(Incidentally, Shenk confirmed to me in an e-mail that the only reason he went with the obscure ST. CLAIR AVENUE is that he'd overlooked VENTNOR AVENUE—a rare miss for a legend like him, akin to Ozzie Smith booting a routine grounder. If not for this freak slip, then all five of our theme entries would have been identical.)
Why were the theme entries in the exact same places in the grid? Primarily because American crosswords exhibit something called "180-degree rotational symmetry." In other words, if you turn the grid upside down, the pattern of black squares will look the same as it does right-side up. This requires puzzle designers to offset each theme entry with a same-length entry, a constraint that largely locks in the shape of your grid once you've got your longer clues down.
In our RAVEN grids, you'll notice that the 10-letter entries CONTRAVENE and COBRA VENOM offset each other, as do BRAVE NEW WORLD and the 13-letter AVENUE entries. The only entry that doesn't need a symmetrical offset is the one that goes through the center of the grid—INTRAVENOUS DRIP here.
This constraint explains further why both Shenk and I chose our five entries: The 10-13-15-13-10 pattern is beautifully symmetrical. An otherwise good nine-letter entry like film director WES CRAVEN (extra points since he's a horror director and this is a creepily themed puzzle) was unfortunately left on the cutting-room floor. I simply couldn't find another nine-letter entry to offset it.
Why, then, were the five entries placed the same?INTRAVENOUS DRIP, as the only 15-letter entry, had to go in the center. Putting the 10-letter entries in the third and 13th rows was also a no-brainer: nine-, 10-, and 11-letter entries fit nicely on the third and 13th rows of a standard 15-by-15 grid, as they allow the top two rows to be broken into chunks of four-, four-, and five-letter words. (More on this later.) A 13-letter entry doesn't fit in row three—it would require awkward clusters of black squares—so it's relegated to the center of the grid.
Why did Shenk and I both place CONTRAVENE on top and COBRA VENOM on the bottom? Imagine a cheese tasting, in which you start off with the mildest cheese and build your way up to the show-stopping sharpest. The principle is the same here: People tend to solve crosswords from the top to the bottom, so we both chose to lead off with the dullish CONTRAVENE (a semi-boring word that semi-boringly embeds the keyword completely inside) and finish with the awesome COBRA VENOM (snakes are very cool creatures, plus the keyword is divided in an unexpected way).
The only real coincidence is that we both chose to put our AVENUES in the fifth row and BRAVE NEW WORLD in the 11th. Those very well might have been reversed, but the 50-50 shot worked out this time.
Why is the black-square pattern so similar? Because a series of crossword rules makes it likely. American crosswords disallow two-letter words, meaning a 15-by-15 grid is likely to be filled with many three-, four-, and five-letter entries. This is especially true of grids with five theme entries, on the highish end for a 15-by-15 grid.
The only reason our black square patterns weren't even more similar is that Shenk needed to fit the word RAVEN into his grid, tipping off his audience as to the embedded keyword. My grid didn't include RAVEN, since it was critical to my weekly crossword contest that week that solvers figure out that RAVEN link without a secondary hint.
As logical as this all sounds after the fact, I couldn't help wondering how close a third constructor would come to replicating these two RAVEN grids. Our contestant: Merl Reagle, often considered the greatest crossword writer in American history and, like Shenk, an idol of mine since childhood. (They're two of the six constructors to whom I dedicated my 2006 book Gridlock: Crossword Puzzles and the Mad Geniuses Who Create Them.)
I asked Reagle, who hadn't seen either of our puzzles, to write a 15-by-15 crossword with RAVEN theme entries. He sent me this grid skeleton the next morning:
Not as similar as mine and Shenk's, but still pretty damn close. Reagle went with six theme entries instead of five, four of which were the same as mine: CONTRAVENE, COBRA VENOM, VENTNOR AVENUEand BRAVE NEW WORLD. He chose to exclude INTRAVENOUS DRIPin favor of WES CRAVEN and, to offset it, the nine-letter NEVERMORE, which he intended to clue as "When I'll make another puzzle like this" (a typically humorous Reagle twist).
When will I make another puzzle like this—that is, conjuring up a theme that's already been done? Probably soon, just as other constructors will copy my crossword concepts. Fortunately, even puzzles with common themes won't be identical—the shorter words (the "fill," in crossword terminology) will certainly be different, as will the clues. Crosswords are like snowflakes, you see—even the ones that look a lot alike are still unique.