Two Rounding Values ​​for Different CSS Corners

If two values ​​are specified, the first value specifies the rounding for the upper left and lower right corners, the second value specifies the rounding for the upper right and lower left corners:

html<div id="elem"></div>

css#elem {
  width: 300px;
  height: 100px;
  border: 1px solid red;
  border-radius: 10px 40px;
}

Результат: