+\overlays{2}{
+\begin{slide}{rough discretization}
+ \begin{itemstep}
+ \item example: homogenous field of force $\vec{F} = (0,-mg)$ \\
+ \begin{tabular}{ll}
+ equation of motion: & $\vec{F} = m \vec{a} = m \frac{d^2 \vec{r}}{dt^2}$ \\
+ initial condition: & $\vec{r}(t=0) = \vec{r_0} = (x_0,y_0)$ \\
+ & $\frac{d \vec{r}}{dt}|_{t=0} = (v_{x_0},v_{y_0})$ \\
+ \end{tabular}
+ \item algorithm using discretized time ($T_{total} = N \tau$):
+ \begin{tabular}{lll}
+ $x^1 = x_0;$ & $y^1 = y_0;$ & \\
+ $v^1_x = v_{x_0};$ & $v^1_y = v_{y_0};$ & \\
+ loop: & $x^2 = x^1 + \tau v^1_x;$ & $y^2 = y^1 + \tau v^1_y;$ \\
+ & $v^2_x = v^1_x;$ & $v^2_y = v^1_y + (-mg) \tau;$ \\
+ & $x^1 = x^2;$ & $y^1 = y^2$ \\
+ & $v^1_x = v^2_x;$ & $v^1_y = v^2_y;$ \\
+ \end{tabular}
+ \end{itemstep}
+\end{slide}}
+
+%\overlays{3}{
+%\begin{slide}{}
+% \begin{itemstep}
+% \item
+% \item
+% \item
+% \end{itemstep}
+%\end{slide}}
+
+%\overlays{3}{
+%\begin{slide}{}
+% \begin{itemstep}
+% \item
+% \item
+% \item
+% \end{itemstep}
+%\end{slide}}
+
+%\overlays{3}{
+%\begin{slide}{}
+% \begin{itemstep}
+% \item
+% \item
+% \item
+% \end{itemstep}
+%\end{slide}}
+
+%\overlays{3}{
+%\begin{slide}{}
+% \begin{itemstep}
+% \item
+% \item
+% \item
+% \end{itemstep}
+%\end{slide}}
+
+%\overlays{3}{
+%\begin{slide}{}
+% \begin{itemstep}
+% \item
+% \item
+% \item
+% \end{itemstep}
+%\end{slide}}
+
+%\overlays{3}{
+%\begin{slide}{}
+% \begin{itemstep}
+% \item
+% \item
+% \item
+% \end{itemstep}
+%\end{slide}}
+
+%\overlays{3}{
+%\begin{slide}{}
+% \begin{itemstep}
+% \item
+% \item
+% \item
+% \end{itemstep}
+%\end{slide}}
+
+%\overlays{3}{
+%\begin{slide}{}
+% \begin{itemstep}
+% \item
+% \item
+% \item
+% \end{itemstep}
+%\end{slide}}
+
+%\overlays{3}{
+%\begin{slide}{}
+% \begin{itemstep}
+% \item
+% \item
+% \item
+% \end{itemstep}
+%\end{slide}}
+
+%\overlays{3}{
+%\begin{slide}{}
+% \begin{itemstep}
+% \item
+% \item
+% \item
+% \end{itemstep}
+%\end{slide}}
+