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. You can use the CSS from another Pen by using it's URL and the proper URL extention.
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.
You can also link to another Pen here (use the .css
URL Extension) and we'll pull the CSS from that Pen and include it. If it's using a matching preprocessor, use the appropriate URL Extension and 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.
<canvas style="position: relative; cursor: none;" id= "canvas_manual_drawing_demo" width="750" height="800">
</canvas>
// Snake-settings:
var settings = {
segmentLength: 1,
gravity: {x: 0, y: 0},
paintDots: true,
dotCount: 100
}
// Replace above settings with below for a snake-like expression
// var settings = {
// segmentLength: 1,
// gravity: {x: 0, y: 0},
// paintDots: true,
// dotCount: 100
// }
var HEIGHT = 750;
var WIDTH = 800;
var ensureValidNumber = function(n, obj){
if(n === undefined)
{
console.error(obj);
throw "Undefined";
}
if(isNaN(n))
{
console.error(obj);
throw "Nan";
}
if(!isFinite(n)){
console.error(obj);
throw "Infinity";
}
}
var ensureVector = function(v){
var throwAlert = function(msg, obj){
console.error(msg, v);
throw msg;
}
if(!v)
{
throwAlert("Falsy vector!", v);
}
ensureValidNumber(v.x, v);
ensureValidNumber(v.y, v);
}
var createDot = function(x, y){
ensureValidNumber(x);
ensureValidNumber(y);
var result = {loc: {x:x, y:y}, vel: {x: 0, y:0}};
ensureVector(result.loc);
ensureVector(result.vel);
return result;
}
var mainDot = createDot(WIDTH/2, HEIGHT/2-settings.segmentLength);
var dots = [];
var resizeDotCount = function(dotCount){
dots = [];
// Grow if more
for(var i = 0; i < dotCount; i++){
dots.push(createDot(WIDTH/2, HEIGHT/2+i*settings.segmentLength));
ensureVector(dots[i].loc);
ensureVector(dots[i].vel);
}
}
resizeDotCount(settings.dotCount);
var addVector = function(existing, add){
return {x:existing.x + add.x, y: existing.y + add.y};
}
var getDistance = function(loc1, loc2){
ensureVector(loc1);
ensureVector(loc2);
var xDist = loc1.x-loc2.x;
ensureValidNumber(xDist);
var yDist = loc1.y-loc2.y;
ensureValidNumber(yDist);
var v = xDist*xDist + yDist * yDist;
ensureValidNumber(v, {debud1: loc1, debug2: loc2});
var result = Math.sqrt(v);
ensureValidNumber(result, v);
return result;
}
var getVectorLength = function(vector){
ensureVector(vector);
var existinglength = getDistance({x:0,y:0}, vector);
ensureValidNumber(existinglength);
return existinglength;
}
var setVectorLength = function(vector, length){
if(length == 0)
return {x:0, y:0};
ensureValidNumber(length, length);
ensureVector(vector);
var existinglength = getVectorLength(vector);
ensureValidNumber(existinglength);
if(existinglength == 0)
return {x:0, y:0};
var newX = vector.x / existinglength * length;
ensureValidNumber(newX);
var newY = vector.y / existinglength * length;
ensureValidNumber(newY);
var newVector = {x: newX, y: newY};
ensureVector(newVector);
return newVector;
}
var getDistanceVector = function(loc1, loc2){
var distance = {x: loc2.x - loc1.x, y:loc2.y - loc1.y};
ensureVector(distance);
return distance;
}
var adjustVectorLength = function(vector, factor){
ensureVector(vector);
ensureValidNumber(factor);
var length = getVectorLength(vector);
ensureValidNumber(length);
var newLength = length * factor;
ensureValidNumber(newLength);
var newVector = setVectorLength(vector, newLength);
ensureVector(newVector);
return newVector;
}
// Logic
var updateLogic = function(){
var previousDot = mainDot;
for(var i = 0; i < dots.length; i++){
var dot = dots[i];
// Validation
ensureVector(previousDot.loc);
ensureVector(dot.loc);
// Apply dot's own velocity to dot
dot.loc = addVector(dot.loc, dot.vel);
// Get vector from this position to previous nodes position
var directionVector = {x: dot.loc.x - previousDot.loc.x, y: dot.loc.y - previousDot.loc.y};
var directionVector = setVectorLength(directionVector, settings.segmentLength);
// Calculate the position where the dot should be moved to
var desiredNewPosition = {x:previousDot.loc.x + directionVector.x, y: previousDot.loc.y + directionVector.y};
// Calculate the velocity to apply to the dot based on the instant movement to a new position
var positionMoveVelocity = {x: desiredNewPosition.x - dot.loc.x, y: desiredNewPosition.y - dot.loc.y};
// Slow down the position move velocity to make the tail relax faster
positionMoveVelocity = adjustVectorLength(positionMoveVelocity, 0.5); // The closer to one, the longer time willt he tail vibrate
// Apply position move velocity
dot.vel = addVector(dot.vel, positionMoveVelocity);
// Add settings.gravity
dot.vel = addVector(dot.vel, settings.gravity);
// Brake velocity for a slow movement
dot.vel = adjustVectorLength(dot.vel, 0.8); // The closer to 1, the faster does the tail move
// The difference from current position to desired position is added to the velocity as a force
dot.loc = desiredNewPosition;
// Move to next dot in line
previousDot = dot;
}
}
// Drawing
var canvas = document.getElementById("canvas_manual_drawing_demo");
var ctx = canvas.getContext("2d");
// Controls
var active = false;
canvas.addEventListener("mouseenter", function (e) {
active = true;
});
canvas.addEventListener("mouseleave", function (e) {
active = false;
});
canvas.addEventListener("mousemove", function (e) {
mainDot.loc.x = e.layerX;
mainDot.loc.y = e.layerY;
});
var repaint = function(){
// Clear
ctx.fillStyle = "#999";
ctx.fillRect(0, 0, canvas.width, canvas.height);
// Draw line
ctx.strokeStyle = "rgb(144,80,80)";
ctx.beginPath();
ctx.moveTo(mainDot.loc.x, mainDot.loc.y);
// Draw line
for(var i = 0; i < dots.length; i++){
var dot = dots[i];
ctx.lineTo(dot.loc.x, dot.loc.y);
ctx.stroke();
}
// Draw dots
if(settings.paintDots){
ctx.fillStyle = "#F00";
var dotWidth = 4;
for(var i = 0; i < dots.length; i++){
var dot = dots[i];
ctx.fillRect(dot.loc.x-dotWidth/2, dot.loc.y-dotWidth/2, dotWidth, dotWidth);
}
}
}
var paintPauseText = function(){
ctx.strokeStyle = "#000";
ctx.font = "20px Arial";
ctx.fillText("(Paused to save resources - hover to activate)", 150, 50);
}
repaint();
var pausePainted = false; // This is used to only draw text once whan paused to save resources
var tick = function(){
if(active){
updateLogic();
repaint();
pausePainted = false;
}else{
if(!pausePainted){
paintPauseText();
pausePainted = true;
}
}
setTimeout(tick, 25);
}
tick();
Also see: Tab Triggers