This month’s puzzle was a callback to not one but two older website puzzles. The first Hall of Mirrors puzzle focused on the idea of bouncing a ray of light off a series of mirrors placed inside a grid. As many solvers found, it was possible to have a ray of light reflecting across a series of mirrors, with both ends hitting perpendicular (and just off-center) mirrors.

But what to do next? Well, similar to another puzzle from the vault, Crosswords, the ultimate goal was to find a message within a completed picture, and to do so without any other help or instructions.

And so for this grid: the path of light passes through each of the sixteen white 3-by-3 regions, through their centers, and at angles that are multiples of π/8. This corresponds to flag semaphore lettering. (Weakly alluded to by the yellow and red coloring of the boundary cells.) When translated, and noting the extra orange segment (above) is an apostrophe, not a mirror, we get the answer to this month’s puzzle, SEASON’S GREETINGS.