\documentclass[landscape]{foils}

\usepackage{fixseminar}
\usepackage[display]{texpower}

\begin{document}

\title{The \code{texpower} / {\normalfont \texttt{foils} Demo}}
\author{Stephan Lehmke\\\code{mailto:Stephan.Lehmke@cs.uni-dortmund.de}}
\maketitle

\foilhead{A list environment}

\pause

\stepwise
{
  \begin{description}
  \item[foo.] \step{bar.}
  \step{\item[baz.]} \step{qux.}
  \end{description}
  }

\foilhead{An aligned equation}

\pause

\parstepwise
{
\begin{eqnarray}
\sum_{i=1}^{n} i & \step{=} & \restep{1 + 2 + \cdots + (n-1) + n}\\
     & \step{=} & \restep{1 + n + 2 + (n-1) + \cdots}\\
     & \step{=} & \restep
     {
      \switch
      {
       \vphantom{\underbrace{(1 + n) + 
       \cdots + (1 + n)}_{\times\frac{n}{2}}}%
       (1 + n) + \cdots + (1 + n)%
      }
      {\underbrace{(1 + n) + \cdots + (1 + n)}_{\times\frac{n}{2}}}%
      }
      \\
      & \step{=} & \restep{\frac{(1 + n)\step{{}\cdot n}}{\restep{2}}}
  \end{eqnarray}
}

\end{document}