This article was originally published by A List Apart and is reproduced
by kind permission.
Back when video games were still fun (we're talking about the 8-bit glory
days here), graphics were a much simpler matter by necessity. Bitmapped 2-dimensional
character data and background scenery was individually drawn, much like today's
resurgent pixel art. Hundreds and later thousands of small graphics called
sprites were the building blocks for all things visual in a game
As game complexity increased, techniques developed to manage the multitude
of sprites while keeping game play flowing. One variation saw sprites being
plugged into a master grid, then later pulled out as needed by code that mapped
positions of each individual graphic, and selectively painted them on the
And what does this have to do with the web?
Everything old is new again, and though the rise of 3D games has made sprite
maps obsolete, the concurrent rise of mobile devices with 2D gaming capabilities
have brought them back into vogue. And now, with a bit of math and a lot of
CSS, we're going to take the basic concept and apply it to the world of web
Specifically, we're going to replace old-school image slicing and dicing
CSS works, we're going to take it further: by building a grid of images and
devising a way to get each individual cell out of the grid, we can store all
buttons/navigation items/whatever we wish in a single master image file, along
with the associated "before" and "after" link states.
How do CSS Sprites work?
As it turns out, the basic tools to do this are built into CSS, given a bit
of creative thinking.
Let's start with the master image itself. Dividing a rectangle into four
items, you'll observe in this master image (below) that our intended "before"
link images are on the top row, with "after" :hover states immediately
There's no clear division between the four links at the moment, so imagine
that each piece of text is a link for now. (For the sake of simplicity, we'll
continue to refer to link images as "before" images and the
state as "after" for the rest of this article. It's possible to
extend this method to
links states as well, but we won't go into that here.)
Those familiar with Petr Stanicek's (Pixy) Fast Rollovers
may already see where we're going with this. This article owes a debt of gratitude
to Pixy's example for the basic function we'll be relying on. But let's not
get ahead of ourselves.
On to the HTML. Every good CSS trick strives to add a layer of visuals on
top of a clean block of code, and this technique is no exception:
<li id="panel1b"><a href="#1"></a></li>
<li id="panel2b"><a href="#2"></a></li>
<li id="panel3b"><a href="#3"></a></li>
<li id="panel4b"><a href="#4"></a></li>
This code will serve as a base for our example. Light-weight, simple markup
that degrades well in older and CSS-disabled browsers is all the rage, and
it's a trend that's good for the industry. It's a great ideal to shoot for.
(We'll ignore any text inside the links for the time being. Apply your favorite
technique later to hide the text you'll end up adding.)