| <svg xmlns="http://www.w3.org/2000/svg"> | |
| <mask id="mask" mask-type="alpha"> | |
| <rect width="200" height="200" fill="black" opacity="0"/> | |
| <rect x="50" y="50" width="100" height="100" fill="black"/> | |
| </mask> | |
| <rect width="200" height="200" fill="green" mask="url(#mask)"/> | |
| </svg> |
