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                <p>Swipe to see animation</p>
<canvas id="web-gl" width="300" height="300"></canvas>
<script id="vert-shader" type="x-shader/x-vertex">
attribute vec2 aVertexPosition;

uniform mat2 scaleMatrix;
uniform mat2 rotationMatrix;

varying vec4 pixelPosition;

void main() {
  // gl_Position is a special variable a vertex shader is responsible for setting
  gl_Position = vec4(scaleMatrix * rotationMatrix * aVertexPosition, 0.0, 1.0);
  // interpolated pixel position
  pixelPosition = vec4(aVertexPosition, 0.0, 1.0);
<script id="frag-shader" type="x-shader/x-fragment">
// Set the default precision
precision highp float;
uniform mat2 rotationMatrix;
varying vec4 pixelPosition;
void main() {
    vec3 color = vec3((pixelPosition.x + 1.0) / 2.0, 0.0, 0.5);
    gl_FragColor = vec4(color, 1.0);


                body, html {
	display: flex;
	flex-direction: column;
	justify-content: center;
	height: 100%;
	align-items: center;
	font-family: Arial, sans-serif;
	color: #ddd;
	text-transform: uppercase;

canvas {
    border-radius: 30px;
    box-shadow: 0px 20px 30px -10px #00000047;


                let canvas;
let gl;
let program;
let vertexBuffer;
let vertexCount;
let scale = 0.5;
let theta = 0;
const vertexNumComponents = 2;

// Load Shaders
let vertexSource = document.getElementById("vert-shader").textContent
let fragmentSource = document.getElementById("frag-shader").textContent

setup(vertexSource, fragmentSource);

// Setup WebGl environment
function setup(vertexSource, fragmentSource) {

    // Initialize canvas and webgl context
    canvas = document.getElementById("web-gl");
    gl = canvas.getContext("webgl");

    // Compile both shaders
    const vertexShader = gl.createShader(gl.VERTEX_SHADER);
    gl.shaderSource(vertexShader, vertexSource);
    if (!gl.getShaderParameter(vertexShader, gl.COMPILE_STATUS))
        console.log(gl.getShaderInfoLog(vertexShader)); // Log the error if GLSL fails to compile

    const fragmentShader = gl.createShader(gl.FRAGMENT_SHADER);
    gl.shaderSource(fragmentShader, fragmentSource);
    if (!gl.getShaderParameter(fragmentShader, gl.COMPILE_STATUS))
        console.log(gl.getShaderInfoLog(fragmentShader)); // Log the error if GLSL fails to compile

    // Create WebGL Program
    program = gl.createProgram();
    gl.attachShader(program, vertexShader);
    gl.attachShader(program, fragmentShader);
    if (!gl.getProgramParameter(program, gl.LINK_STATUS))

    // Create shape
    const vertices = [
        -1.0, -1.0,
         1.0, -1.0,
         1.0,  1.0,
        -1.0, -1.0,
         1.0,  1.0,
        -1.0,  1.0,
    vertexCount = vertices.length / vertexNumComponents;

    vertexBuffer = gl.createBuffer();
    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(vertices), gl.STATIC_DRAW); // set float32 if doesnt work

  // Set rotation based on mouse position
  const setRot = e => theta = 2 * 3.145 * e.pageX / innerWidth;
  const setRotTouch = e => theta = 2 * 3.145 * e.touches[0].pageX / innerWidth;
  document.addEventListener("mousemove", setRot);
  document.addEventListener("touchmove", setRotTouch);

function run() {
    gl.viewport(0, 0, canvas.width, canvas.height);
    gl.clearColor(0.8, 0.9, 1.0, 1.0);


    gl.bindBuffer(gl.ARRAY_BUFFER, vertexBuffer);

    // Tranformation Matrices
    const S = [scale, 0, 0, scale]
    const R = [Math.cos(theta), -Math.sin(theta), Math.sin(theta), Math.cos(theta)]
    gl.uniformMatrix2fv( gl.getUniformLocation(program, "scaleMatrix"), false, S );
    gl.uniformMatrix2fv( gl.getUniformLocation(program, "rotationMatrix"), false, R );
    // Load square to Vertex Shader (aka Draw)
    const aVertexPosition = gl.getAttribLocation(program, "aVertexPosition");
    gl.vertexAttribPointer(aVertexPosition, vertexNumComponents, gl.FLOAT, false, 0, 0);
    gl.drawArrays(gl.TRIANGLES, 0, vertexCount);