How to change the shape of TikZ's mindmap children?

Question

Consider the original example of tikz's mindmap. The standard shape of both parent and children is circle. The official document states the difference of TikZ's mindmap from standard mindmaps by using perfect circles. I have some questions for basic customization:

Question 1: How to change the shape of concepts to form ellipse or rectangular?

Question 2: How to make the child flexible for long text? In standard mode, if having a long text, the circle will grow up (but without shift) to cover the whole mindmap.

Answer 1

You can modify the attributes used for concepts using every concept (to affect all the concepts) root concept (to affect only the root concept), and level 1 concept, level 2 concept, ... , level 4 concept (to affect concepts on a per level basis).

If you are going to change the concept shape, (to a rectangular shape, for example), then probably you will also have to change the style for the connection bar used. A little example:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{mindmap,decorations.pathmorphing}
\usepackage{lipsum}

\begin{document}

\tikzstyle{circle connection bar}=[to path={
  [every circle connection bar]
  decorate [decoration={snake}]
  { -- (\tikztotarget) \tikztonodes}
},
append after command={[fill=olive,draw=olive]}
]
\begin{tikzpicture}[mindmap,
  every concept/.style={rectangle,draw=olive,fill=olive!20,inner sep=8pt}]
\node [concept,text width=4cm] {\lipsum[2]}
child[grow=30] {node[concept] {child}}
child[grow=0 ] {node[concept] {child}}
child[grow=-30] {node[concept] {child}};
\end{tikzpicture}

\end{document}