further explain updated sketch

doc/chapter/3ui.tex

@@ -43,7 +43,9 @@ Note that since the application is still under construction, so not all screensh
     \includegraphics[width=\linewidth]{img/skizze}
     \caption[First sketch of the planned layout]{A first sketch of the planned layout, created with Microsoft Paint.
     The buttons are (first row, from left to right): step over, step into, step out, run, pause, debug; and (second row, from left to right): step back, step back out, run backwards.
-    The actions corresponding to the buttons will be the same as described for the keyboard input in table~\ref{table:keys}, at least for the features that are already implemented.}
+    The actions corresponding to the buttons are the same as described for the keyboard input in table~\ref{table:keys}, at least for the features that are already implemented.
+    The left four rectangles show the progress of the four extremal layouts.
+    The right rectangle shows pseudocode of the algorithm and the position of the current step.}
     \label{fig:sketch}
 \end{figure}