<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>随机多边形</title>
  <script src="../common/lib/gl-renderer.js"></script>
</head>
<body>
  <canvas width="600" height="600"></canvas>
  <script>
    const canvas = document.querySelector('canvas');
    const renderer = new GlRenderer(canvas);

    const vertex = `
      attribute vec2 a_vertexPosition;
      
      void main() {
        gl_Position = vec4(a_