How to add a shadow for the inverse with a radial gradient only around the edges?

Question

I am new to this thread and have not found anywhere how to apply a shadow to the back corners of type C.

Below is an image of an example for which I am trying to add a shadow only to the corners

Below is the code I used to achieve this reverse rounded corner:

CSS code:

div {
  background-color: #a9a8a8;
  background: -moz-radial-gradient(0 100%, circle, rgba(204, 0, 0, 0) 100px, #f7f6f6 15px), -moz-radial-gradient(100% 100%, circle, rgba(204, 0, 0, 0) 100px, #f7f6f6 15px), -moz-radial-gradient(100% 0, circle, rgba(204, 0, 0, 0) 100px, #f7f6f6 15px), -moz-radial-gradient(0 0, circle, rgba(204, 0, 0, 0) 100px, #f7f6f6 15px);
  background: -o-radial-gradient(0 100%, circle, rgba(204, 0, 0, 0) 100px, #f7f6f6 15px), -o-radial-gradient(100% 100%, circle, rgba(204, 0, 0, 0) 100px, #f7f6f6 15px), -o-radial-gradient(100% 0, circle, rgba(204, 0, 0, 0) 100px, #f7f6f6 15px), -o-radial-gradient(0 0, circle, rgba(204, 0, 0, 0) 100px, #f7f6f6 15px);
  background: -webkit-radial-gradient(0 100%, circle, rgba(204, 0, 0, 0) 100px, #f7f6f6 15px), -webkit-radial-gradient(100% 100%, circle, rgba(204, 0, 0, 0) 100px, #f7f6f6 15px), -webkit-radial-gradient(100% 0, circle, rgba(204, 0, 0, 0) 100px, #f7f6f6 15px), -webkit-radial-gradient(0 0, circle, rgba(204, 0, 0, 0) 100px, #f7f6f6 15px);
  background-position: bottom left, bottom right, top right, top left;
  -moz-background-size: 50% 50%;
  -webkit-background-size: 50% 50%;
  background-size: 50% 50%;
  background-repeat: no-repeat;
  height: 300px;
  width: 500px;
}

<div></div>

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So now I want to add the shadow effect only to the rounded corners of the gray gray section. I want to illustrate the effect as light gray on top of gray.

Answer 1

radial-gradient, , , , .

( ):

radial-gradient(circle at 0 100%, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px)

:

• rgba(204, 0, 0, 0) 100px . C ( ).
• 100px 104px rgba(204, 0, 0, 0) #AAA ( ), . , .
• 104px 105px , #AAA #f7f6f6, .

div {
  background: -moz-radial-gradient(0 100%, circle, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px), -moz-radial-gradient(100% 100%, circle, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px), -moz-radial-gradient(100% 0, circle, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px), -moz-radial-gradient(0 0, circle, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px);
  background: -webkit-radial-gradient(0 100%, circle, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px), -webkit-radial-gradient(100% 100%, circle, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px), -webkit-radial-gradient(100% 0, circle, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px), -webkit-radial-gradient(0 0, circle, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px);
  background: radial-gradient(circle at 0 100%, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px), radial-gradient(circle at 100% 100%, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px), radial-gradient(circle at 100% 0, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px), radial-gradient(circle at 0 0, rgba(204, 0, 0, 0) 100px, #AAA 104px, #f7f6f6 105px);
  background-position: bottom left, bottom right, top right, top left;
  background-size: 50% 50%;
  background-repeat: no-repeat;
  height: 300px;
  width: 500px;
}

<div></div>

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---

, , , . , :

div {
  background: -moz-radial-gradient(0 100%, circle, rgb(168, 168, 168) 100px, rgb(139, 139, 139) 102px, rgb(139, 139, 139) 106px, rgb(246, 246, 246) 106px), -moz-radial-gradient(100% 100%, circle, rgb(168, 168, 168) 100px, rgb(139, 139, 139) 102px, rgb(139, 139, 139) 106px, rgb(246, 246, 246) 106px), -moz-radial-gradient(100% 0, circle, rgb(168, 168, 168) 100px, rgb(139, 139, 139) 102px, rgb(139, 139, 139) 106px, rgb(246, 246, 246) 106px), -moz-radial-gradient(0 0, circle, rgb(168, 168, 168) 100px, rgb(139, 139, 139) 102px, rgb(139, 139, 139) 106px, rgb(246, 246, 246) 106px);
  background: -webkit-radial-gradient(0 100%, circle, rgb(168, 168, 168) 100px, rgb(139, 139, 139) 102px, rgb(139, 139, 139) 106px, rgb(246, 246, 246) 106px), -webkit-radial-gradient(100% 100%, circle, rgb(168, 168, 168) 100px, rgb(139, 139, 139) 102px, rgb(139, 139, 139) 106px, rgb(246, 246, 246) 106px), -webkit-radial-gradient(100% 0, circle, rgb(168, 168, 168) 100px, rgb(139, 139, 139) 102px, rgb(139, 139, 139) 106px, rgb(246, 246, 246) 106px), -webkit-radial-gradient(0 0, circle, rgb(168, 168, 168) 100px, rgb(139, 139, 139) 102px, rgb(139, 139, 139) 106px, rgb(246, 246, 246) 106px);
  background: radial-gradient(circle at 0 100%, rgb(168, 168, 168) 100px, rgb(139, 139, 139) 102px, rgb(139, 139, 139) 106px, rgb(246, 246, 246) 106px), radial-gradient(circle at 100% 100%, rgb(168, 168, 168) 100px, rgb(139, 139, 139) 102px, rgb(139, 139, 139) 106px, rgb(246, 246, 246) 106px), radial-gradient(circle at 100% 0, rgb(168, 168, 168) 100px, rgb(139, 139, 139) 102px, rgb(139, 139, 139) 106px, rgb(246, 246, 246) 106px), radial-gradient(circle at 0 0, rgb(168, 168, 168) 100px, rgb(139, 139, 139) 102px, rgb(139, 139, 139) 106px, rgb(246, 246, 246) 106px);
  background-position: bottom left, bottom right, top right, top left;
  background-size: 50% 50%;
  background-repeat: no-repeat;
  height: 300px;
  width: 600px;
}

<div></div>

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Answer 2

, 4 .
.
box-shadow: 0px 0px |amount-of-blur|length-of-shaodw| color
box-shadow: 0px 0px 60px 50px black

body {
  background-color: #222;
}
.corner-shadow {
  position: relative;
  width: 500px;
  height: 300px;
  background-color: white;
  overflow: hidden;
}
.corner-shadow .corner {
  position: absolute;
  border-radius: 50%;
  width: 2px;
  height: 2px;
  box-shadow: 0px 0px 60px 50px black;
}
.corner.top {
  top: -2px;
}
.corner.left {
  left: -2px;
}
.corner.right {
  right: -2px;
}
.corner.bottom {
  bottom: -2px;
}

<div class="corner-shadow">
  <div class="corner top left"></div>
  <div class="corner top right"></div>
  <div class="corner bottom left"></div>
  <div class="corner bottom right"></div>
</div>

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