html { background: url("https://img4.goodfon.com/wallpaper/nbig/2/39/tokho-toukhou-devushka-fon-mech.jpg") no-repeat center center fixed; -webkit-background-size: cover; -moz-background-size: cover; -o-background-size: cover; background-size: cover; } .card { opacity: 0.9; } .blurry { backdrop-filter: blur(7px) !important; } pre code { background-color: #eee; border: 1px solid #999; display: block; padding: 20px; }