Balancing on a pivot with Flexbox

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Let me show you a way I recently discovered to center a bunch of elements around what I call the pivot. I promise you that funky HTML is out of the question and you won’t need to know any bleeding-edge CSS to get the job done.

I’m big on word games, so I recently re-imagined the main menu of my website as a nod to crossword puzzles, with my name as the vertical word, and the main sections of my website across the horizontals.

Here’s how the design looks with the names of some colors instead:

And here’s a sample of the HTML that drives this puzzle:

<div class="puzzle">
  <div class="word">
    <span class="letter">i</span>
    <span class="letter">n</span>
    <span class="letter">d</span>
    <span class="letter">i</span>
    <span class="letter pivot">g</span>
    <span class="letter">o</span>
  </div>
  <!-- MORE WORDS -->
</div>

In this example, the letter g is the pivot. See how it’s not at the halfway mark? That’s the beauty of this challenge.

We could apply an offset to each word using hard-coded CSS or inline custom properties and walk away. It certainly gets an award for being the most obvious way to solve the problem, but there’s a downside — in addition to the .pivot class, we’d have to specify an offset for every word. The voice in my head tells me that’s adding unnecessary redundancy, is less flexible, and requires extra baggage we don’t need every time we add or change a word.

Let’s take a step back instead and see how the puzzle looks without any balancing:

Imagine for a moment that we use display: none to hide all of the letters before the pivot; now all we can see are the pivots and everything after them:

With no further changes, our pivots would already be aligned. But we’ve lost the start of our words, and when we reintroduce the hidden parts, each word gets pushed out to the right and everything is out of whack again.

If we were to hide the trailing letters instead, we’d still be left with misaligned pivots:

All of this back-and-forth seems a bit pointless, but it reveals a symmetry to my problem. If we were to use a right-to-left (RTL) reading scheme, we’d have the opposite problem — we’d be able to solve the right side but the left would be all wrong.

Wouldn’t it be great if there was a way to have both sides line up at the same time?

As a matter of fact, there is.

Given we already have half a solution, let’s borrow a concept from algorithmics called divide and conquer. The general idea is that we can break a problem down into parts, and that by finding a solution for the parts, we’ll find a solution for the whole.

In that case, let’s break our problem down into the positioning of two parts. First is the “head” or everything before the pivot.

Next is the “tail” which is the pivot plus everything after it.

The flex display type will help us here; if you’re not familiar with it, flex is a framework for positioning elements in one-dimension. The trick here is to take advantage of the left and right ends of our container to enforce alignment. To make it work, we’ll swap the head and tail parts by using a smaller order  property value on the tail than the head. The order property is used by flex to determine the sequence of elements in a flexible layout. Smaller numbers are placed earlier in the flow.

To distinguish the head and tail elements without any extra HTML, we can apply styles to the head part to all of the letters, after which we’ll make use of the cascading nature of CSS to override the pivot and everything after it using the subsequent-sibling selector .pivot ~ .letter.

Here’s how things look now:

Okay, so now the head is sitting flush up against the end of the tail. Hang on, don’t go kicking up a stink about it! We can fix this by applying margin: auto to the right of the last element in the tail. That just so happens to also be the last letter in the word which is not sitting somewhere in the middle. The addition of an auto margin serves to push the head away from the tail and all the way over to the right-hand side of our container.

Now we have something that looks like this:

The only thing left is stitch our pieces back together in the right order. This is easy enough to do if we apply position: relative to all of our letters and then chuck a left: 50% on the tail and a right: 50% on our head items.

Here’s a generalized version of the code we just used. As you can see, it’s just 15 lines of simple CSS:

.container {
  display: flex;
}
.item:last-child {
  margin-right: auto;
}
.item {
  order: 2;
  position: relative;
  right: 50%;
}
.pivot, .pivot ~ .item {
  order: 1;
  left: 50%;
}

It’s also feasible to use this approach for vertical layouts by setting the flex-direction to a column value. It should also be said that the same can be achieved by sticking the head and tail elements in their own wrappers — but that would require more markup and verbose CSS while being a lot less flexible. What if, for example, our back-end is already generating an unwrapped list of elements with dynamically generated classes?

Quite serendipitously, this solution also plays well with screen readers. Although we’re ordering the two sections backwards, we’re then shifting them back into place via relative positioning, so the final ordering of elements matches our markup, albeit nicely centered.

Here’s the final example on CodePen:

Conclusion

Developers are better at balancing than acrobats. Don’t believe me? Think about it: many of the common challenges we face require finding a sweet spot between competing requirements ranging from performance and readability, to style and function, and even scalability and simplicity. A balancing act, no doubt.

But the point at which we find balance isn’t always midway between one thing and another. Balance is often found at some inexplicable point in between; or, as we’ve just seen, around an arbitrary HTML element.

So there you have it! Go and tell your friends that you’re the greatest acrobat around.

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