* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    line-height: 1.65;
    color: #24292e;
    background-color: #fcfcfc;
    padding: 2rem 1rem;
}

header, main {
    max-width: 650px;
    margin: 0 auto;
}

header {
    border-bottom: 1px solid #e1e4e8;
    padding-bottom: 1rem;
    margin-bottom: 2.5rem;
}

nav a {
    color: #0366d6;
    text-decoration: none;
    margin-right: 1.5rem;
    font-weight: 500;
}

nav a:hover {
    text-decoration: underline;
}

article h1 {
    font-size: 2rem;
    font-weight: 700;
    line-height: 1.25;
    margin-bottom: 1.5rem;
    color: #111;
}

article h2 {
    font-size: 1.5rem;
    font-weight: 600;
    margin-top: 2rem;
    margin-bottom: 1rem;
    color: #222;
}

article p {
    margin-bottom: 1.5rem;
    font-size: 1.1rem;
}

article ul, article ol {
    margin-bottom: 1.5rem;
    padding-left: 2rem;
}

article li {
    margin-bottom: 0.5rem;
}