img     {display: block;
margin: 10px;
padding: 0 auto;
width: 100%;
height: auto;}
h1  {
    font-size: 50px;
    text-align: center;
}
body    {
    background-color: ivory;
}
.btn   {
display: inline-block;
background-color: gold;
color: white;
border-radius: 5px;
font-size: 20px;
font-weight: bolder;
text-decoration: none;
padding: 10px 20px;
}
.collection.box img {
    display: inline-block;
    vertical-align: middle;
    margin-right: 12px; /* spacing between images */
    max-width: 48%;      /* keeps images responsive and side-by-side */
    height: auto;
}

/* optional: prevent the h1 from sitting inline with the images */
.collection.box h1 {
    display: block;
    width: 100%;
    margin-bottom: 8px;
}