body {
    background-color: skyblue;
}

.example-wrapper { 
    margin: 1em auto; 
    max-width: 1200px; 
    width: 95%; 
    font: 18px/1.5 sans-serif; 
}

.example-wrapper code { 
    background: #F5F5F5; 
    padding: 2px 6px; 
}

.card-img-top {
    width: 100%;
    height: 8em;
    background: lightgrey;
    display: flex;
    align-items: center;
    justify-content:center;
}