dimexpr\textwidth\relax, 
        enlarge left by=0mm,
        boxsep=5pt,
        arc=0pt,outer arc=0pt,
        ]
        #2
\end{tcolorbox}
}


\definecolor{beamer@simple@color}{RGB}{12 72 66} % bluegreen
\DeclareOptionBeamer{gray}{\definecolor{beamer@simple@color}{gray}{#1}}
\DeclareOptionBeamer{rgb}{\definecolor{beamer@simple@color}{rgb}{#1}}
\DeclareOptionBeamer{RGB}[{12 72 0}]{\definecolor{beamer@simple@color}{RGB}{#1}}
\DeclareOptionBeamer{HTML}{\definecolor{beamer@simple@color}{HTML}{#1}}
\DeclareOptionBeamer{cmyk}{\definecolor{beamer@simple@color}{cmyk}{#1}}
\DeclareOptionBeamer{cmy}{\definecolor{beamer@simple@color}{cmy}{#1}}
\DeclareOptionBeamer{named}{\definecolor{beamer@simple@color}{named}{#1}}
\DeclareOptionBeamer{hsb}{\definecolor{beamer@simple@color}{hsb}{#1}}
\ProcessOptionsBeamer
\definecolor{oliver}{rgb}{0.33, 0.42, 0.18} 

% footline
% delete navigation below
\setbeamertemplate{navigation symbols}{}

\useoutertheme{tree}
\makeatletter
\setbeamertemplate{headline}
{%
    \begin{beamercolorbox}[wd=\paperwidth,colsep=1.5pt]{upper separation line head}
    \end{beamercolorbox}
    \begin{beamercolorbox}[wd=\paperwidth,ht=2.5ex,dp=1.125ex,%
      leftskip=.3cm,rightskip=.3cm plus1fil]{title in head/foot}
      \usebeamerfont{title in head/foot}\insertshorttitle
      \usebeamerfont{section in head/foot}%
      \ifbeamer@tree@showhooks
        \setbox\beamer@tempbox=\hbox{\insertsectionhead}%
        \ifdim\wd\beamer@tempbox>1pt%
          \hskip2pt\raise1.9pt\hbox{\vrule width 5pt height0.4pt}%
          \hskip1pt%
        \fi%
      \else%  
        \hskip6pt%
      \fi%
      \insertsectionhead
      \usebeamerfont{subsection in head/foot}%
      \ifbeamer@tree@showhooks
        \setbox\beamer@tempbox=\hbox{\insertsubsectionhead}%
        \ifdim\wd\beamer@tempbox>1pt%
          \hskip2pt\raise1.9pt\hbox{\vrule width 5pt height0.4pt}%
          \hskip1pt%
        \fi%
      \else%  
        \hskip12pt%
      \fi%
      \insertsubsectionhead\hfill\insertshortauthor\hskip12pt\insertframenumber/\inserttotalframenumber\hspace{0.5em}
    \end{beamercolorbox}
    \begin{beamercolorbox}[wd=\paperwidth,colsep=1.5pt]{lower separation line head}
    \end{beamercolorbox}
}
\makeatother

% footline color
\setbeamercolor{author in head/foot}{fg=black, bg=mygrey!5!white}
\setbeamercolor{title in head/foot}{fg=black, bg=mygrey!5!white}
\setbeamercolor*{title}{fg=beamer@simple@color, bg=white}          
% item settings
\setbeamertemplate{itemize item}{$\color{beamer@simple@color}\bullet$}
\setbeamertemplate{itemize subitem}{$\color{beamer@simple@color}\bullet$}
\setbeamertemplate{enumerate items}[square]
\setbeamertemplate{section in toc}[sections numbered]
\setbeamertemplate{subsection in toc}[square]



% color definition
\definecolor{mygrey}{rgb}{0.52, 0.52, 0.51}

\setbeamercolor{structure}{fg=beamer@simple@color, bg=mygrey!10!white}
\setbeamercolor{frametitle}{fg=beamer@simple@color, bg=white}
\setbeamercolor{block title}{fg=beamer@simple@color,bg=white}
\setbeamercolor{block body}{fg=black,bg=white}
\setbeamercolor{block body alerted}{bg=white}
\setbeamercolor{block title alerted}{fg=beamer@simple@color,bg=white}
\setbeamercolor{alerted text}{fg=beamer@simple@color}
\setbeamerfont{block title alerted}{series=\mdseries}
\setbeamerfont{alerted text}{series=\bfseries\boldmath}
\hypersetup{colorlinks=true,linkcolor=,citecolor=Green,urlcolor=oliver}
% \usefonttheme[onlymath]{serif}
\setbeamerfont{frametitle}{series=\bfseries\boldmath}
\setbeamerfont{block title}{series=\bfseries\boldmath}
\setbeamerfont{title}{series=\bfseries\boldmath}
\setbeamertemplate{frametitle}{\vskip2pt\hskip-6pt\underbar{\insertframetitle}} % add line under frametitle

% theorem env
\setbeamertemplate{theorem begin}{%
{
  \vspace{5pt}%
  \usebeamerfont*{block title}%
  \selectfont%
  \usebeamercolor[fg]{block title}%
  \textbf{%
  \inserttheoremname
  \inserttheoremnumber
  \ifx \inserttheoremaddition \empty \else\ [\inserttheoremaddition]\fi
  }
}
}
\setbeamertemplate{theorem end}{\vspace{5pt}}
% proof env
\setbeamertemplate{proof begin}{%
{\vspace{5pt}
\usebeamercolor[fg]{block title}
\textit{\textbf{Proof:}}}
}
\setbeamertemplate{proof end}{
\qedhere
\vspace{5pt}
}

% more theorem env
\newtheorem{conjecture}[theorem]{Conjecture}
\newtheorem{observation}[theorem]{Observation}
\newtheorem{question}[theorem]{Question}


% ----------------------------------------------------------------------
%  Simple math stuff
% ----------------------------------------------------------------------
\renewcommand{\subset}{\subseteq}
% ---- SYMBOLS ----
\let\e\varepsilon               % a ``real'' epsilon — better yet, just use Unicode ε.
%
%  I give up.  These are in the wrong font, but my kludged versions 
%  LOOK like kludges, especially \Z, \Q, and \C.
%
\def\Real{ℝ}
\def\Proj{ℙ}
\def\Hyper{ℍ}
\def\Integer{ℤ}
\def\Natural{ℕ}
\def\Complex{ℂ}
\def\Rational{ℚ}

\let\N\Natural
\let\Q\Rational
\let\R\Real
\let\Z\Integer
\def\Rd{\Real^d}
\def\RP{\Real\Proj}
\def\CP{\Complex\Proj}



% ---- OPERATORS (requires amsmath) ----
\def\aff{\operatorname{aff}}        
\def\area{\operatorname{area}}
\def\argmax{\operatornamewithlimits{arg\,max}}
\def\argmin{\operatornamewithlimits{arg\,min}}
\def\Aut{\operatorname{Aut}}        % Automorphism group
\def\card{\operatorname{card}}  % cardinality, deprecated for \abs
\def\conv{\operatorname{conv}}  
\def\E{\operatorname{E}}            % Expectation: $\E[X]$ (like \Pr)
\def\EE{\operatornamewithlimits{E}}
\def\Hom{\operatorname{Hom}}        % Homomorphism group
\def\id{\operatorname{id}}      % identity
\def\im{\operatorname{im}}      % image
\def\lcm{\operatorname{lcm}}
\def\lfs{\operatorname{lfs}}        % local feature size
\def\poly{\operatorname{poly}}
\def\polylog{\operatorname{polylog}}
\def\rank{\operatorname{rank}}
\def\rel{\operatorname{rel\,}}  % relative (interior, boundary, etc.)
\def\sgn{\operatorname{sgn}}
\def\vol{\operatorname{vol}}        % volume

\def\fp#1{^{\underline{#1}}}        % falling powers: $n\fp{d}$
\def\rp#1{^{\overline{#1}}}     % rising powers:  $n\rp{d}$

\def\setsymdiff{\operatorname{\triangle}}
% % --- Darts and fences ---
% % less nice replacements for stmaryrd characters
% \@ifundefined{shortrightarrow}{\let\shortrightarrow\rightarrow}{}
% \@ifundefined{shortleftarrow}{\let\shortleftarrow\leftarrow}{}
% \@ifundefined{shortuparrow}{\let\shortuparrow\uparrow}{}
% \@ifundefined{shortdownarrow}{\let\shortdownarrow\downarrow}{}

\def\arcto{\mathord\shortrightarrow}
\def\arcfrom{\mathord\shortleftarrow}
\def\arc#1#2{#1\arcto#2}
\def\cra#1#2{#1\mathord\shortleftarrow#2}
\def\fence#1#2{#1\mathord\shortuparrow#2}
\def\ecnef#1#2{#1\mathord\shortdownarrow#2}

% --- Cheap displaystyle operators ---
\def\Frac#1#2{{\displaystyle\frac{#1}{#2}}}
\def\Sum{\sum\limits}
\def\Prod{\prod\limits}
\def\Union{\bigcup\limits}
\def\Inter{\bigcap\limits}
\def\Lor{\bigvee\limits}
\def\Land{\bigwedge\limits}
\def\Lim{\lim\limits}
\def\Max{\max\limits}
\def\Min{\min\limits}

% ---- RELATORS ----
\def\deq{\stackrel{\scriptscriptstyle\triangle}{=}} % Use := instead.
\def\into{\DOTSB\hookrightarrow}        % = one-to-one
\def\onto{\DOTSB\twoheadrightarrow}
\def\inonto{\DOTSB\lhook\joinrel\twoheadrightarrow}
\def\from{\leftarrow}
\def\tofrom{\leftrightarrow}
\def\mapsfrom{\mathrel{\reflectbox{$\mapsto$}}}
\def\longmapsfrom{\mathrel{\reflectbox{$\longmapsto$}}}

% ---- DELIMITER PAIRS ----
% --- always self-scaling delmiter pairs ---
\def\set#1{\left\{ #1 \right\}}
\def\floor#1{\left\lfloor #1 \right\rfloor}
\def\ceil#1{\left\lceil #1 \right\rceil}
\def\seq#1{\left\langle #1 \right\rangle}
\def\abs#1{\left| #1 \right|}
\def\norm#1{\left\| #1 \right\|}
\def\paren#1{\left( #1 \right)}     % need better macro name!
\def\brack#1{\left[ #1 \right]}     % need better macro name!
\def\indic#1{\left[ #1 \right]}     % indicator variable; Iverson notation