Try it Live - HTML5 SVG Mask

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<!DOCTYPE html>
<html>
  <body>
    <h2>Example of SVG Mask </h2>
    <svg>
      <defs>
        <mask id="myMask">
          <rect x="0" y="0" width="200" height="200" fill="white" />
          <polygon points="150,130 20,30 100,30" fill="brown" />
        </mask>
      </defs>
      <polygon points="15 13, 120 38, 60 100, 20 10, 13 58" fill="crimson" />
      <circle cx="50" cy="50" r="50" mask="url(#myMask)" />
    </svg>
  </body>
</html>
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