demo.svg

<?xml version="1.0"?>
<svg viewBox="-7.5 -7.5 15 15"
  version="1.1" xmlns="http://www.w3.org/2000/svg">
  <circle cx="0" cy="0" r="7.0710678118654755" fill="grey"/><!-- r = 5*sqrt(2) -->
  <rect id="S" x="-5" y="-5" width="10" height="10"/>
  <rect x="5" y="-1" width="2" height="2"/>
  <rect x="-1" y="-7" width="2" height="2"/>
  <rect x="-1" y="5" width="2" height="2"/>
  <rect x="-7" y="-1" width="2" height="2"/>
  <polygon points="0,0 7,0 7,-1"/>
  <line class="axis" x1="0" x2="0" y1="-8" y2="8"/>
  <line class="axis" y1="0" y2="0" x1="-8" x2="8"/>
  <style><![CDATA[
    circle { fill: grey; }
    rect#S { fill: lightgrey; }
    rect { fill: darkgrey; }
    polygon {
      fill: blue;
      fill-opacity: 0.25;
      stroke: black;
      stroke-width: 0.02;
      stroke-dasharray: 0.1, 0.1;
    }
    .axis {
      stroke: black;
      stroke-width: 0.02;
      stroke-opacity: 0.5;
    }
  ]]></style>
</svg>