I want to place a rect element inside another rect element. I used opacity, but it always shows me a rectangle. I used the following code:
<svg width="400" height="180">
<g>
<rect x="50" y="20" width="150" height="150" style="fill:black;stroke:black;stroke-width:2;fill-opacity:0;stroke-opacity:1;">
<rect x=50 y=30 width=50 height=50>
</g>
</svg>