<!DOCTYPE html>
<html>
<head>
  <style type="text/css">
    #backdrop {
      float: left;
      width: 512px;
      height: 512px;
      isolation: isolate;
      background-image: linear-gradient(to bottom,
          rgba(255, 255, 0, 0.9),
          rgba(255, 0, 0, 0.9),
          rgba(0, 255, 0, 0.9),
          rgba(0, 0, 255, 0.9),
          rgba(0, 0, 0, 0.9));
      position: absolute;
      top: 100px;
      left: 100px;
    }

    #backdrop div {
      position: absolute;
      width: 100%;
      h