\begin{tikzpicture}
    \begin{scope}
        \filldraw[fill=matblue, thick, fill opacity=0.8, draw=black] (0,0) rectangle (5,3);
    \end{scope}

    \begin{scope}
        \filldraw[thick, fill=matbrown] (0,0) rectangle (5,1);
        \draw[thin] (0,0) grid (5,3);
    \end{scope}

    \begin{scope}
        \filldraw[thick, fill=matgray] (2.5,1.25) circle (.25);
    \end{scope}
\end{tikzpicture}
