如何縮小心智圖中根概念與一級概念之間的距離

Question

我想縮短根概念和一級概念之間的距離。我能做些什麼？謝謝。

\documentclass[border=2pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{mindmap}%,backgrounds
\begin{document}
\tikzstyle{root concept}+=[concept color=blue!20,minimum size=2cm,font=\sffamily\huge]
\tikzstyle{level 1 concept}+=[sibling angle=60,font=\sffamily\large]
\begin{tikzpicture}[mindmap]
\node [concept] (n1) {scale}
    child[concept color=red,grow=30] {node[concept] (c1) {bad}}
    child[concept color=orange,grow=90] {node[concept] (c2) {worse}}
    child[concept color=green,grow=150] {node[concept] (c3) {worst}}
    child[concept color=lime,grow=210] {node[concept] (c4) {good}}
    child[concept color=blue!50,grow=-30] {node[concept] (c5) {better}}
    child[concept color=pink,grow=-90] {node[concept] (c6) {best}};
\end{tikzpicture}

\end{document} 

當我設定水平距離= 3.5cm時