tex print square

square.tex

\documentclass{article}
\usepackage{xcolor}
\begin{document}
    {\centering
    \count2=10\def\content{O}
    \count0=0\loop\ifnum\count0<\count2{
        \count1=0\loop \ifnum\count1<\the\numexpr \count2-\count0 {
        {\color{white}\content}
        }\advance\count1 by 1\repeat
        \count1=0\loop \ifnum\count1<\the\numexpr 2*\count0-1{
        \content
        }\advance\count1 by 1\repeat
        \count1=0\loop \ifnum\count1<\the\numexpr \count2-\count0 {
        {\color{white}\content}
        }\advance\count1 by 1\repeat
    
    }\advance\count0 by 1\repeat
        \count0=\count2\loop\ifnum\count0>0{
        \count1=0\loop \ifnum\count1<\the\numexpr \count2-\count0 {
        {\color{white}\content}
        }\advance\count1 by 1\repeat
        \count1=0\loop \ifnum\count1<\the\numexpr 2*\count0-1{
        \content
        }\advance\count1 by 1\repeat
        \count1=0\loop \ifnum\count1<\the\numexpr \count2-\count0 {
        {\color{white}\content}
        }\advance\count1 by 1\repeat
        
    }\advance\count0 by -1\repeat
    }
\end{document}