<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>案例4 进度条</title>
    <style>
      body {
        display: flex;
        flex-direction: column;
        justify-content: center;
        align-items: center;
        height: 95vh;
      }
      .wrap {
        display: flex;
        justify-content: center;
        align-items: center;
        height: 100vh;
      }
      canvas {
        fl