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

body{
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100vh;
    background-color: rgba(89,153,231,0.5);
    position: relative;
    /* はみ出た要素を隠す＝スクロール出来なくさせる */
    overflow: hidden;
}

h2{
    position: relative;
    z-index: 100;
    color: white;
    font-size: 5rem;
}

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

.block{
    position: absolute;
    width: 100px;
    height: 100px;
    border-radius: 50%;
    background-color: rgba(70, 149, 70, 0.764);
    box-shadow: 10px 10px 50px rgba(0,0,0,0.2);
}