body {
    margin: 0;
    padding: 0;
    background: url(background.jpg)no-repeat;
    background-size: cover;
}

.loader {
    background: #111;
    width: 100%;
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
}

.loader div {
    background: #fff;
    width: 16px;
    height: 32px;
    margin-left: 10px;
    animation: loader 1.2s infinite;
}

@keyframes loader {
    50% {
        height: 64px;
    }
}

.loader div:nth-child(1) {
    background: #585858;
    animation-delay: -0.40s;
}

.loader div:nth-child(2) {
    background: #bdbdbd;
    animation-delay: -0.20s;
}

.loader div:nth-child(3) {
    background: #ffffff;
    animation-delay: 0s;
}