  In the seminal paper [Arch. Ration. Mech. Anal. 176 (2005), 351--361],
  Savin proved the $C^1$-regularity of planar $\infty$-harmonic functions $u$.
Here we give a new understanding of it from a capacity viewpoint and drop
several high technique arguments therein. Our argument is essentially based on
a topological lemma of Savin, a flat estimate by Evans and Smart, %
\cite{es11a},
  $W^{1,2}_{loc}$-regularity of $|Du|$ and Crandall's flow for infinity
harmonic functions.
