:root { color-scheme: light; font-family: Arial, Helvetica, sans-serif; color: #202a35; background: #f5f8fb; }
* { box-sizing: border-box; }
body { margin: 0; line-height: 1.68; }
header, main, footer { width: min(100% - 2rem, 780px); margin-inline: auto; }
header { padding: 1.25rem 0; border-bottom: 1px solid #dce4ec; }
nav { display: flex; flex-wrap: wrap; gap: 1rem; }
nav a, a { color: #075985; }
main { padding: 2rem 0 3rem; }
h1, h2, h3 { color: #142b43; line-height: 1.25; }
h1 { font-size: clamp(2rem, 5vw, 3rem); margin: 0 0 .75rem; }
h2 { margin-top: 2.25rem; }
.eyebrow { color: #37556f; font-size: .9rem; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; }
.lead { color: #364a5e; font-size: 1.15rem; }
.worked, .practice, .check, .guide-card { margin: 1rem 0; padding: 1rem 1.25rem; border: 1px solid #cfdae5; border-radius: .65rem; background: #fff; }
.math { padding: .75rem 1rem; border-left: 4px solid #0b6b85; background: #eef6fa; font: 1.05rem/1.8 ui-monospace, SFMono-Regular, Consolas, monospace; overflow-wrap: anywhere; }
.small { color: #46596b; font-size: .95rem; }
footer { padding: 1.25rem 0 2rem; border-top: 1px solid #dce4ec; }
@media (max-width: 520px) { .worked, .practice, .check, .guide-card { padding: .85rem; } }