How do I create a circle using CSS with only width, height, border, and border-radius properties?

<br>div {</p>
<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">width: 0;
height: 0;
border: 180px solid red;
border-radius: 180px;

}

• width and height: These properties define the dimensions of the box, initially set to zero. As a result, there's no actual content area.
• border: This property creates a border around the box, with a width of 180 pixels and color red.
• border-radius: Crucially, this property assigns a radius of 180 pixels to the corners of the border.

Understanding the Result

Height and Width Applied to Content:
In CSS, the height and width properties typically apply to the content area of an element. Since our width and height are set to zero, the border effectively becomes the only visible part of the element.

Border-Radius Applied to Border:
The border-radius property doesn't directly apply to the content area. Instead, it operates on the border edges. In this case, the border width is 180 pixels, while the border-radius is also 180 pixels.

Result: A Circle emerges
This combination of border-radius and border width creates a unique effect. The border forms a square due to the zero width and height, but the 180 pixels radius curves all its corners so drastically that it resembles a circle.

Further Observations

• Smaller border-radius values, relative to the border width, result in more square-like shapes.
• Increasing the border-radius while keeping the border width the same makes the circle more prominent.
• Adjusting the border colors and widths can further customize the appearance of the circle.

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