# How specify tree levels nodes sizes?

I am working on a TikZ tree following the tutorial called A Lecture Map for Johannes from the TikZ manual. I am having trouble to get nodes from deeper level smaller than ones of previous level. I am not able to modify the following example to get this effect that seems to be done by default according to the documentation (because nothing is mentioned to do that).

In the following example, with TexLive 2012/Debian, all the levels have the same size (even for the ones with smaller font). How should I change that ?

% Models of conurrency as a treewing the
\documentclass{standalone}

\usepackage{tikz}
\usetikzlibrary{trees}
\usetikzlibrary{mindmap}

\begin{document}

\begin{tikzpicture} [
mindmap,
every node/.style={concept, circular drop shadow, execute at begin node=\hskip0pt},
root concept/.append style={color=black, fill=white, line width=1ex, text=black},
shared concept/.append style={concept color=green!60!black},
%text width=2.5cm,
text=white,
grow cyclic,
align=flush center,
level 1/.style={level distance=5.5cm, sibling angle=90},
level 2/.style={level distance=5.5cm, sibling angle=55, font=\small}]
]
\node[root concept, font=\bfseries] {Concurrency Programming Models}
child [shared concept] { node {Shared State}
child { node {Lock based}}
child { node {Transaction based}}
}
child [concept color=orange]{ node {Message Passing}
child { node {Asynchronous}}
child { node {Synchronous}}
}
child [concept color=purple] { node {Functional Reactive Programming}
}
child [concept color=blue!80!black] { node {Declarative Concurrency}
} ;

\end{tikzpicture}

\end{document}
-
One idea could be apply How to decrease the size of single node in mindmap? to an entire level x. –  Claudio Fiandrino Feb 4 '13 at 14:49