html {
    box-sizing: border-box;
}

*, *:before, *:after {
    box-sizing: inherit;
}

body {
    font-size: 16px;
    font-family: arial, helvetica, sans-serif;
    padding-left: 2em;
    padding-right: 2em;
}

main {
    max-width: 72ch;
    margin: 0 auto;
}

ol {
    margin-bottom: 2em;
}

li ul {
    margin-top: 0.5em;
}

li + li {
    margin-top: 0.5em;
}