#centro{
margin-left: 21%;
margin-top: 14%;
width: 50%;
height: auto;
background-color: rgba(0,0,0, 0.8);
border-radius: 6px 6px 6px 6px;
box-shadow: 1px 1px 10px 0px red inset;
color:red;
font-size: 130%;
padding: 1%;
position: relative;
z-index: 99;
}