title: html canvas motion blur with transparent background
body: <p>I just created a fancy canvas effect using cheap motion blur</p>
  
  <pre><code>ctx.fillStyle = "rgba(255,255,255,0.2)";
  ctx.fillRect(0,0,canvas.width,canvas.height);
  </code></pre>
  
  <p>Now i want to do the same, but with transparent background. Is there any way to do something like that? I'm playing with globalAlpha, but this is probably a wrong way.</p>
  
  <p>PS: Google really don't like me today</p>