div{
    width: 80%;
    height: 120px;
    border: 2px solid #333;
    margin: 10px auto;
}

#ex1{
    background:radial-gradient(
	closest-side circle, yellow, green, purple);
}
#ex2{
    background:radial-gradient(
	100px circle at top, yellow, green, purple);
}
#ex3{
    background:radial-gradient(
	100px 50px at 25% 50%, 
	yellow 40%, green 60%, purple);
}

/*Déclaration aberrante*/
#ex4{
    background:radial-gradient(
	100px 50px circle at 25% 50%, 
	yellow, green, purple);
}