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<style class="cp-pen-styles">/**
* Parallax styles
*
* All aesthetic styles are at the bottom for the benefit of better understanding the demo.
*/
html {
/* Give our document a fake height for demo purposes. */
height: 1500px;
/* We must set out root `font-size` to 0 to prevent our parallax margins being calculated */
font-size: 0;
}
body {
/* Reset the `font-size` to 16px/1em/100% */
font-size: 16px;
}
/* Fix our parallax elements in position */
.parallax {
position: fixed;
}
/**
* Position our elements
*
* Firstly we set our element position using `top`, `right`, `bottom`, `left`, then set your parallax movement using `margin` and `rem`.
*
* In this demo our 'base factor' is 50 (see JavaScript). Our 'factor' calculation never exceeds this number (when the viewport is fully scrolled), which means our `rem` calculations are based on this number.
*
* Example:
*
* If I set my `top` to `200px` and want this element to shift up by `400px`, our `rem` value is 400/10, or `-40em` (using negative margins to shift upwards).
*/
h1 {
top: 75px;
margin-top: -3rem;
z-index: 5;
}
.box {
top: -1400px;
/* Positive margin, so it appears from above */
margin-top: 29rem;
/* Center and pad */
left: 50%;
margin-left: -27%;
padding: 2%;
width: 50%;
}
.btn {
top: 5em;
right: -800px;
margin-right: 18.5rem;
}
.skyline {
top: 240px;
margin-top: -28rem;
left: 8%;
}
.blimp {
top: 320px;
margin-top: -55rem;
left: 24%;
}
.gherkin {
top: 200px;
margin-top: -20rem;
left: 40%;
z-index: 10;
}
.bull {
top: 360px;
margin-top: -47rem;
left: 56%;
}
.dino {
top: 260px;
margin-top: -33rem;
left: 72%;
}
/**
* Demo aesthetics
*/
html {
background: #233c38 url('https://goo.gl/5wJBu') 50% 50%;
background-attachment: fixed;
background-size: cover;
font-family: sans-serif;
font-weight: 300;
line-height: 1.5;
color: #fff;
}
a {
color: #fff;
text-decoration: none;
border-bottom: 1px dotted;
}
a:hover {
color: magenta;
}
h1 {
width: 100%;
font: 3em/1 'Oswald', sans-serif;
text-align: center;
text-transform: uppercase;
text-shadow: 3px 3px 20px rgba(0, 0, 0, 0.5);
}
p {
margin: 0 0 1.5em;
}
p:last-child {
margin-bottom: 0;
}
img {
width: 20%;
box-shadow: 0 0 20px rgba(0, 0, 0, 0.4);
}
code {
background-color: #222;
color: magenta;
}
.box {
background-color: rgba(255, 255, 255, 0.1);
}
.btn {
display: inline-block;
padding: 0.5em 1em;
background-color: rgba(0, 0, 0, 0.5);
border-bottom: 0;
}</style></head><body>
<h1 class="parallax">The ‘root element’ parallax technique</h1>
<img src="https://source.unsplash.com/category/nature/600x600" class="parallax skyline">
<img src="https://source.unsplash.com/category/buildings/600x600" class="parallax blimp">
<img src="https://source.unsplash.com/category/food/600x600" class="parallax gherkin">
<img src="https://source.unsplash.com/category/people/600x600" class="parallax dino">
<img src="https://source.unsplash.com/category/technology/600x600" class="parallax bull">
<div class="parallax box">
<p>By combining the power of <code>`rem`</code> and a small JavaScript function to manipulate the <code>`font-size`</code> of the <code>`html`</code> element, we can achieve simple but effective parallaxing.</p>
<p>Setting all our positions and parallax movements in CSS, this technique minimises DOM manipulations to just one – on the <code>`html`</code> element – boosting overall performance, although certainly not better than using 3D transforms.</p>
<p>The speed and direction of each element is set using margins (for this demo I've used <code>`margin-top`</code>). Play around with the numbers yourself to get a better understanding.</p>
<p>This is just a proof of concept and hasn't been fully tested, though it should work everywhere that supports <code>`rem`</code> (<a href="https://caniuse.com/#feat=rem">see here</a>). Using <code>`rem`</code> in this way does have its pitfalls – most notably the loss of its traditional usage – but it's a nice trick.</p>
</div>
<a href="https://codepen.io/amustill/full/aoFIm" target="_blank" class="parallax btn">View full screen</a>
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<script >// Variables
var viewport = $(window),
root = $('html'),
maxScroll;
// Bind events to window
viewport.on({
scroll: function() {
// Grab scroll position
var scrolled = viewport.scrollTop();
/**
* Calculate our factor, setting it as the root `font-size`.
*
* Our factor is calculated by multiplying the ratio of the page scrolled by our base factor. The higher the base factor, the larger the parallax effect.
*/
root.css({ fontSize: (scrolled / maxScroll) * 50 });
},
resize: function() {
// Calculate the maximum scroll position
maxScroll = root.height() - viewport.height();
}
}).trigger('resize');
//# sourceURL=pen.js
</script>
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