JSFiddle - React, Tailwind, and code Playground

by Bateman

HTML

<div style="width:100px;height:100px;border:4px solid black;box-shadow:inset 0 0 30px black;margin:10px;"></div>
<svg>
    <defs>
        <filter id="drop-shadow">
            <feGaussianBlur in="SourceAlpha" result="blur" stdDeviation="5" />
            <feGaussianBlur in="SourceAlpha" result="blur2" stdDeviation="10" />
            <feGaussianBlur in="SourceAlpha" result="blur3" stdDeviation="15" />
            <feMerge>
                <feMergeNode in="blur" mode="normal"/>
                <feMergeNode in="blur2" mode="normal"/>
                <feMergeNode in="blur3" mode="normal"/>
                <feMergeNode in="SourceGraphic" mode="normal"/>
            </feMerge>
        </filter>
    </defs>
    <rect x="10" y="10" width="100" height="100"
    stroke="black" stroke-width="4" fill="transparent" filter="url(#drop-shadow)"/>
</svg>
<svg style="border: thin solid;">
   <filter id="inset-shadow" x="-50%" y="-50%" width="200%" height="200%">
    <feComponentTransfer in=SourceAlpha>
      <feFuncA type="table" tableValues="1 0" />
    </feComponentTransfer>
    <feGaussianBlur stdDeviation="3"/>
    <feOffset dx="5" dy="5" result="offsetblur"/>
    <feFlood flood-color="rgb(20, 0, 0)" result="color"/>
    <feComposite in2="offsetblur" operator="in"/>
    <feComposite in2="SourceAlpha" operator="in" />
    <feMerge>
      <feMergeNode in="SourceGraphic" />
      <feMergeNode />
    </feMerge>
  </filter> 
  <circle cx=50 cy=50 r=20 fill=red filter="url(#inset-shadow)" />
</svg>