What packages can help me make the following style of slides?

Question

Consider the image below It looks great for presentation.

My question is what TeX packages render such slides?

Answer 1

That may be achieved via different methods, I am sending here one idea of how to do it.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\documentclass[aspectratio=169]{beamer}
\usetheme{Madrid} \usecolortheme{fly}
\setbeamercolor{normal text}{fg=white}
\setbeamercolor{frametitle}{fg=red!40}
\setbeamertemplate{navigation symbols}{} % Remove nav. icons
\usepackage{graphicx}
\usebackgroundtemplate
{\includegraphics[width=\paperwidth,height=\paperheight]{background-board.png}}
\usepackage{ulem,xcolor}
\makeatletter
    \newcommand{\coloruuline}[2]{%
        \UL@protected\def\temp@uuline{\leavevmode \bgroup
            \UL@setULdepth
            \ifx\UL@on\UL@onin \advance\ULdepth2.8\p@\fi
            \markoverwith{\textcolor{#1}{\lower\ULdepth\hbox
                {\kern-.03em\vbox{\hrule width.2em\kern1\p@\hrule}\kern-.03em}}}%
        \ULon}%
        \temp@uuline{#2}%
    }

\makeatother
\newcommand{\rul}[1]{\coloruuline{red!40}{#1}}
\title[Example]{Beamer example}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{document}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\section{First section}
\begin{frame}[plain]{The ergotic theorem}
\rul{Theorem} (Von Neumann's Ergodic Theorem)
Let $(X, \mathcal{X}, \mu, T)$ be a measure preserving system and $f \in L^{2}(\mu)$. Then
\begin{equation}
 \lim {n \rightarrow \infty} \frac{1}{n} \sum{i=0}^{n-1} f \circ T^{i} \rightarrow \mathbb{E}(f \mid \mathcal{I}(T))

\end{equation}
\vspace{10pt}
\rul{Theorem} (Weak version)
Let $(X, \mathcal{X}, \mu, T)$ be a measure preserving system and $A \in \mathcal{X}, \mu(A)>0 .$ Then
\begin{equation}
 \lim _{n \rightarrow \infty} \mu\left(A \cap T^{-n} A\right) \geq \mu(A)^{2}

\end{equation}
\end{frame}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\end{document}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% EOF

Sample of the output.

The background picture.

Answer 2

How about this? I created a new environment for that. I think everything should be described inline.

\documentclass{beamer}
\usetheme{default}
\def\myEmphColor{red}% <== ADAPT COLOR HERE.
\usepackage{amsmath,ulem,ifthen}
\setbeamercolor{frametitle}{fg=\myEmphColor}
\usebackgroundtemplate{\includegraphics[width=\paperwidth,height=\paperheight]{example-image-duck}}% Simply use a blackboard-image of correct size here. Sorry for stretching you, Mr. Duck!
\newenvironment{mythm}[1][]{% create new environment with 1 optional parameter.
      \setbeamercolor{block title}{fg=black}%
      \setbeamercolor{block body}{fg=black}%
      \begin{block}{{%
         \color{\myEmphColor}\uuline{\color{black}Theorem}}% print 'Theorem' and underline it twice in color 'myEmphColor'.
         \ifthenelse{\equal{#1}{}}{}{ (#1)}}% if given, add the optional theorem name in parentheses.
   }{%
      \end{block}%
   }
\begin{document}

   \begin{frame}{The ergodic theorem}
      \begin{mythm}[Von Neumann's Ergodic Theorem]
         Let $(X,\mathcal X,\mu,T)$ be a measure preserving system and $f\in L^2(\mu)$. Then
         \begin{equation}
            \lim_{n\to\infty}\frac{1}{n}\sum_{i=0}^{n-1}f\circ T^i\to\mathbb E(f\vert\mathcal I(T)).
         \end{equation}
      \end{mythm}
  \begin{mythm}% &lt;- works without theorem title, too.
     Let $(X,\mathcal X,\mu,T)$ be a measure preserving system and $A\in\mathcal X$, $\mu(A)&gt;0$. Then
     \begin{equation*}
        \lim_{n\to\infty}\mu(A\cap T^{-n}A)\geq\mu(A)^2.
     \end{equation*}
  \end{mythm}

\end{frame}
\end{document}