Listen With Others

The object of the puzzle was to enable solvers to produce a RUBIN VASE optical illusion in the grid.

The Rubin vase is probably the best-known illusion of the type called Figure and Ground where the brain can either see the vase or the faces but not both at the same time – hence the title – One or the Other. It is worth noting that there is no dictionary or common reference book that includes the phrase Rubin Vase whereas there are many on-line references and examples from different sources.

The idea seemed to lend itself to a Right and Left puzzle with mirror symmetry. The clues needed a device(s) indicating where the boundary lines of the faces/vase are to be drawn. To show their understanding of the theme, solvers should indicate RUBIN VASE in some way.

The first outline grid, had RUBY (which can be changed to RUBIN) VASE, lying within the area of the grid that would become the vase, BLACK FACES, lying within the areas that would become the faces, plus FIGURE and GROUND and a thematically appropriate word at 1 across.

The bottom third of the grid is linked to the middle third only through two entries which is not good.

Indicating the line on one side of the grid only and having a message from clues saying DRAW MIRROR IMAGE would enable the illusion to appear. The methods used to indicate the line coordinates and the message had to avoid making difficult to write double-clues even more difficult to write and solve; effectively this meant ONE device per double-clue. Therefore, there would be only nine letters available to indicate points on the line, hence talking heads rather than closed mouths. The number of rows meant lips were never going to be possible.

The second grid on the left is one example of an initially filled grid with lines drawn.

Solvers would colour the two faces black and the vase ruby red, finally, changing the Y of RUBY to IN forming RUBIN (which fortuitously also means ruby red).

WHITE FACES was also a possibility instead of BLACK FACES. This option would stop solvers worrying about obliterating letters when using black.

The correct route to draw the face-line needed to be unambiguous, ideally spelling a thematic word or message.

In this example the linkage in the lower half of the grid is poor and many letters in PAEDAGOGUE would be unindicated. So, other grids were produced to put more unches in 1 across, get rid of the 3-letter entries, improve the average entry length and limit the number of un-indicated letters in an entry to one or two whilst abiding by standard unching rules.

The published grid was a compromise to minimise obscure words and improve connectivity. Unfortunately, that meant the letters for the face-line did not spell anything and required a hint to be added to the preamble.

The puzzle was a collaboration. Hurón is Spanish for Ferret and contains the letters URON from Tiburon. The name was suggested by Mash, one of the test solvers, as a replacement for Tibet, the name we were going to use.