\documentclass[a4paper,landscape]{foils}
\usepackage[utf8]{inputenc}
\usepackage{amssymb}
\usepackage[svgnames]{xcolor}
\usepackage{graphicx}
\usepackage{isabelle,isabellesym}
\usepackage{pdfsetup}
\makeatletter
%colors
\newcommand{\titlestyle}{\color{DarkGreen}}
\newcommand{\hilitecolor}{\color{Blue}}
\newcommand{\hilite}[1]{{\hilitecolor#1}}
\newcommand{\red}[1]{{\color{Red}#1}}
\newcommand{\green}[1]{{\color{DarkGreen}#1}}
%headings
\renewcommand{\isamarkupchapter}[1]{\newpage\thispagestyle{empty}\MyLogo{\let\\=\relax #1}\vspace*{0.4\textheight}\begin{center}\LARGE\bf\color{DarkGreen} #1\end{center}}
\renewcommand{\isamarkupsection}[1]{\foilhead{\color{DarkGreen}#1}}
\renewcommand\isamarkupparagraph{\@startsection{paragraph}{4}{0pt}{\bigskipamount}{0.5ex \@plus .1ex}{\normalsize\bf\color{DarkBlue}}}
%item spacing
\renewcommand\@listIa{\leftmargin\leftmargini
\topsep 0\p@ \@plus 0.5\p@ \@minus 1\p@
\parsep 2\p@ \@plus 1\p@ \@minus 1\p@
\itemsep 2\p@ \@plus 1\p@ \@minus 0.5\p@}
\makeatother
\parindent 0pt\parskip 0.5ex
\urlstyle{sf}
\isabellestyle{it}
\MyLogo{}
\newcommand{\plainstyle}{\normalsize\sf\color{black}}
\renewcommand{\isastyletext}{\normalsize\sf}
\renewcommand{\isastyletxt}{\sf}
\renewcommand{\isastylecmt}{\sf}
\isadroptag{theory}
\isafoldtag{proof}
\begin{document}
\title{\titlestyle Simple slides with with FoilTeX}
\author{Makarius Wenzel, Augsburg \\ \url{https://sketis.net}}
\date{}
\maketitle
\vfill
\begin{center}
\includegraphics[width=0.15\textwidth]{isabelle_logo}
\end{center}
\vfill
\input{session}
\end{document}