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!