I would like to have array with square cells and fill cells with colors. There is done implementation of table with square cells by W. Robertson http://www.tug.org/pracjourn/2005-2/robertson/robertson.pdf :
\newlength\celldim \newlength\fontheight \newlength\extraheight
\newcounter{sqcolumns}
\newcolumntype{S}{ @{}
>{\centering \rule[-0.5\extraheight]{0pt}{\fontheight + \extraheight}}
p{\celldim} @{} }
\newcolumntype{Z}{ @{} >{\centering} p{\celldim} @{} }
\newenvironment{squarecells}[1]
{\setlength\celldim{2em}%
\settoheight\fontheight{A}%
\setlength\extraheight{\celldim - \fontheight}%
\setcounter{sqcolumns}{#1 - 1}%
\begin{tabular}{|S|*{\value{sqcolumns}}{Z|}}\hline}
% squarecells tabular goes here
{\end{tabular}}
\newcommand\nl{\tabularnewline\hline}
So I write:
\documentclass[a4paper,12pt]{report}
\usepackage[MeX]{polski}
\usepackage[utf8]{inputenc}
\usepackage[table]{xcolor}
\usepackage{array}
\usepackage{calc}
\newlength\celldim \newlength\fontheight \newlength\extraheight
\newcounter{sqcolumns}
\newcolumntype{S}{ @{}
>{\centering \rule[-0.5\extraheight]{0pt}{\fontheight + \extraheight}}
p{\celldim} @{} }
\newcolumntype{Z}{ @{} >{\centering} p{\celldim} @{} }
\newenvironment{squarecells}[1]
{\setlength\celldim{4em}%
\settoheight\fontheight{A}%
\setlength\extraheight{\celldim - \fontheight}%
\setcounter{sqcolumns}{#1 - 1}%
\begin{tabular}{|S|*{\value{sqcolumns}}{Z|}}\hline}
% squarecells tabular goes here
{\end{tabular}}
\newcommand\nl{\tabularnewline\hline}
\begin{document}
\begin{squarecells}{4}
\cellcolor{red}16 & 3 & 2 & 13 \nl
5 & 10 & 11 & 8 \nl
9 & 6 + 2 & 7 & 12 \nl
4 & 15 & 14 & 1 \nl
\end{squarecells}
\end{document}
Output is:

Cell is filled with red color a little more than it should be. Question is, how to properly fill cell with color? Or maybe is there some other good solution to create table with square cells?

