studies.css

body {
    background: rgb(26, 53, 79);
    color: rgb(45, 45, 45);
    padding: 10px;
    font-family: arial;
}
header {
    font-size: 1.5em;
    font-weight: bold;
}
[id=all-contents] {
    max-width: 800px;
    margin: auto;
}

/* navigation menu */
nav {
    background: rgb(89, 27, 44);
    margin: 0 auto;
    display: flex;
    padding: 10px;
}
nav header {
    display: flex;
    align-items: center;
    color: rgb(255, 255, 255);
    flex: 1;
}
nav ul {
    list-style-image: none;
}
nav li {
    display: inline-block;
    padding: 0 10px;
}
nav a {
    text-decoration: none;
    color: #fff;
}

/* main container area beneath menu */
main {
    background: rgb(242, 171, 190);
    display: flex;
    padding:inherit;
}
[class=content] {
    flex: 1;
    border-radius:35px;
    padding: 15px;
    margin-top:15px;
    box-sizing: border-box;
    width: 100%;
}

.content h1, h2, h3, h4, h5, h6 {
    margin: 10px;
}

.content section > a {
    text-decoration: none;
}

.code {
    font-family: monospace;
    background: #eee;
    border: 1px solid #ccc;
    color: #222;
    white-space: pre;
    width: 100%;
    margin-bottom: 20px;
    overflow: scroll;
}

.topic-heading {
    padding-left: 50px;
    text-transform: capitalize;
}

.line {
    display: flex;
    padding: 2px 0;
}

.line:nth-child(even) {
    background: #ddd;
}

.line-number {
    min-width: 40px;
    padding-left: 5px;
    text-align: right;
    padding-right: 20px;
}