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.
In CodePen, whatever you write in the HTML editor is what goes within the <body>
tags in a basic HTML5 template. So you don't have access to higher-up elements like the <html>
tag. If you want to add classes there that can affect the whole document, this is the place to do it.
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.
The resource you are linking to is using the 'http' protocol, which may not work when the browser is using https.
CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.
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.
To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit-
or -moz-
.
We offer two popular choices: Autoprefixer (which processes your CSS server-side) and -prefix-free (which applies prefixes via a script, client-side).
Any URL's added here will be added as <link>
s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.
You can apply CSS to your Pen from any stylesheet on the web. Just put a URL to it here and we'll apply it, in the order you have them, before the CSS in the Pen itself.
If the stylesheet you link to has the file extension of a preprocessor, we'll attempt to process it before applying.
You can also link to another Pen here, and we'll pull the CSS from that Pen and include it. If it's using a matching preprocessor, we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency.
JavaScript preprocessors can help make authoring JavaScript easier and more convenient.
Babel includes JSX processing.
Any URL's added here will be added as <script>
s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.
You can apply a script from anywhere on the web to your Pen. Just put a URL to it here and we'll add it, in the order you have them, before the JavaScript in the Pen itself.
If the script you link to has the file extension of a preprocessor, we'll attempt to process it before applying.
You can also link to another Pen here, and we'll pull the JavaScript from that Pen and include it. If it's using a matching preprocessor, we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency.
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.
Using packages here is powered by Skypack, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ES6 import
usage.
All packages are different, so refer to their docs for how they work.
If you're using React / ReactDOM, make sure to turn on Babel for the JSX processing.
If active, Pens will autosave every 30 seconds after being saved once.
If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.
If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.
Visit your global Editor Settings.
body {
background: #333;
margin: 0;
overflow: hidden;
}
canvas {
background: black;
}
var App = {};
jQuery(document).ready(function() {
// Setup canvas and app
App.setup();
// Launch animation loop
App.frame = function() {
App.update();
window.requestAnimationFrame(App.frame);
};
App.frame();
jQuery('canvas#ourCanvas').on('click', function(event) {
App.hasUserClicked = !App.hasUserClicked;
});
jQuery('canvas#ourCanvas').on('mousemove', function(event) {
App.target.x = event.pageX;
App.target.y = event.pageY;
});
});
App.setup = function() {
// Setup canvas and get canvas context
var canvas = document.createElement('canvas');
canvas.height = window.innerHeight;
canvas.width = window.innerWidth;
canvas.id = 'ourCanvas';
document.body.appendChild(canvas);
this.ctx = canvas.getContext('2d');
this.width = canvas.width;
this.height = canvas.height;
// Define a few useful elements
this.stepCount = 0;
this.hasUserClicked = false;
this.xC = canvas.width / 2;
this.yC = canvas.height / 2;
this.target = {
x: this.xC,
y: this.yC,
radius: 20
};
this.armsPop = 20;
//this.particlesPerArm = 15;
// Create initial targets and arms
this.arms = [];
for (var i = 0; i < this.armsPop; i++) {
this.arms.push([]);
}
// Fill initial arms
this.initialBirth();
// Some forces
this.gravity = -1;
this.springStiffness = 0.5;
this.viscosity = 0.1;
this.isElastic = false;
};
App.initialBirth = function() {
for (var armIndex = 0; armIndex < this.arms.length; armIndex++) {
var arm = this.arms[armIndex];
// Random arm length! Sorta.
var particlesNb = 20 + Math.ceil(20 * Math.random());
for (var i = 0; i < particlesNb; i++) {
var x = this.width * Math.random();
var y = this.height * Math.random();
var particle = {
x: x,
y: y,
xLast: x,
yLast: y,
xSpeed: 0,
ySpeed: 0,
stickLength: 10,
name: 'seed' + this.stepCount
};
arm.push(particle);
}
}
};
App.update = function() {
// Evolve system
this.evolve();
// Move particles
this.move();
// Draw particles
this.draw();
};
App.evolve = function() {
this.stepCount++;
this.target.radius = 50 + 30 * Math.sin(this.stepCount / 10);
};
App.move = function() {
// This is inverse kinematics, the particles form an arm with N joints, and its shape adapts with a target contraint
// Move target point
if (!this.hasUserClicked) {
this.target.x = this.xC + 150 * Math.cos(this.stepCount / 50);
this.target.y = this.yC + 150 * Math.sin(this.stepCount / 20);
}
// Move particles accordingly (on each arm)
for (var armIndex = 0; armIndex < this.arms.length; armIndex++) {
var arm = this.arms[armIndex];
var ownTargetAngle = 2 * Math.PI * armIndex / this.arms.length;
var ownTarget = {
x: this.target.x + this.target.radius * Math.cos(ownTargetAngle),
y: this.target.y + this.target.radius * Math.sin(ownTargetAngle),
}
for (var i = 0; i < arm.length; i++) {
var p = arm[i];
// Leading particle (particle bound to head at first, then the preceding particle)
var pLead = ( i == 0 ? ownTarget : arm[i-1] );
var angle = segmentAngleRad(p.x, p.y, pLead.x, pLead.y, false);
var dist = Math.sqrt(Math.pow(p.x - pLead.x, 2) + Math.pow(p.y - pLead.y, 2));
var translationDist = dist - p.stickLength;
if (translationDist < 0) {
angle += Math.PI;
translationDist = Math.abs(translationDist);
}
/* Kinetic binding */
// Rotation, then translation for each particle/stick from head to tail
var dx = translationDist * Math.cos(angle);
var dy = translationDist * Math.sin(angle);
if (!this.isElastic) {
p.x += dx;
p.y -= dy;
}
/* Forces */
var xAcc = this.springStiffness * dx - this.viscosity * p.xSpeed;
var yAcc = this.springStiffness * dy + this.gravity - this.viscosity * p.ySpeed;
p.xSpeed += xAcc;
p.ySpeed += yAcc;
p.x += 0.1 * p.xSpeed;
p.y -= 0.1 * p.ySpeed;
}
}
};
App.draw = function() {
// Add transparent layer for trace effect
this.ctx.beginPath();
this.ctx.rect(0, 0, this.width, this.height);
this.ctx.fillStyle = 'rgba(0, 0, 0, 0.3)';
this.ctx.fill();
// Draw target
this.ctx.beginPath();
this.ctx.arc(this.target.x, this.target.y, 15, 0, 2 * Math.PI, false);
this.ctx.fillStyle = 'rgba(255, 255, 255, 0.1)';
this.ctx.fill();
// Draw particles
for (var armIndex = 0; armIndex < this.arms.length; armIndex++) {
var arm = this.arms[armIndex];
for (var i = 0; i < arm.length; i++) {
var particle = arm[i];
if (i != 0) { var particleLead = arm[i-1]; }
// Draw particle
this.ctx.beginPath();
this.ctx.arc(particle.x, particle.y, 0.3 * (arm.length - i), 0, 2 * Math.PI, false);
this.ctx.strokeStyle = 'hsla(' + (200 + i * 4) + ', 90%, 50%, 0.7)';
this.ctx.stroke();
// Draw its stick
this.ctx.beginPath();
this.ctx.lineWidth = 1;
this.ctx.strokeStyle = 'hsla(' + (180 + i * 4) + ', 80%, 50%, 0.7)';
if (i == 0) this.ctx.moveTo(this.target.x, this.target.y);
else this.ctx.moveTo(particleLead.x, particleLead.y);
this.ctx.lineTo(particle.x, particle.y);
this.ctx.stroke();
}
}
};
/**
* @param {Number} Xstart X value of the segment starting point
* @param {Number} Ystart Y value of the segment starting point
* @param {Number} Xtarget X value of the segment target point
* @param {Number} Ytarget Y value of the segment target point
* @param {Boolean} realOrWeb true if Real (Y towards top), false if Web (Y towards bottom)
* @returns {Number} Angle between 0 and 2PI
*/
segmentAngleRad = function(Xstart, Ystart, Xtarget, Ytarget, realOrWeb) {
var result;// Will range between 0 and 2PI
if (Xstart == Xtarget) {
if (Ystart == Ytarget) {
result = 0;
} else if (Ystart < Ytarget) {
result = Math.PI/2;
} else if (Ystart > Ytarget) {
result = 3*Math.PI/2;
} else {}
} else if (Xstart < Xtarget) {
result = Math.atan((Ytarget - Ystart)/(Xtarget - Xstart));
} else if (Xstart > Xtarget) {
result = Math.PI + Math.atan((Ytarget - Ystart)/(Xtarget - Xstart));
}
result = (result + 2*Math.PI)%(2*Math.PI);
if (!realOrWeb) {
result = 2*Math.PI - result;
}
return result;
}
Also see: Tab Triggers