:root {
  color-scheme: light;
  --page: #f5f7fb;
  --surface: #ffffff;
  --ink: #172033;
  --muted: #667085;
  --line: #dce2ec;
  --accent: #315fa7;
  --accent-soft: #edf3ff;
  --success: #246b52;
  --danger: #9b2c2c;
  font-family: -apple-system, BlinkMacSystemFont, "Hiragino Sans", "Yu Gothic", "Segoe UI", sans-serif;
  font-synthesis: none;
  line-height: 1.8;
}

* { box-sizing: border-box; }
html { background: var(--page); }
body { min-width: 0; margin: 0; color: var(--ink); background: var(--page); -webkit-font-smoothing: antialiased; }
a { color: inherit; text-underline-offset: .2em; }
a:focus-visible, button:focus-visible, input:focus-visible, summary:focus-visible { outline: 3px solid #8fb4ef; outline-offset: 3px; }
h1, h2, h3, p { overflow-wrap: anywhere; }
button, input { font: inherit; }

.visually-hidden { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0; }
.site-header { border-bottom: 1px solid var(--line); background: rgba(245,247,251,.94); }
.site-header__inner, .site-footer__inner, .site-main { width: min(1080px, calc(100% - 40px)); margin-inline: auto; }
.site-header__inner { min-height: 66px; display: flex; align-items: center; justify-content: space-between; gap: 24px; }
.site-brand { font-size: 1.18rem; font-weight: 800; letter-spacing: -.03em; text-decoration: none; }
.site-note { color: var(--muted); font-size: .78rem; }
.site-main { min-height: 72vh; }
.site-footer { margin-top: 88px; border-top: 1px solid var(--line); }
.site-footer__inner { min-height: 96px; display: flex; align-items: center; justify-content: space-between; gap: 24px; color: var(--muted); font-size: .76rem; }

.back-link { display: inline-flex; gap: .35em; align-items: center; margin-top: 24px; color: var(--muted); font-size: .82rem; text-decoration: none; }
.back-link:hover { color: var(--ink); }
.eyebrow { margin: 0 0 10px; color: var(--accent); font-size: .76rem; font-weight: 700; letter-spacing: .06em; }
.lead { color: var(--muted); font-size: 1rem; line-height: 1.9; }

.home-hero { padding: 68px 0 52px; }
.home-hero h1 { max-width: 760px; margin: 0; font-size: clamp(2.25rem, 6vw, 4.4rem); line-height: 1.08; letter-spacing: -.055em; font-weight: 720; }
.home-hero .lead { max-width: 650px; margin: 26px 0 0; font-size: clamp(1rem, 2vw, 1.15rem); }
.section-heading { display: flex; justify-content: space-between; align-items: baseline; gap: 24px; margin: 0 0 18px; padding-top: 26px; border-top: 1px solid var(--line); }
.section-heading h2 { margin: 0; font-size: 1rem; letter-spacing: .02em; }
.section-heading span { color: var(--muted); font-size: .74rem; }
.resource-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 14px; margin: 0 0 48px; }
.resource-card { display: block; min-height: 150px; padding: 24px; border: 1px solid var(--line); border-radius: 16px; background: var(--surface); text-decoration: none; transition: transform .15s ease, border-color .15s ease, box-shadow .15s ease; }
.resource-card:hover { transform: translateY(-2px); border-color: #b8c6db; box-shadow: 0 12px 28px rgba(42,61,89,.08); }
.resource-card__meta { display: block; margin-bottom: 10px; color: var(--muted); font-size: .75rem; }
.resource-card__title { display: block; font-size: 1.18rem; line-height: 1.45; font-weight: 700; }
.resource-card__arrow { display: block; margin-top: 20px; color: var(--accent); font-size: .78rem; font-weight: 700; }

.page-hero { max-width: 820px; padding: 54px 0 42px; }
.page-hero h1 { margin: 0; font-size: clamp(2rem, 5vw, 3.5rem); line-height: 1.16; letter-spacing: -.045em; font-weight: 720; }
.page-hero .lead { max-width: 700px; margin: 22px 0 0; }

.topic-section { margin-top: 12px; padding-top: 30px; border-top: 1px solid var(--line); }
.topic-section + .topic-section { margin-top: 40px; }
.topic-section h2 { margin: 0 0 18px; font-size: 1.15rem; }
.link-list { display: grid; gap: 10px; margin: 0; padding: 0; list-style: none; }
.link-list a { display: flex; justify-content: space-between; gap: 24px; padding: 18px 0; border-bottom: 1px solid var(--line); text-decoration: none; font-weight: 650; }
.link-list a::after { content: "→"; color: var(--accent); }
.link-list a:hover { color: var(--accent); }

.reading-shell { width: min(760px, 100%); margin-inline: auto; padding-top: 20px; }
.article-hero { padding: 38px 0 38px; border-bottom: 1px solid var(--line); }
.article-hero h1 { margin: 0; font-size: clamp(2rem, 5vw, 3.4rem); line-height: 1.18; letter-spacing: -.04em; font-weight: 720; }
.article-hero .lead { margin: 22px 0 0; }
.article-body { padding: 44px 0 12px; }
.explanation-point { scroll-margin-top: 24px; padding: 0 0 30px; }
.explanation-point + .explanation-point { padding-top: 30px; border-top: 1px solid var(--line); }
.explanation-point__text { margin: 0; font-size: clamp(1.02rem, 2vw, 1.12rem); line-height: 2; }
.source-link { display: inline-flex; align-items: baseline; margin-left: .55em; color: var(--accent); font-size: .72rem; font-weight: 650; text-decoration: none; white-space: nowrap; }
.source-link:hover { text-decoration: underline; }

.quiz-shell { width: min(780px, 100%); margin-inline: auto; padding-top: 20px; }
.quiz-card { margin-top: 12px; padding: 28px; border: 1px solid var(--line); border-radius: 18px; background: var(--surface); }
.quiz-prompt { margin: 0 0 24px; font-size: clamp(1.08rem, 2.2vw, 1.24rem); line-height: 1.8; font-weight: 700; }
.choice-fieldset { margin: 0; padding: 0; border: 0; }
.choice-list { display: grid; gap: 10px; margin: 0; padding: 0; list-style: none; counter-reset: choices; }
.choice-list li { counter-increment: choices; position: relative; }
.choice-option { display: grid; grid-template-columns: auto 30px minmax(0, 1fr); gap: 10px; align-items: start; padding: 15px 16px; border: 1px solid var(--line); border-radius: 12px; background: #fbfcfe; cursor: pointer; transition: border-color .15s ease, background .15s ease, box-shadow .15s ease; }
.choice-option::before { content: counter(choices); display: grid; place-items: center; width: 26px; height: 26px; border-radius: 50%; background: var(--accent-soft); color: var(--accent); font-size: .78rem; font-weight: 800; }
.choice-option input { margin-top: .42rem; accent-color: var(--accent); }
.choice-option:has(input:checked) { border-color: #8eacd8; background: #f5f8ff; box-shadow: 0 0 0 2px rgba(49,95,167,.08); }
.quiz-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 12px 18px; margin-top: 22px; }
.answer-button { min-height: 44px; padding: 10px 20px; border: 0; border-radius: 999px; background: var(--ink); color: #fff; cursor: pointer; font-weight: 750; }
.answer-button:hover { background: #26334c; }
.quiz-hint { margin: 0; color: var(--muted); font-size: .78rem; }
.answer-result { margin-top: 24px; padding-top: 20px; border-top: 1px solid var(--line); }
.answer-result[hidden] { display: none; }
.answer-judgement { margin: 0 0 10px; font-weight: 800; }
.answer-judgement.is-correct { color: var(--success); }
.answer-judgement.is-incorrect { color: var(--danger); }
.answer-box { margin-top: 18px; border-top: 1px solid var(--line); }
.answer-box summary { cursor: pointer; padding: 18px 0; color: var(--accent); font-weight: 750; list-style-position: inside; }
.answer-content { padding: 0 0 6px; }
.answer-correct { color: var(--success); font-weight: 750; }
.explanation-link { display: inline-flex; margin-top: 4px; color: var(--accent); font-weight: 700; }

.question-navigation { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; margin-top: 28px; }
.question-navigation__item { display: flex; min-height: 96px; flex-direction: column; justify-content: center; gap: 4px; padding: 18px 20px; border: 1px solid var(--line); border-radius: 14px; background: var(--surface); text-decoration: none; }
.question-navigation__item:hover { border-color: #b8c6db; box-shadow: 0 10px 24px rgba(42,61,89,.06); }
.question-navigation__item span { color: var(--muted); font-size: .74rem; }
.question-navigation__item strong { line-height: 1.5; }
.question-navigation__item--next { text-align: right; }

.muted { color: var(--muted); }

@media (max-width: 720px) {
  .site-header__inner, .site-footer__inner, .site-main { width: min(100% - 28px, 1080px); }
  .site-header__inner { min-height: 58px; }
  .site-note { display: none; }
  .site-footer { margin-top: 64px; }
  .site-footer__inner { min-height: 84px; display: block; padding: 22px 0; }
  .site-footer__inner span { display: block; margin-bottom: 4px; }
  .home-hero { padding: 48px 0 38px; }
  .resource-grid { grid-template-columns: 1fr; }
  .resource-card { min-height: 0; padding: 20px; }
  .page-hero { padding: 40px 0 32px; }
  .article-hero { padding: 32px 0; }
  .article-body { padding-top: 34px; }
  .quiz-card { padding: 20px 16px; border-radius: 14px; }
  .choice-option { grid-template-columns: auto 28px minmax(0, 1fr); padding: 13px; }
  .quiz-actions { align-items: stretch; }
  .answer-button { width: 100%; }
  .question-navigation { grid-template-columns: 1fr; }
  .question-navigation > span:empty { display: none; }
  .question-navigation__item, .question-navigation__item--next { min-height: 0; text-align: left; }
}