title: Shadow for rect in svg
body: <p>I need to make a shadow for <code>rect</code> element for <code>svg</code>. The  snippet below does the job, but I don't know how to control the <strong>color/opacity</strong> of the <strong>shadow</strong>? Any help will be appreciated!</p>
  
  <pre><code>&lt;svg height="120" width="120"&gt;
    &lt;defs&gt;
      &lt;filter id="f1" x="0" y="0" width="200%" height="200%"&gt;
        &lt;feOffset result="offOut" in="SourceGraphic" dx="20" dy="20" /&gt;
        &lt;feBlend in="SourceGraphic" in2="offOut" mode="normal" /&gt;
      &lt;/filter&gt;
    &lt;/defs&gt;
    &lt;rect width="90" height="90" stroke="green" stroke-width="3" fill="yellow" filter="url(#f1)" /&gt;
  </code></pre>