:root {
  --aqua: #00778b;
  --aqua-dark: #005a69;
  --aqua-tint: #e6f4f6;
  --gold: #ffc72c;
  --ink: #16212b;
  --muted: #4d5b66;
  --line: #d6dde2;
  --bg: #fbfaf6;
  --card: #ffffff;
  --ok: #1d6b3a;
  --error: #a3261b;
}

@media (prefers-color-scheme: dark) {
  :root {
    --aqua: #4fc3d4;
    --aqua-dark: #7fd6e2;
    --aqua-tint: #10292e;
    --ink: #eef2f4;
    --muted: #a9b6bf;
    --line: #2d3a43;
    --bg: #0f171c;
    --card: #16222a;
    --ok: #6fd192;
    --error: #ff8a7d;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  font-size: 17px;
  line-height: 1.55;
  color: var(--ink);
  background: var(--bg);
}

a { color: var(--aqua); }

.wrap { max-width: 1080px; margin: 0 auto; padding: 0 16px; }

.top { border-bottom: 4px solid var(--gold); background: var(--card); }
.top .wrap { padding-top: 16px; padding-bottom: 16px; }
.brand { font-weight: 800; font-size: 1.25rem; letter-spacing: 0.02em; color: var(--aqua); }
.brand span { font-weight: 500; color: var(--ink); }

.hero { background: var(--aqua-tint); padding: 48px 0; }
.hero-grid { display: grid; gap: 32px; grid-template-columns: 1.2fr 1fr; align-items: start; }
.eyebrow { margin: 0 0 8px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.08em; font-size: 0.8rem; color: var(--aqua-dark); }
h1 { font-size: clamp(1.9rem, 4vw, 2.8rem); line-height: 1.15; margin: 0 0 16px; }
.lede { font-size: 1.1rem; margin: 0 0 20px; }

.subjects { list-style: none; padding: 0; margin: 0; display: flex; flex-wrap: wrap; gap: 8px; }
.subjects li { background: var(--card); border: 1px solid var(--line); border-radius: 999px; padding: 4px 14px; font-size: 0.95rem; font-weight: 600; }

.card { background: var(--card); border: 1px solid var(--line); border-top: 6px solid var(--aqua); border-radius: 12px; padding: 24px; box-shadow: 0 6px 24px rgba(0, 0, 0, 0.06); }
.card h2 { margin: 0 0 4px; font-size: 1.4rem; }
.muted { color: var(--muted); margin: 0 0 16px; }

label { display: block; font-weight: 600; margin: 14px 0 6px; }
input[type="email"], input[type="text"], select {
  width: 100%;
  font: inherit;
  padding: 10px 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--bg);
  color: var(--ink);
}
input:focus, select:focus, button:focus-visible { outline: 3px solid var(--gold); outline-offset: 1px; }

fieldset { border: 0; padding: 0; margin: 14px 0 0; }
legend { font-weight: 600; padding: 0; margin-bottom: 6px; }
label.check { display: inline-flex; align-items: center; gap: 6px; font-weight: 500; margin: 0 18px 0 0; }
label.check input { width: 18px; height: 18px; }

.hp { position: absolute; left: -10000px; width: 1px; height: 1px; overflow: hidden; }

button {
  width: 100%;
  margin-top: 20px;
  font: inherit;
  font-weight: 700;
  padding: 12px;
  border: 0;
  border-radius: 8px;
  background: var(--aqua);
  color: #fff;
  cursor: pointer;
}
button:hover { background: var(--aqua-dark); }
button:disabled { opacity: 0.6; cursor: wait; }
@media (prefers-color-scheme: dark) { button { color: #0f171c; } }

.status { min-height: 1.4em; margin: 12px 0 0; font-weight: 600; }
.status.ok { color: var(--ok); }
.status.ok::before { content: "✓ "; }
.status.error { color: var(--error); }
.status.error::before { content: "! "; }
.fine { font-size: 0.85rem; color: var(--muted); margin: 8px 0 0; }

.points { padding: 48px 0; }
.points-grid { display: grid; gap: 24px; grid-template-columns: repeat(3, 1fr); }
.points h3 { margin: 0 0 8px; font-size: 1.1rem; border-left: 4px solid var(--gold); padding-left: 10px; }
.points p { margin: 0; color: var(--muted); }

.foot { border-top: 1px solid var(--line); padding: 24px 0 40px; font-size: 0.95rem; }
.foot p { margin: 0 0 6px; }

.page { padding: 40px 16px 56px; max-width: 720px; }
.page h1 { font-size: 2rem; }
.page h2 { font-size: 1.2rem; margin-top: 28px; }

@media (max-width: 820px) {
  .hero { padding: 32px 0; }
  .hero-grid, .points-grid { grid-template-columns: 1fr; }
}

.notice { padding: 0 0 40px; }
.notice p { margin: 0; padding: 16px 20px; background: var(--card); border: 1px solid var(--line); border-left: 4px solid var(--aqua); border-radius: 8px; }

/* Answer-key pages (/keys/...) */
.unlock { max-width: 480px; margin-top: 8px; }
.key h2 { font-size: 1.5rem; margin: 40px 0 8px; padding-top: 16px; border-top: 4px solid var(--gold); }
.key h2 span { color: var(--muted); font-weight: 600; }
.key h3 { font-size: 1.15rem; margin: 28px 0 6px; color: var(--aqua-dark); }
.key h4 { font-size: 1.05rem; margin: 24px 0 6px; }
.key p { margin: 6px 0; }
.key pre { background: var(--card); border: 1px solid var(--line); border-radius: 8px; padding: 10px 14px; overflow-x: auto; font-size: 1rem; line-height: 1.35; display: inline-block; min-width: 10em; margin: 6px 0; }
.key ul, .key ol { margin: 6px 0; padding-left: 24px; }
.key table { border-collapse: collapse; margin: 10px 0; display: block; overflow-x: auto; max-width: 100%; }
.key th, .key td { border: 1px solid var(--line); padding: 4px 10px; text-align: left; }
.key th { background: var(--aqua-tint); }
.contents { background: var(--card); border: 1px solid var(--line); border-radius: 12px; padding: 8px 20px 16px; margin: 24px 0; }
.contents h2 { border: 0; margin: 8px 0; padding: 0; font-size: 1.2rem; }
.contents-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px 24px; }
.contents h3 { margin: 8px 0 4px; font-size: 1rem; color: var(--ink); }
.contents ul { list-style: none; padding: 0; margin: 0; display: flex; flex-wrap: wrap; gap: 4px 12px; }
.rules { background: var(--aqua-tint); border-radius: 8px; padding: 12px 16px; margin: 16px 0; }
.rules summary { font-weight: 700; cursor: pointer; }
.rules li { margin: 6px 0; }
.top-link { font-size: 0.9rem; margin-top: 16px; }
.print { width: auto; margin: 4px 0 0; padding: 8px 16px; }
@media (max-width: 820px) { .contents-grid { grid-template-columns: 1fr; } }
@media print {
  .top, .foot, .print, .top-link, .contents { display: none; }
  body { background: #fff; color: #000; font-size: 12pt; }
  .key h2 { break-before: page; border-top: 0; }
  .key h3, .key h4 { break-after: avoid; }
}