<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="style.css">
    <script type="module" defer src="main.js"></script>
    <title>Document</title>
</head>
<body>
    <canvas></canvas>

<script type="x-shader/x-fragment" id="vertShader">
    precision highp float;

    varying vec2 vUv;
    attribute vec2 a_position;

    varying vec2 vL;
    varying vec2 vR;
    var