Cafe wall

Optical illusions, 4/5

\documentclass[tikz,border=10pt]{standalone}
\newcommand{\cafestrip}[1][]{%
  \foreach \a in {1,...,6}
    {\draw[gray,very thick,fill=black,#1] (2*\a-1,0) rectangle(2*\a,1)  ;
     \draw[gray,very thick,fill=white,#1] (2*\a,0)   rectangle(2*\a+1,1);}
}
\begin{document}
\begin{tikzpicture}
%% the horizontal lines appear to slope
  \foreach \b/\c in {1/0,2/3,3/0,4/-3,5/0,6/3}
    \cafestrip[xshift=\c mm,yshift=\b cm];
\end{tikzpicture}
\end{document}