Firefox Marketplace Animated Buttons

The Firefox Marketplace is an incredibly attractive, easy to use hub that promises to make finding and promoting awesome HTML5-powered web applications easy and convenient. While I don't work directly on the Marketplace, I am privy to the codebase (and so are you). One of the well written and elegant touches to the site is its animated button. They are comprised completely of CSS and achieve a great effect by animating box-shadow and line-height.

The HTML

These styles can be applied to A elements with the button class or actual BUTTON elements:

<a href="#" class="button" role="button">Arsenal Arsenal Arsenal</a>

Since BUTTON elements have had styling quirks in the past, you'll want to use A elements everywhere outside of forms.

The CSS

There's a lot of CSS in the basic element state, but I kept all of it to keep my demo true to the Marketplace button. Here's the magic:

a.button:link,
a.button:visited,
button,
input[type=submit],
input[type=button] {
	border: 0;
	color: white;
	display: inline-block;
	font: 600 16px/31px "Open Sans","Helvetica Neue",Arial,sans-serif;
	height: 32px;
	background-color: 
	#267CC2;
	padding: 0 24px;
	position: relative;
	text-align: center;
	text-decoration: none;
	text-shadow: 0 1px 0 rgba(0, 0, 0, .25);
	white-space: nowrap;
	border-radius: .5em;
	box-shadow: 0 2px 1px rgba(0, 0, 0, .2), inset 0 -1px 0 rgba(0, 0, 0, .2), inset 0 1px 0 0 rgba(255, 255, 255, .2);
	background-color: #267CC2;
	background-image: linear-gradient(#42A5E1, #267CC2);
	transition-property: -moz-box-shadow,-webkit-box-shadow,box-shadow,line-height;
	transition-duration: .2s,.2s,.2s,.2s;
}

a.button:hover,
a.button:focus,
button:hover,
button:focus,
input[type=submit]:hover,
input[type=button]:hover,
input[type=submit]:focus,
input[type=button]:focus {
    box-shadow: 0 4px 1px rgba(0, 0, 0, 0.2), 0 -3px 0 rgba(0, 0, 0, 0.2) inset;
	line-height: 28px;
	text-decoration: none;
}

a.button:active, button.button:active {
    box-shadow: inset 0 2px 0 0 rgba(0, 0, 0, .2), inset 0 12px 24px 6px rgba(0, 0, 0, .2), inset 0 0 2px 2px rgba(0, 0, 0, .2);
	transition-duration: .1s,.1s,.1s,.1s;
	line-height: 34px;
}

As you can probably guess, the original CSS was generated using a preprocessor (LESS, in this case). As with any piece of expertly written code, there isn't too much to explain. The animated transition is applied to box-shadow and line-height properties and the :active and :hover states trigger the animations.

I love what the AMO and Marketplace team has done with this subtle effect. Not only is the effect smooth and unique, it requires no JavaScript and uses what have now become standard effect techniques. Love it!