.kuroback-shiromoji {
    display: inline-block;
    background-color: black; 
    color: white; 
    font-size: calc(14px + 4px); 
    margin: 4px 0; 
    padding: 4px; 
    text-align: center; 
    font-weight: bold; /* 文字をボールドにする指定 */
}
.circle {
    display: inline-flex;
    justify-content: center;
    align-items: center;
    width: 38px;
    height: 38px;
    background-color: black;
    color: white;
    font-weight: bold;
    border-radius: 50%;
    font-size: 16px;
    line-height: 1;
    font-family: 'Arial', sans-serif;
    vertical-align: middle;
}

/*
.kuroback::before {
    content: "\00a0";
}

.kuroback::after {
    content: "\00a0";
}