styleCss.css

@import url(https://fonts.googleapis.com/css?family=Muli:400,300);

body,
html {
    min-height: 100%;
    height: 100%;
}

body {
    display: flex;
    align-items: center;
    justify-content: center;
    color: #ccc;
    font-family: Muli, sans-serif;
    background-image: url('https://media.giphy.com/media/WVgOHto4Packo/giphy.gif');
    background-position: center;
    background-size: cover;
    &:before,
    &:after {
        content: "";
        position: absolute;
    }
    &:before {
        top: 5%;
        right: 5%;
        bottom: 5%;
        left: 5%;
        z-index: -1;
        background-size: cover;
        background-position: top center;
        background-image: url('https://media.giphy.com/media/WVgOHto4Packo/giphy.gif');
        filter: blur(5px);
        overflow: hidden;
    }
    &:after {
        top: 5%;
        right: 5%;
        bottom: 5%;
        left: 5%;
        border: 1px solid #fefefe;
        background: rgba(#000, 0.6);
        mix-blend-mode: overlay;
        z-index: -1;
    }
}

.four-oh-four {
    text-align: center;
    padding: 0 4%;
    a {
        display: inline-block;
        margin: 10px 0;
        padding: 10px 20px;
        color: #fefefe;
        font-weight: 300;
        text-decoration: none;
        border: 1px solid #fefefe;
    }
}

h1 {
    margin: 0;
    font-size: 3em;
    letter-spacing: -1px;
}