Simplifying multiple \foreach loops
Find the pattern, and use nested loops.
\documentclass{beamer}
\beamertemplatenavigationsymbolsempty
\usepackage{tikz}
\begin{document}
\begin{frame}[t]
\frametitle{Spiro using loop}
\vskip -.6cm
\begin{tikzpicture}
\foreach \i in {0,.2,.4,...,1.8} {
\pgfmathsetmacro\firstcolor{scalar(100-\i*50)}
\pgfmathsetmacro\secondcolor{scalar(90-\i*50)}
\begin{scope}[scale=2]
\draw [
line width=.2cm,color/.expanded=blue!\firstcolor!white,
fill/.expanded=blue!\secondcolor!white, looseness=1
] (0,-2.2+\i) foreach \X in {0,90,180,270} {
[rotate=\X] -- (0,-2.2+\i) to [out=0,in=-120] ++ (0.2,0.1) to
[out=60,in=-150] ++ (1.9-\i,1.9-\i) to [out=30,in=-90] ++ (0.1,0.2)
} -- cycle;
\end{scope}
}
\end{tikzpicture}
\end{frame}
\end{document}
You can get this effect also with scale. It does not match your picture precisely, but that's on purpose because I think the arcs of the effective corners are also to be scaled.
\documentclass{beamer}
\beamertemplatenavigationsymbolsempty
\usepackage{tikz}
\begin{document}
\begin{frame}[t]
\frametitle{Spirifankerln}
\begin{tikzpicture}[pics/spiro/.style={code={
\draw[line width=.1cm,looseness=1,pic actions]
(0,-2) foreach \X in {0,90,180,270}
{[rotate=\X] -- (0,-2) to[out=0,in=-120] ++ (0.2,0.1) to[out=60,in=-150] ++ (1.7,1.7)
to[out=30,in=-90] ++ (0.1,0.2)} -- cycle;}}]
\foreach \X in {100,90,...,0}
{\pic[draw=blue!\X,fill=blue!\X,scale={1.8*(\X+10)/100}]{spiro};}
\end{tikzpicture}
\end{frame}
\end{document}