Pen Settings

CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

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.

+ add another resource

You're using npm packages, so we've auto-selected Babel for you here, which we require to process imports and make it all work. If you need to use a different JavaScript preprocessor, remove the packages in the npm tab.

Add External Scripts/Pens

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.

+ add another resource

Use npm Packages

We can make npm packages available for you to use in your JavaScript. We use webpack to prepare them and make them available to import. We'll also process your JavaScript with Babel.

⚠️ This feature can only be used by logged in users.

Code Indentation


Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

HTML Settings

Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

/ Edit the variables below to configure your gif.

const CANVAS_WIDTH = 300 // The width of the canvas
const CANVAS_HEIGHT = 300; // The height of the canvas
const FRAME_COUNT = 30; // The number of frames
const FPS = 15; // Frames per second.
const LOOPS = 0; // 0 = loop forever.
// Whether to clear the canvas after drawing each frame.
const CLEAR_EACH_FRAME = true;

//The DRAW_FRAME function is where you define what a frame should look like. It receives a 2D rendering context as its first argument, and a frame counter as its second. The frame counter starts at 0 for the first frame, and increases by 1 every time the function is called for drawing subsequent frames, up to FRAME_COUNT - 1.
const DRAW_FRAME = (ctx, frame) => {
  // Your implementation goes here.
  // Here's an example that renders a circle that
  // grows and shrinks.
  let scale = Math.abs(frame - FRAME_COUNT/2) / (FRAME_COUNT/2);
  let radius = scale * Math.min(CANVAS_WIDTH, CANVAS_HEIGHT) / 2;
  let circleX = CANVAS_WIDTH / 2;
  let circleY = CANVAS_HEIGHT / 2;
  ctx.fillStyle = "red";
  ctx.arc(circleX, circleY, radius, 0, 2 * Math.PI, false);

// although feel free, if you want to :).

// Set up the canvas.
let can = document.createElement("canvas");
let ctx = can.getContext("2d");
can.width = CANVAS_WIDTH;
can.height = CANVAS_HEIGHT;

// Configure an encoder.
let encoder = new GIFEncoder();
encoder.setDelay(1000 / FPS);

// This is where the magic happens. ✨
for (let i=0; i < FRAME_COUNT; i++){
  console.log("frame " + i);
  DRAW_FRAME(ctx, i);
    ctx.clearRect(0, 0, CANVAS_WIDTH, CANVAS_HEIGHT);

let binary_gif =
let data_url = 'data:image/gif;base64,'+encode64(binary_gif);

let image = document.createElement("img");
image.src = data_url;


let download = document.createElement("button");
download.innerText = "download GIF"; = "display:block;background-color:green;color:white;font-size:2em;";

download.addEventListener("click", () => {"animation.gif");


🕑 One or more of the npm packages you are using needs to be built. You're the first person to ever need it! We're building it right now and your preview will start updating again when it's ready.