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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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Adding Classes

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About the <head>

In CodePen, whatever you write in the HTML editor is what goes within the <body> tags in a basic HTML5 template. If you need things in the <head> of the document, put that code here.

!
Insecure Resource

The resource you are linking to is using the 'http' protocol, which may not work when the browser is using https.

CSS

About CSS Preprocessors

CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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Packages

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Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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HTML 

              
                <p>
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer feugiat quis nisi vel viverra. Maecenas tincidunt egestas tristique. Phasellus rhoncus tortor in elit vehicula, eu venenatis erat vestibulum. In ut neque et ante ornare venenatis. Morbi quis enim a metus gravida imperdiet. In hac habitasse platea dictumst. In maximus id nulla in ullamcorper. Suspendisse auctor rhoncus mi non laoreet. Aliquam erat volutpat.
<br /><br />
Vestibulum at rutrum ligula. Vivamus vel pulvinar ipsum. Aliquam quis ipsum turpis. Nulla lobortis tortor id ornare finibus. Etiam porta, sem eu condimentum viverra, eros quam aliquet ex, ut suscipit orci quam a diam. Nullam neque lacus, venenatis quis gravida a, fringilla ut metus. Quisque id ante velit. Curabitur suscipit ipsum nec ante venenatis, et mattis lacus porttitor. Proin pharetra dui vel lectus ultrices, vel pharetra turpis facilisis. Class aptent taciti sociosqu ad litora torquent per conubia nostra, per inceptos himenaeos.
</p>
!

CSS 

              
                html{
  background-color:#333;
  color:#fff;
  overflow-x:hidden;
}
!

JS 

              
                // <![CDATA[
if ((document.getElementById) &&
    window.addEventListener || window.attachEvent) {

    (function() {

        //Configure here.

        var num = 30; //Number of flakes
        var timer = 30; //setTimeout speed. Varies on different comps
        var enableinNS6 = 1 //Enable script in NS6/Mozilla? Snow animation could be slow in those browsers. (1=yes, 0=no).

        //End.

        var y = [];
        var x = [];
        var fall = [];
        var theFlakes = [];
        var sfs = [];
        var step = [];
        var currStep = [];
        var h, w, r;
        var d = document;
        var pix = "px";
        var domWw = (typeof window.innerWidth == "number");
        var domSy = (typeof window.pageYOffset == "number");
        var idx = d.getElementsByTagName('div').length;

        if (d.documentElement.style &&
            typeof d.documentElement.style.MozOpacity == "string")
            num = 12;

        for (i = 0; i < num; i++) {
            sfs[i] = Math.round(1 + Math.random() * 1);

            document.write('<div id="flake' + (idx + i) + '" style="position:absolute;top:0px;left:0px;width:' + sfs[i] + 'px;height:' + sfs[i] + 'px;background-color:#ffffff;font-size:' + sfs[i] + 'px"><\/div>');

            currStep[i] = 0;
            fall[i] = (sfs[i] == 1) ?
                Math.round(2 + Math.random() * 2) : Math.round(3 + Math.random() * 2);
            step[i] = (sfs[i] == 1) ?
                0.05 + Math.random() * 0.1 : 0.05 + Math.random() * 0.05;
        }


        if (domWw) r = window;
        else {
            if (d.documentElement &&
                typeof d.documentElement.clientWidth == "number" &&
                d.documentElement.clientWidth != 0)
                r = d.documentElement;
            else {
                if (d.body &&
                    typeof d.body.clientWidth == "number")
                    r = d.body;
            }
        }

        function winsize() {
            var oh, sy, ow, sx, rh, rw;
            if (domWw) {
                if (d.documentElement && d.defaultView &&
                    typeof d.defaultView.scrollMaxY == "number") {
                    oh = d.documentElement.offsetHeight;
                    sy = d.defaultView.scrollMaxY;
                    ow = d.documentElement.offsetWidth;
                    sx = d.defaultView.scrollMaxX;
                    rh = oh - sy;
                    rw = ow - sx;
                } else {
                    rh = r.innerHeight;
                    rw = r.innerWidth;
                }
                h = rh - 2;
                w = rw - 2;
            } else {
                h = r.clientHeight - 2;
                w = r.clientWidth - 2;
            }
        }

        function scrl(yx) {
            var y, x;
            if (domSy) {
                y = r.pageYOffset;
                x = r.pageXOffset;
            } else {
                y = r.scrollTop;
                x = r.scrollLeft;
            }
            return (yx == 0) ? y : x;
        }

        function snow() {
            var dy, dx;

            for (i = 0; i < num; i++) {
                dy = fall[i];
                dx = fall[i] * Math.cos(currStep[i]);

                y[i] += dy;
                x[i] += dx;

                if (x[i] >= w || y[i] >= h) {
                    y[i] = -10;
                    x[i] = Math.round(Math.random() * w);
                    fall[i] = (sfs[i] == 1) ?
                        Math.round(2 + Math.random() * 2) : Math.round(3 + Math.random() * 2);
                    step[i] = (sfs[i] == 1) ?
                        0.05 + Math.random() * 0.1 : 0.05 + Math.random() * 0.05;
                }

                theFlakes[i].top = y[i] + scrl(0) + pix;
                theFlakes[i].left = x[i] + scrl(1) + pix;

                currStep[i] += step[i];
            }
            setTimeout(snow, timer);
        }

        function init() {
            winsize();
            for (i = 0; i < num; i++) {
                theFlakes[i] = document.getElementById("flake" + (idx + i)).style;
                y[i] = Math.round(Math.random() * h);
                x[i] = Math.round(Math.random() * w);
            }
            snow();
        }

        if (window.addEventListener) {
            window.addEventListener("resize", winsize, false);
            window.addEventListener("load", init, false);
        } else if (window.attachEvent) {
            window.attachEvent("onresize", winsize);
            window.attachEvent("onload", init);
        }

    })();
}
// ]]>
!
999px

Console