html {
    box-sizing: border-box;
    font-size: 18px;
    --horz-gutter: 18px;
}

@media only screen and (min-width: 480px) {
    html {
        --horz-gutter: 36px;
    }
}

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

body {
    margin: 0;
}

main {
    padding: 0 var(--horz-gutter);
}

h1 {
    font-size: 2rem;
}

h2 {
    font-size: 1.5rem;
}

h3 {
    font-size: 1.25rem;
}

p, li {
    font-size: 1rem;
}