🚀 go-pugleaf

I want my titles centered with now numbering, which I can do with

\renewcommand{\thesection}{}
\renewcommand{\thesubsection}    { }
\renewcommand{\thesubsubsection} { }

\def\section{\@startsection{section}{1}{\z@}{-3.5ex plus-1ex minus
    -.2ex}{2.3ex plus.2ex}{\centering\reset@font\normalsize\bf\sc}}
\def\subsection{\@startsection{subsection}{2}{\z@}{-3.25ex plus-1ex
    minus-.2ex}{1.5ex plus.2ex}{\centering\reset@font\normalsize\it}}
\def\subsubsection{\@startsection{subsubsection}{3}{\z@}{-3.25ex plus
 -1ex minus-.2ex}{1.5ex plus.2ex}{\centering\reset@font\normalsize}}

(startsection is defined in latex.ltx).
But in the appendix I would like to have 'Appendix A' in the first line
and the title itself on the second line, all centered. Is it possible just
to modify the above command? Such like
 
\renewcommand{\appendix}{\par
  \setcounter{section}{0}%
  \setcounter{subsection}{0}%
  \renewcommand{\thesection}{Appendix \Alph{section}} }

which adds the numbering 'Appendix A', but on the same line as the title itself.
I tried inserting the \newline command, but that didn't work. Any other
(maybe TeX) command that could do this easily?

Thanks for any help, Christian.

-- 
Christian Jost, Paris, France
jost@psisun.u-psud.fr