% Glider, a hacker emblem (http://www.catb.org/hacker-emblem/)
% Author: Alex Hirzel
% License: Public Domain
\documentclass[border=1mm]{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[thick]
\draw (0,0) grid (3,3);
\foreach \c in {(0,0), (1,0), (2,0), (2,1), (1,2)}
    \fill \c + (0.5,0.5) circle (0.42);
\end{tikzpicture}
\end{document}

