پارامتر shape در شیب رنگ

#grad
{
background: -webkit-radial-gradient(circle, red, yellow, green); /* Safari */
background: -o-radial-gradient(circle, red, yellow, green); /* Opera 11.1 to 12.0 */
background: -moz-radial-gradient(circle, red, yellow, green); /* Firefox 3.6 to 15 */
background: radial-gradient(circle, red, yellow, green); /* Standard syntax */
}