1-A 2-A 3-A 4-A | 5 width 6 root/html 7 = <meta name="viewport" content="width=device-width, initial-scale=1"> 8 = @media (max-width:700px){ .row { flex-direction:column; } } 9 = Most traffic is mobile; simpler base styles enhanced upward | 10 = px fixed; rem scales with user font settings (accessible)