CSS font size using relative unit

font.css

html {
    font-size: 16px;
}

html * {
    font-size: 1rem;
}

h1 {
    font-size: 2rem;
}

h2 {
    font-size: 1.5rem;
}

h3 {
    font-size: 1.17rem;
}

h4 {
    font-size: 1rem;
}

h5 {
    font-size: .83rem;
}

h6 {
    font-size: .67rem;
}

h1,
h2,
h3,
h4,
h5,
h6 {
    margin: 0;
}

/*for screen size like iPhone5*/
@media only screen and (max-width: 350px) {
    html {
        font-size: 14px;
    }
}

/*涵蓋大部分系統之中文黑體*/
html,
body {
    font-family: 'Noto Sans CJK TC', 'PingFang', 'Microsoft JhengHei', sans-serif;
}