How Can I Create a Transparent Half-Circle Cutout Using Only CSS3?
Dec 27, 2024 pm 04:53 PM
Creating a Transparent Half-Circle Cutout with CSS3
To achieve the desired transparent half-circle shape, where all elements remain black or transparent, a technique utilizing the CSS ::after pseudo property can be employed.
The trick lies in the clever combination of a black rectangle and a circle. The rectangle serves as the base, providing the black background. Over this, a circle is positioned absolutely and partially hidden using the overflow property.
Key to this technique is the ::after pseudo element added to the circle. With its width and height set to 100px, it forms a perfect semi-circle. A 40px-thick border is applied, but the background remains transparent.
By adjusting the position of the ::after pseudo element, the semi-circle can be shifted upwards to align with the edge of the rectangle, creating the illusion of a cut-out.
Here's an example code that demonstrates this technique:
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);
}
<div class="rect"> <span class="circle"></span> </div>
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