What is the method for producing a radius that is opposite in direction for an element using css?

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The method for producing a radius that is opposite in direction for an element using CSS is to use the "border-radius" property and add the keyword "inset" before the values. This will create a border radius that goes inward, giving the appearance of the opposite direction. Example:

border-radius: inset 10px 5px 10px 5px;