Building a crooked grid illusion

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• Overview
• Markup
• Styles
• Body styles
• Row styles
• Square styles
• Conclusion
• Community remixes

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In this post we're going to have a little bit of fun! There must be 100 ways to achieve this optical illusion, and I'm only going to share with you my thoughts, but encourage you to try your style. Try the demo and view the source.

If you prefer video, here's a YouTube version of this post:

https://www.youtube.com/watch?v=71jpjr7syc4

Overview

The name of this illusion is the Cafe Wall Illusion. There's no crooked lines to be found anywhere, but our eyes perceive slants. It may be hard to believe, but rebuilding it will definitely help you see through the illusion.

To help you kick off this challenge, here's a Codepen you can fork which has all the HTML ready for you to style your way.

Markup

The HTML for this is straightforward rows and columns. The <body> is the container with <div class="row"> for children. Each row contains five <div class="square"> elements.

<div class="row">
  <div class="square"></div>
  <div class="square"></div>
  <div class="square"></div>
  <div class="square"></div>
  <div class="square"></div>
</div>
…

Styles

I chose CSS grid because it seemed fitting given the presentation style of rows, and it also features justify-content which seemed like a good way to offset row children.

Body styles

Starting with the body styles, I used display: grid and grid-auto-rows to provide the row layouts. The calc() you see for the row sizes takes into account the border on each row, and helps the effect fit the full viewport.

body {
  display: grid;
  grid-auto-rows: calc(20vh - 4px);
  gap: 4px;
  background: gray;
  margin: 0;
}

Row styles

Here I chose grid again, but instead of creating rows with it I used grid-auto-flow: column to change the direction to columns. I then define column sizes and add a little inline padding to the row, so boxes don't run into the viewport edge. Then I target certain rows and justify the content to either center or end, creating that offset that fuels the illusion.

.row {
  display: grid;
  grid-auto-flow: column;
  grid-auto-columns: 9vw;
  padding-inline: 4vw;
  gap: 10vw;
  background: white;
}

.row:nth-child(even) {
  justify-content: center;
}

.row:nth-child(3n) {
  justify-content: end;
}

Square styles

All that's left now is to change the squares color and add a border:

.square {
  border-inline: 4px solid gray;
  background: black;
}

Conclusion

Now that you know how I did it, how would you?! 🙂 Floats? Flexbox? Gradient?!

Let's diversify our approaches and learn all the ways to build on the web.

Create a demo, tweet me links, and I'll add it to the community remixes section below!

Community remixes

• Mark Boots with gradients: demo and code