html, body {
    margin: 0;
    padding: 0;
    background: black;
}

:root {
    --white: #FFFFFF;
    --red: #BC022C;
    --flag-height: 300px;
}

.flag-japan{
    background: var(--white);
    height: var(--flag-height);
    width: calc(var(--flag-height) * 3/2);
    margin: 30px auto;
    display: flex;
    justify-content:center;
    align-items: center;
    
}

.circle{
    background: var(--red);
    height: calc(var(--flag-height) * 3/5);
    width: calc(var(--flag-height) * 3/5);
    border-radius: 50%;
    

}