* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body, html {
    height: 100%;
    font-family: sans-serif;
}

.container {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100%;
    position: relative;
}

.container::before {
    content: "";
    position: absolute;
    width: 100px;
    height: 100px;
    background: radial-gradient(circle, #c9c9c9 0%, white 50%);
    border-radius: 50%;
    z-index: -1;
    animation: pulse 60s linear infinite;
}

@keyframes pulse {
    0%, 100% {
        width: 100px;
        height: 100px;
    }
    50% {
        width: 100vmin;
        height: 100vmin;
    }
}

h1 {
    position: relative;
    z-index: 1;
}