CSS의 텍스트 줄에 패딩을 추가하는 방법은 무엇입니까?

#titleContainer {
    width: 520px;
}

h3 {
    margin: 0;
    font-size: 42px;
    font-weight: bold;
    font-family: sans-serif;
}

/* Styling for main text line */
h3 .heading {
    background-color: #000;
    color: #00a3d0;
}

/* Styling for subhead line */
h3 .subhead {
    background-color: #00a3d0;
    color: #000;
}

/* Container for line separation */
div {
    line-height: 1.1;
    padding: 1px 0;
    border-left: 30px solid #000;
    display: inline-block;
}

/* Positioning of main text line */
h3 {
    background-color: #000;
    color: #fff;
    display: inline;
    margin: 0;
    padding: 0;
}

/* Indentation for subhead line */
h3 .indent {
    position: relative;
    left: -15px;
}

/* Adjustments for subhead line */
h3 .subhead {
    padding: 0 15px;
    float: left;
    margin: 3px 0 0 -29px;
    outline: 1px solid #00a3d0;
    line-height: 1.15;
}

<div>