TikZ change coordinate system so Y points downwards

Question

How can I change the default coordinate system of TikZ, so the Y coordinates go downwards, instead of upwards. This is because in the picture I'm trying to draw it is more natural to reference points this way.

I was trying to use negative values in the declaration, but some drawing commands don't really like it, like the grid, where horizontal lines simply don't get drawn this way:

\begin{tikzpicture}[x=1cm,y=-1cm]
\draw (0, 0) grid (7, 7);
\end{tikzpicture}

Result:

Answer 1

You could use yscale=-1:

\documentclass{article}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}[yscale=-1]
\draw (0, 0) grid (7, 7);
\node at (7,7) {A};
\end{tikzpicture}

\end{document}