body{
    width: 100%;
    vertical-align: middle;
    display: inline-block;
    background-position: middle;
    background-size: cover;
    background-image: url("images/im1.png");
    text-align: center;
    margin-top: 200px;
}
@media screen and (min-width: 800px) {
body{
    margin-top: 200px;
}
body .celda{
    background: #fff;
    width: 40%;
    display: inline-block;
    text-align: center;
    padding: 20px 40px;
    border-radius: 10px;
    border: none;
}
body .celda img{
    width: 80%;
    display: inline-block;
}
body .celda a{
    background: #ffbb00;
    padding: 10px 20px;
    font-size: 20px;
    font-weight: bold;
    text-decoration: none;
    color: #fff;
    border-radius: 5px;
    transition: 400ms;
}
body .celda a:hover{
    background: #b88701;
    transition: 400ms;
}
}
@media screen and (max-width: 800px) {
    body{
        margin-top: 150px;
        background-image: url("images/im2.png");
    }
    body .celda{
        background: #fff;
        width: 80%;
        display: inline-block;
        text-align: center;
        padding: 20px 10px;
        border-radius: 10px;
        border: none;
    }
    body .celda img{
        width: 80%;
        display: inline-block;
        margin-bottom: 15px;
    }
    body .celda a{
        background: #ffbb00;
        padding: 10px 20px;
        font-size: 20px;
        font-weight: bold;
        text-decoration: none;
        color: #fff;
        border-radius: 5px;
        transition: 400ms;
        width: 80%;
        display: inline-block;
    }
    body .celda a:hover{
        background: #b88701;
        transition: 400ms;
    }
    }