Responsive Dribbble Shots Grid

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">

CSS

body {
    margin: 0;
    background: #eee;
}
form {
    padding: 10px;
    background: #333;
    text-align: center;
}

#list {
    padding: 10px 0 0 10px;
    max-width: 1200px;
    margin: 0 auto;
    transition: all .2s;
}
#list a {
    position: relative;
    float: left;
    width: 100%;
    padding: 0 10px 10px 0;
    transition: all .2s;
}
#list a img {
    position: relative;
    display: block;
    width: 100%;
    box-shadow: 2px 2px 5px rgba(0,0,0,.25);
}

.form-group:last-child {
    margin-bottom: 0;
}

footer {
    margin: 10px 0;
    text-align: center;
    font-style: italic;
    font-size: 12px;
    color: #666;
}
footer a {
    color: #ea4c89 !important;
}

@media (min-width: 500px) {
    #list a { width: 50%; }
}
@media (min-width: 768px) {
    #list {
        padding: 20px 0 0 20px;
    }
    #list a {
        width: 25%;
        padding: 0 20px 20px 0;
    }
}