Like nearly all crosswords, cryptic or standard, our puzzles generally have grids that are symmetrical. This is a long-standing practice in the world of English-language crosswords, and it has a number of reasons—many of them good.

Symmetry fosters a general sense of aesthetic balance, and more specifically, it helps distribute the quality of entries evenly. As we mentioned in a long-ago blog post, in French grids—which don’t have an expectation of symmetry—constructors too often place their best work in the northwest corner of the grid, where solvers begin their work, and leave the dregs for the lower right.

But like all rules and conventions, the symmetry principle is one that can, and should, be broken now and again. Attempting to work within the guidelines of symmetry is a helpful discipline for constructors. Yet when symmetry makes it absolutely impossible to achieve a specific goal in constructing a puzzle—a particular theme, say, or a confluence of vivid entries—there’s no reason why it shouldn’t simply be jettisoned.

In the world of non-cryptic puzzles, this freewheeling attitude has long been espoused by Peter Gordon, the visionary editor and constructor who oversees Fireball Crosswords (and was the editor of the invaluable New York Sun crossword, now sadly defunct). Constructor Frank Longo, in his published collections of “Absolutely Nasty” crosswords, often fills his grids with long, densely packed entries, and forgoes symmetry for the purpose.

Instead of rejecting symmetry altogether, there are alternative forms that can be adopted when traditional 180-degree symmetry fails. It’s not all that uncommon, for instance, for a crossword grid to be symmetrical across a vertical axis (Wednesday’s New York Times crossword was an apt example). And in this week’s American Values Club crossword, constructor Francis Heaney found himself with a set of theme entries that weren’t symmetrical—and neatly solved the problem by placing them in a grid with diagonal symmetry.

In addition, a theme whose component entries aren’t of comparable length can still be fitted asymmetrically into a symmetrical grid—a different level of balance that we discussed here and put into practice in Puzzle #3269 and Puzzle #3304, among others.

The grid for this week’s Nation cryptic is not symmetrical, but this did not seem to be noticed by our test solvers. We did this because we wanted to include the three long entries, even though they weren’t of balanced lengths. We did the same thing once before, in Puzzle #3331, and for the a similar reason—because there more thematic entries than we could fit into a symmetrical grid of the requisite size.

Those are two of the three times we’ve used an asymmetrical grid. The third instance was pretty recently, in Puzzle #3348. That time we did it because ASYMMETRY was one of the puzzle answers—and how better to define the word than with a grid that exemplifies it?

This week’s cluing challenge: MIRROR. To comment (and see other readers’ comments), please click on this post’s title and scroll to the bottom of the resulting screen. And now, four links: • The current puzzle • Our puzzle-solving guidelines | PDF • Our e-books (solve past puzzles on your iOS device—many hints provided by the software!) • A Nation puzzle solver’s blog where every one of our clues is explained in detail. This is also where you can post quibbles, questions, kudos or complaints about the current puzzle, as well as ask for hints.