body {
    background: #444;
}

.main {
    font-size: 40px;
    color: #fff;
}

.square {
    display: flex;
    height: 100px;
    width: 900px;
    border-radius: 30px;
    background: #cccccc;
    position: fixed;
    left: 50%;
    right: 50px;
    bottom: 100px;
}

.circle {
    height: 100px;
    width: 100px;
    background: red;
    border-radius: 100%;
    position: relative;
    left: 100px;
    bottom: 50%;
}