:root {
  --ground: #f2f4f7;
  --surface: #fff;
  --raised: #e9edf2;
  --ink: #17191c;
  --muted: #5e6670;
  --border: #d6dce3;
  --accent: #1d5fbf;
  --warning: #704710;
  --warning-soft: #f6f2e9;
  --radius: 8px;
}
* { box-sizing: border-box; }
html { color-scheme: light; scroll-padding-top: 24px; }
body { margin: 0; background: var(--ground); color: var(--ink); font: 16px/1.55 system-ui, -apple-system, "Segoe UI", sans-serif; }
a { color: inherit; text-underline-offset: 4px; }
a:hover { text-decoration-thickness: 2px; }
a:focus-visible, summary:focus-visible { outline: 3px solid var(--accent); outline-offset: 5px; border-radius: 2px; }
.wrap { width: min(1100px, calc(100% - 64px)); margin-inline: auto; }
.skip { position: absolute; left: 16px; top: -100px; background: var(--surface); padding: 12px 20px; z-index: 2; }
.skip:focus { top: 12px; }
.masthead { min-height: 88px; display: flex; align-items: center; justify-content: space-between; gap: 24px; }
.brand { display: inline-flex; align-items: center; gap: 12px; font-size: 17px; font-weight: 700; text-decoration: none; }
.mark { display: inline-flex; align-items: baseline; font-size: 32px; font-weight: 800; line-height: 1; letter-spacing: -5px; color: var(--accent); margin-right: 5px; }
.mark span { font-size: 22px; }
.sign-in { padding-block: 12px; font-size: 14px; font-weight: 600; }
.sign-in span { margin-left: 8px; }
.intro { padding: 36px 0 32px; }
h1 { margin: 0; font: 700 clamp(30px, 4.3vw, 48px)/1.12 Georgia, "Times New Roman", serif; letter-spacing: -.035em; }
.intro p { max-width: 65ch; margin: 20px 0 0; color: var(--muted); font-size: 17px; }
h2 { margin: 0; font-size: 20px; line-height: 1.3; letter-spacing: -.015em; }
p { margin: 12px 0 20px; }
/* 12 columns: (1100px - 11 * 16px) / 12 = 77px. Entries span 6 or 4 columns. */
.start-grid { display: grid; grid-template-columns: repeat(12, minmax(0, 1fr)); gap: 16px; }
.start-panel { grid-column: span 6; padding: 26px; background: var(--surface); border-radius: var(--radius); display: flex; flex-direction: column; align-items: flex-start; }
.start-panel p { max-width: 48ch; flex: 1; }
.section-title { display: flex; flex-wrap: wrap; gap: 10px 16px; align-items: center; }
.stage { display: inline-block; padding: 3px 8px; color: var(--warning); background: var(--warning-soft); font-size: 12px; font-weight: 650; border-radius: 4px; }
.button { display: inline-flex; align-items: center; justify-content: space-between; gap: 28px; padding: 11px 18px; min-height: 46px; background: var(--ink); color: var(--surface); border-radius: 6px; font-weight: 650; text-decoration: none; }
.button:hover { background: var(--muted); }
.text-action { display: inline-flex; align-items: center; gap: 12px; min-height: 46px; font-weight: 650; }
.parent-area { margin-top: 36px; }
.section-heading { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 8px 24px; align-items: baseline; margin-bottom: 16px; }
.section-heading p { font-size: 14px; color: var(--muted); margin: 0; }
.link-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 0 24px; }
.link-grid a { display: flex; justify-content: space-between; gap: 12px; padding: 17px 0; border-top: 1px solid var(--border); text-decoration: none; }
.link-grid a:hover strong { text-decoration: underline; text-underline-offset: 4px; }
.link-grid small { display: block; margin-top: 4px; color: var(--muted); font-size: 14px; }
.link-grid strong { font-size: 16px; font-weight: 650; }
.link-grid a > span:last-child { color: var(--muted); }
.math-area { margin-top: 28px; padding: 26px; background: var(--surface); border-radius: var(--radius); }
.math-heading { display: flex; align-items: center; flex-wrap: wrap; gap: 12px 16px; }
.math-content { display: grid; grid-template-columns: 1fr 1fr; gap: 32px; }
.math-content p { margin-bottom: 0; max-width: 55ch; }
.math-links { display: flex; flex-direction: column; align-items: flex-start; gap: 4px; }
.math-links > a:last-child { padding-block: 8px; font-size: 14px; }
.note { font-size: 14px; color: var(--muted); margin-bottom: 0; }
details { border-top: 1px solid var(--border); margin-top: 22px; padding-top: 8px; }
summary { cursor: pointer; min-height: 44px; padding-block: 10px; font-weight: 600; }
details p { font-size: 14px; color: var(--muted); margin: 4px 0; }
.pilot-links { display: flex; flex-wrap: wrap; gap: 4px 24px; }
.pilot-links a { padding-block: 12px; min-height: 44px; }
.help { margin-top: 28px; max-width: 80ch; }
.help strong { font-weight: 600; }
.help p { color: var(--muted); font-size: 14px; margin-top: 6px; }
footer { display: flex; justify-content: space-between; gap: 24px; padding-block: 24px 32px; color: var(--muted); font-size: 14px; }
footer a { min-height: 44px; padding-block: 10px; }
footer span { padding-block: 10px; }
@media (max-width: 800px) {
  .wrap { width: calc(100% - 40px); }
  .link-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .math-content { gap: 20px; }
  .start-panel, .math-area { padding: 22px; }
}
@media (max-width: 560px) {
  .wrap { width: calc(100% - 32px); }
  .masthead { min-height: 76px; gap: 12px; align-items: flex-start; padding-top: 20px; }
  .brand { gap: 8px; font-size: 15px; }
  .mark { font-size: 27px; }
  .sign-in { max-width: 110px; padding-top: 0; font-size: 13px; }
  .intro { padding: 16px 0 26px; }
  .intro p { font-size: 16px; margin-top: 18px; }
  .start-panel { grid-column: 1 / -1; padding: 22px; }
  .start-panel p { margin-block: 12px 16px; }
  .parent-area { margin-top: 28px; }
  .section-heading { display: block; }
  .section-heading p { margin-top: 8px; }
  .link-grid { grid-template-columns: 1fr; }
  .math-content { grid-template-columns: 1fr; gap: 8px; }
  .math-area { margin-top: 20px; padding: 22px; }
  .math-links { margin-top: 8px; }
  .text-action { align-items: baseline; }
  .pilot-links { flex-direction: column; align-items: flex-start; }
}