Dan proposed the following solution to Puzzle 205 in [comment #11](https://forum.azimuthproject.org/discussion/comment/20339/#Comment_20339)

>\[
\Psi(x, y) =
\begin{cases}
\texttt{false} & \mbox{if } (x = 1 \mbox{ and } y \le 2) \mbox{ or } (x = 2 \mbox{ and } y \le 4) \\\\
\texttt{true} & \mbox{otherwise.}
\end{cases}
\]

>


Nice picture! That's a good way to visualize what's going on. As you say, the monotonicity becomes visible.

I think Michael's suggested correction is right:

>\[
\Psi(x, y) =
\begin{cases}
\texttt{false} & \mbox{if } (x = 1 \mbox{ and } y \lt 2) \mbox{ or } (x = 2 \mbox{ and } y \lt 4) \\\\
\texttt{true} & \mbox{otherwise.}
\end{cases}
\]

but luckily, this doesn't affect the picture!