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HTML

About HTML Preprocessors

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

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.

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

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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

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).

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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.

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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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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.

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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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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.

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HTML 

              
                <div class='container'>
    <div class='canvas-wrapper'>
        <canvas id='canvas'></canvas>
    </div>
</div>


<script id='vertex-shader' type='x-shader/x-vertex'>
    precision mediump float;

    attribute vec2 a_position;

    void main() {
        gl_Position = vec4(a_position, 0, 1);
    }
</script>


<script id='fragment-shader' type='x-shader/x-fragment'>
    precision mediump float;

    uniform sampler2D u_texture;
    uniform float u_canvas_size;
    uniform float u_time;
    uniform vec2 u_mouse_position;

    void main() {
        vec2 texture_coord = gl_FragCoord.xy / u_canvas_size;
        float block_size = abs(sin(u_time)) / 20.0;
        vec2 block_position = floor(texture_coord / block_size) * block_size;

        gl_FragColor = (
                texture2D(u_texture, block_position)
                + texture2D(u_texture, block_position + vec2(1.0, 0.0) * block_size) 
                + texture2D(u_texture, block_position + vec2(0.0, 1.0) * block_size) 
                + texture2D(u_texture, block_position + vec2(1.0, 1.0) * block_size) 
            ) / 4.0;
    }
</script>
!

CSS 

              
                * {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}


.container {
    position: absolute;
    height: 90vmin;
    width: 90vmin;
    top: 50%;
    left: 50%;
    transform: translateX(-50%) translateY(-50%);
    box-shadow: 0 0 1rem rgba(0, 0, 0, .3);
    overflow: hidden;
    border-radius: 5px;
    padding: 15px;
    background: rgba(255, 255, 255, .9);
}

.canvas-wrapper {
    border-radius: 5px;
    overflow: hidden;
}

canvas {
    display: block;
}

body {
    overflow: hidden;


background-color: #00140a;
background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='100%25'%3E%3Cdefs%3E%3ClinearGradient id='a' gradientUnits='userSpaceOnUse' x1='0' x2='0' y1='0' y2='100%25' gradientTransform='rotate(338,683,336)'%3E%3Cstop offset='0' stop-color='%2300140a'/%3E%3Cstop offset='1' stop-color='%23261212'/%3E%3C/linearGradient%3E%3Cpattern patternUnits='userSpaceOnUse' id='b' width='300' height='250' x='0' y='0' viewBox='0 0 1080 900'%3E%3Cg fill-opacity='0.02'%3E%3Cpolygon fill='%23444' points='90 150 0 300 180 300'/%3E%3Cpolygon points='90 150 180 0 0 0'/%3E%3Cpolygon fill='%23AAA' points='270 150 360 0 180 0'/%3E%3Cpolygon fill='%23DDD' points='450 150 360 300 540 300'/%3E%3Cpolygon fill='%23999' points='450 150 540 0 360 0'/%3E%3Cpolygon points='630 150 540 300 720 300'/%3E%3Cpolygon fill='%23DDD' points='630 150 720 0 540 0'/%3E%3Cpolygon fill='%23444' points='810 150 720 300 900 300'/%3E%3Cpolygon fill='%23FFF' points='810 150 900 0 720 0'/%3E%3Cpolygon fill='%23DDD' points='990 150 900 300 1080 300'/%3E%3Cpolygon fill='%23444' points='990 150 1080 0 900 0'/%3E%3Cpolygon fill='%23DDD' points='90 450 0 600 180 600'/%3E%3Cpolygon points='90 450 180 300 0 300'/%3E%3Cpolygon fill='%23666' points='270 450 180 600 360 600'/%3E%3Cpolygon fill='%23AAA' points='270 450 360 300 180 300'/%3E%3Cpolygon fill='%23DDD' points='450 450 360 600 540 600'/%3E%3Cpolygon fill='%23999' points='450 450 540 300 360 300'/%3E%3Cpolygon fill='%23999' points='630 450 540 600 720 600'/%3E%3Cpolygon fill='%23FFF' points='630 450 720 300 540 300'/%3E%3Cpolygon points='810 450 720 600 900 600'/%3E%3Cpolygon fill='%23DDD' points='810 450 900 300 720 300'/%3E%3Cpolygon fill='%23AAA' points='990 450 900 600 1080 600'/%3E%3Cpolygon fill='%23444' points='990 450 1080 300 900 300'/%3E%3Cpolygon fill='%23222' points='90 750 0 900 180 900'/%3E%3Cpolygon points='270 750 180 900 360 900'/%3E%3Cpolygon fill='%23DDD' points='270 750 360 600 180 600'/%3E%3Cpolygon points='450 750 540 600 360 600'/%3E%3Cpolygon points='630 750 540 900 720 900'/%3E%3Cpolygon fill='%23444' points='630 750 720 600 540 600'/%3E%3Cpolygon fill='%23AAA' points='810 750 720 900 900 900'/%3E%3Cpolygon fill='%23666' points='810 750 900 600 720 600'/%3E%3Cpolygon fill='%23999' points='990 750 900 900 1080 900'/%3E%3Cpolygon fill='%23999' points='180 0 90 150 270 150'/%3E%3Cpolygon fill='%23444' points='360 0 270 150 450 150'/%3E%3Cpolygon fill='%23FFF' points='540 0 450 150 630 150'/%3E%3Cpolygon points='900 0 810 150 990 150'/%3E%3Cpolygon fill='%23222' points='0 300 -90 450 90 450'/%3E%3Cpolygon fill='%23FFF' points='0 300 90 150 -90 150'/%3E%3Cpolygon fill='%23FFF' points='180 300 90 450 270 450'/%3E%3Cpolygon fill='%23666' points='180 300 270 150 90 150'/%3E%3Cpolygon fill='%23222' points='360 300 270 450 450 450'/%3E%3Cpolygon fill='%23FFF' points='360 300 450 150 270 150'/%3E%3Cpolygon fill='%23444' points='540 300 450 450 630 450'/%3E%3Cpolygon fill='%23222' points='540 300 630 150 450 150'/%3E%3Cpolygon fill='%23AAA' points='720 300 630 450 810 450'/%3E%3Cpolygon fill='%23666' points='720 300 810 150 630 150'/%3E%3Cpolygon fill='%23FFF' points='900 300 810 450 990 450'/%3E%3Cpolygon fill='%23999' points='900 300 990 150 810 150'/%3E%3Cpolygon points='0 600 -90 750 90 750'/%3E%3Cpolygon fill='%23666' points='0 600 90 450 -90 450'/%3E%3Cpolygon fill='%23AAA' points='180 600 90 750 270 750'/%3E%3Cpolygon fill='%23444' points='180 600 270 450 90 450'/%3E%3Cpolygon fill='%23444' points='360 600 270 750 450 750'/%3E%3Cpolygon fill='%23999' points='360 600 450 450 270 450'/%3E%3Cpolygon fill='%23666' points='540 600 630 450 450 450'/%3E%3Cpolygon fill='%23222' points='720 600 630 750 810 750'/%3E%3Cpolygon fill='%23FFF' points='900 600 810 750 990 750'/%3E%3Cpolygon fill='%23222' points='900 600 990 450 810 450'/%3E%3Cpolygon fill='%23DDD' points='0 900 90 750 -90 750'/%3E%3Cpolygon fill='%23444' points='180 900 270 750 90 750'/%3E%3Cpolygon fill='%23FFF' points='360 900 450 750 270 750'/%3E%3Cpolygon fill='%23AAA' points='540 900 630 750 450 750'/%3E%3Cpolygon fill='%23FFF' points='720 900 810 750 630 750'/%3E%3Cpolygon fill='%23222' points='900 900 990 750 810 750'/%3E%3Cpolygon fill='%23222' points='1080 300 990 450 1170 450'/%3E%3Cpolygon fill='%23FFF' points='1080 300 1170 150 990 150'/%3E%3Cpolygon points='1080 600 990 750 1170 750'/%3E%3Cpolygon fill='%23666' points='1080 600 1170 450 990 450'/%3E%3Cpolygon fill='%23DDD' points='1080 900 1170 750 990 750'/%3E%3C/g%3E%3C/pattern%3E%3C/defs%3E%3Crect x='0' y='0' fill='url(%23a)' width='100%25' height='100%25'/%3E%3Crect x='0' y='0' fill='url(%23b)' width='100%25' height='100%25'/%3E%3C/svg%3E");
background-attachment: fixed;
background-size: cover;
}
!

JS 

              
                const IDs = {
    canvas: 'canvas',
    shaders: {
        vertex: 'vertex-shader',
        fragment: 'fragment-shader'
    }
};



const CANVAS = document.getElementById(IDs.canvas);
const GL = canvas.getContext('webgl');

let PROGRAM;


main();


function main() {
    clearCanvas();
    createPlane();
    createProgram();
    createTexture();
    updateCanvasSize();
    initEventListeners();
    draw();
}


function clearCanvas() {
    GL.clearColor(0.26, 1, 0.93, 1.0);
    GL.clear(GL.COLOR_BUFFER_BIT);
}


function createPlane() {
    GL.bindBuffer(GL.ARRAY_BUFFER, GL.createBuffer());
    GL.bufferData(
        GL.ARRAY_BUFFER,
        new Float32Array([
            -1, -1,
            -1,  1,
             1, -1,
             1,  1
        ]),
        GL.STATIC_DRAW
    );
}


function createProgram() {
    const shaders = getShaders();

    PROGRAM = GL.createProgram();

    GL.attachShader(PROGRAM, shaders.vertex);
    GL.attachShader(PROGRAM, shaders.fragment);
    GL.linkProgram(PROGRAM);
    
    const vertexPositionAttribute = GL.getAttribLocation(PROGRAM, 'a_position');
    
    GL.enableVertexAttribArray(vertexPositionAttribute);
    GL.vertexAttribPointer(vertexPositionAttribute, 2, GL.FLOAT, false, 0, 0);

    GL.useProgram(PROGRAM);
}


function getShaders() {
    return {
        vertex: compileShader(
            GL.VERTEX_SHADER,
            document.getElementById(IDs.shaders.vertex).textContent
        ),
        fragment: compileShader(
            GL.FRAGMENT_SHADER,
            document.getElementById(IDs.shaders.fragment).textContent
        )
    };
}


function compileShader(type, source) {
    const shader = GL.createShader(type);

    GL.shaderSource(shader, source);
    GL.compileShader(shader);
    
    console.log(GL.getShaderInfoLog(shader));

    return shader;
}


function createTexture() {
    const image = new Image();

    image.crossOrigin = 'anonymous';

    image.onload = () => {
        const texture = GL.createTexture();
        
        GL.activeTexture(GL.TEXTURE0);
        GL.bindTexture(GL.TEXTURE_2D, texture);
        GL.pixelStorei(GL.UNPACK_FLIP_Y_WEBGL, true);
        GL.texImage2D(GL.TEXTURE_2D, 0, GL.RGB, GL.RGB, GL.UNSIGNED_BYTE, image);
        GL.texParameteri(GL.TEXTURE_2D, GL.TEXTURE_WRAP_S, GL.CLAMP_TO_EDGE);
        GL.texParameteri(GL.TEXTURE_2D, GL.TEXTURE_WRAP_T, GL.CLAMP_TO_EDGE);
        GL.texParameteri(GL.TEXTURE_2D, GL.TEXTURE_MIN_FILTER, GL.LINEAR);

        GL.uniform1i(GL.getUniformLocation(PROGRAM, 'u_texture'), 0);
    };

    // image.src = 'https://78.media.tumblr.com/b3c5e28fb0434e1e3f71f51085e06e54/tumblr_pea2d2SDUl1xujoc5o1_540.jpg';
    // Seems like tumblr has been blocked in Russia, so I changed the image to repair demos in my article.
    image.src = 'https://picsum.photos/id/502/1024/1024';
}




function updateCanvasSize() {
    const size = Math.ceil(Math.min(window.innerHeight, window.innerWidth) * .9) - 30;

    CANVAS.height = size;
    CANVAS.width = size;

    GL.viewport(0, 0, GL.canvas.width, GL.canvas.height);
    GL.uniform1f(GL.getUniformLocation(PROGRAM, 'u_canvas_size'),
            Math.max(CANVAS.height, CANVAS.width));
}


function initEventListeners() {
    window.addEventListener('resize', updateCanvasSize);

    document.addEventListener('mousemove', (e) => {
        let rect = CANVAS.getBoundingClientRect();

        MOUSE_POSITION = [
            e.clientX - rect.left,
            rect.height - (e.clientY - rect.top)
        ];

        GL.uniform2fv(GL.getUniformLocation(PROGRAM, 'u_mouse_position'), MOUSE_POSITION);
    });
}


function draw(timeStamp) {
    GL.uniform1f(GL.getUniformLocation(PROGRAM, 'u_time'), timeStamp / 1000.0);

    
    GL.drawArrays(GL.TRIANGLE_STRIP, 0, 4);

    requestAnimationFrame(draw);
}
!
999px

Console