How Can I Create a Transparent Half-Circle Cutout in a Div Using Only CSS3?

Creating a Transparent Half-Circle Cut Out in a Div

Problem Statement:

Achieving a transparent half-circle shape cutout within a div using only CSS3, with the constraint that all elements forming the shape must be either black or transparent.

Solution:

To create the desired shape, we utilize the ::after pseudo-property of CSS:

body {
  background: green;
}

.rect {
  height: 100px;
  width: 100px;
  background: rgba(0, 0, 0, 0.5);
  position: relative;
  margin-top: 100px;
  margin-left: 100px;
}

.circle {
  display: block;
  width: 100px;
  height: 50px;
  top: -50px;
  left: 0;
  overflow: hidden;
  position: absolute;
}

.circle::after {
  content: '';
  width: 100px;
  height: 100px;
  -moz-border-radius: 100px;
  -webkit-border-radius: 100px;
  border-radius: 100px;
  background: rgba(0, 0, 0, 0);
  position: absolute;
  top: -100px;
  left: -40px;
  border: 40px solid rgba(0, 0, 0, 0.5);
}

HTML:

<div class="rect">
  <span class="circle"></span>
</div>

This solution creates an equilateral triangle containing a circle that is squeezed upwards so that the intersection forms a half-circle shape. By setting the background properties to black or transparent, we achieve the desired effect.

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