*{
	box-sizing: border-box;
}
div.columna{
	float: left;
	width: 25%;
	height: 200px;
	padding: 20px;
	background-color: aqua;
	overflow: hidden;


}
@media screen and (max-width: 781px){
	div.columna{
	float: left;
	width: 50%;
	height: 200px;
	padding: 20px;
	background-color: tomato;
	overflow: hidden;

}
@media screen and (max-width: 581px){
	div.columna{
	float: left;
	width: 100%;
	height: 200px;
	padding: 20px;
	background-color: orange;
	overflow: hidden;
}