\documentclass{standalone}
\usepackage[en]{superfig}
\sfsetrole{x}{sfTeal}
\begin{document}\begin{tikzpicture}
\sftopformula{F}{$x$}
\sfrow{R1}{10mm}
  \sfnode[role=x]{A}{A}{8mm}{8mm}
\sfrowend
\end{tikzpicture}\end{document}