Automatic numbering of nested environments / items

Question

I would like to have an environment, let's call it nested, which produces output like

Case 1: top level item 1
Case 2: top level item 2
Case 2.1: nested item 1
Case 2.2: nested item 2
Case 2.2.1: even nestier item 1
Case 2.3: just nested again
Case 3: and toplevel to top it off

from code that either looks like nested enumerate's, i.e.

\begin{nested}
\item top level item 1
\item top level item 2
      \begin{nested}
      \item nested item 1
      \item nested item 2
            \begin{nested}
            \item even nestier item 1
            \end{nested}
      \item just nested again
      \end{nested}
\item and toplevel to top it off
\end{nested}

or from code that looks, well, like nested environments:

\begin{nested} top level item 1 \end{nested}
\begin{nested} top level item 2 
    \begin{nested} nested item 1 \end{nested}
    \begin{nested} nested item 2 
            \begin{nested} even nestier item 1 \end{nested}
    \end{nested}
    \begin{nested} just nested again \end{nested}
\end{nested}
\begin{nested} and toplevel to top it off \end{nested}

In fact, I don't much care how the code has to look at all, as long as the numbering on the cases is done automatically. I tried to implement both of the above, however, and I could not figure it out at all. Is there a way to achieve this?

Answer 1

\documentclass{scrartcl}
\usepackage{enumitem}
\SetLabelAlign{Case}{Case #1:\hfil}
\newlist{nested}{enumerate}{5}
\setlist[nested]{nosep,leftmargin=0pt,labelwidth=*,align=Case,label*=.\arabic*}
\setlist[nested,1]{label=\arabic*}

\begin{document}
\begin{nested}
\item top level item 1
\item top level item 2
      \begin{nested}
      \item nested item 1
      \item nested item 2
            \begin{nested}
            \item even nestier item 1
            \end{nested}
      \item just nested again
      \end{nested}
\item and toplevel to top it off
\end{nested}


\end{document}