:root {
  --ink: #1a1a17;
  --ink-soft: #565248;
  --paper: #faf7f0;
  --paper-panel: #f1ecdf;
  --rule: #d8d0bc;
  --accent: #8a6d1f;
  --accent-quiet: #cfc6a8;
  /* Môi trường Ví dụ (vd) của sách: GammaOchre / GammaOchreTint.
     Repository không chứa giá trị CMYK của preamble, nên hai màu này được lấy gần đúng từ
     màu nhấn của trang (#8a6d1f). Chữ trắng trên #8a6d1f đạt tỷ lệ tương phản khoảng 4.9:1. */
  --ochre: #8a6d1f;
  --ochre-tint: #f6f0df;
}
@media (prefers-color-scheme: dark) {
  :root {
    --ochre-tint: #211d10;
    --ink: #ece7da; --ink-soft: #b0aa97; --paper: #14130d;
    --paper-panel: #1c1a12; --rule: #34301f; --accent: #d4b04a; --accent-quiet: #47401f;
  }
}
* { box-sizing: border-box; }
html { scroll-padding-top: env(safe-area-inset-top, 0px); }
body {
  margin: 0; background: var(--paper); color: var(--ink);
  font-family: "Iowan Old Style", "Palatino Linotype", Georgia, "Noto Serif", serif;
  line-height: 1.7; -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}
.sans, .site-header, .site-footer, .meta, .btn, .kicker { font-family: "Helvetica Neue", Arial, sans-serif; }
.inner { max-width: 680px; margin: 0 auto; padding: 0 1.5rem; }
a { color: var(--accent); }
a:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 3px;
  border-radius: 2px;
}
img { display: block; max-width: 100%; height: auto; }
p { margin: 0 0 1.1rem; }

/* header */
.site-header { border-bottom: 1px solid var(--rule); padding: 1rem 0; }
.site-header .inner { display: flex; flex-wrap: wrap; align-items: baseline; justify-content: space-between; gap: 0.5rem 1.5rem; }
.brand { color: var(--ink); text-decoration: none; font-size: 1.05rem; font-weight: 600; letter-spacing: 0.02em; }
.site-header nav ul { list-style: none; margin: 0; padding: 0; display: flex; gap: 1.2rem; font-size: 0.9rem; }
.site-header nav a { color: var(--ink-soft); text-decoration: none; }
.site-header nav a:hover, .site-header nav a[aria-current="page"] { color: var(--ink); text-decoration: underline; text-underline-offset: 4px; }

/* blog index */
.blog-hero { padding: 3.5rem 0 2rem; }
.kicker { font-size: 0.78rem; letter-spacing: 0.1em; color: var(--accent); margin: 0 0 1rem; }
h1 { font-size: clamp(2.2rem, 7vw, 3.4rem); line-height: 1.05; margin: 0 0 1rem; font-weight: 600; letter-spacing: -0.01em; }
.lede { font-size: 1.12rem; color: var(--ink-soft); margin: 0 0 1.2rem; }
.back-link { font-family: "Helvetica Neue", Arial, sans-serif; font-size: 0.9rem; }

.post-list { padding: 1rem 0 4rem; }
.post-card { border-top: 1px solid var(--rule); padding-top: 2rem; }
.post-card figure { margin: 0 0 1.4rem; }
.post-card img, .post-figure img { width: 100%; border-radius: 4px; border: 1px solid var(--rule); background: var(--paper-panel); }
.post-card h2 { font-size: 1.55rem; line-height: 1.25; margin: 0 0 0.6rem; font-weight: 600; }
.post-card h2 a { color: var(--ink); text-decoration: none; }
.post-card h2 a:hover { text-decoration: underline; text-underline-offset: 4px; }
.meta { font-size: 0.85rem; color: var(--ink-soft); margin: 0 0 0.9rem; }
.btn {
  display: inline-block; padding: 0.75rem 1.4rem; border: 1px solid var(--ink); border-radius: 3px;
  color: var(--ink); text-decoration: none; font-size: 0.95rem;
  transition: background 0.15s ease, color 0.15s ease;
}
.btn:hover { background: var(--ink); color: var(--paper); }

/* article */
.post-head { padding: 3.5rem 0 1.5rem; }
.post-head h1 { font-size: clamp(1.9rem, 6vw, 2.9rem); line-height: 1.12; }
.post-figure { margin: 0 0 2.5rem; }
.post-figure figcaption { font-family: "Helvetica Neue", Arial, sans-serif; font-size: 0.8rem; color: var(--ink-soft); margin-top: 0.6rem; }
.post-subtitle { font-style: italic; color: var(--ink-soft); margin: 0; font-size: 1.05rem; }
.english-term { font-style: italic; }
.post-body h2 { font-size: 1.4rem; margin: 2.4rem 0 0.9rem; font-weight: 600; }
/* Chiều rộng cột chữ do .inner quyết định (632px nội dung), bằng ảnh hero và khung Ví dụ. */
.post-body ul { margin: 0 0 1.1rem; padding-left: 1.4rem; }
.post-body li { margin-bottom: 0.5rem; }
.references { margin-top: 2.5rem; }
.references h2 { font-size: 1.4rem; margin: 0 0 0.9rem; font-weight: 600; }
.references ol { padding-left: 1.4rem; margin: 0; }

/* công thức: display math cuộn ngang trong vùng công thức, không làm tràn trang */
.math-display { margin: 1.2rem 0; }
mjx-container[display="true"] { display: block; max-width: 100%; overflow-x: auto; overflow-y: hidden; margin: 1rem 0 !important; }

/* môi trường Ví dụ */
.gamma-example { border: 2px solid var(--ochre); border-radius: 6px; background: var(--ochre-tint); margin: 2.4rem 0; overflow: hidden; }
.gamma-example__header { background: var(--ochre); padding: 0.65rem 1.25rem; }
.gamma-example__title { margin: 0; color: #fff; font-style: italic; font-weight: 600; font-size: 1.05rem; line-height: 1.4; }
.gamma-example__body { padding: 0 1.25rem 1.2rem; }
.gamma-example__body section:first-child > h2 { margin-top: 1.4rem; }
.gamma-example__body p:last-child { margin-bottom: 0; }
@media (max-width: 480px) {
  .gamma-example__header { padding: 0.6rem 1rem; }
  .gamma-example__body { padding: 0 1rem 1rem; }
}

.note {
  background: var(--paper-panel); border: 1px solid var(--rule); border-radius: 10px;
  padding: 1.1rem 1.4rem; margin: 2.5rem 0 0;
  font-family: "Helvetica Neue", Arial, sans-serif; font-size: 0.88rem; color: var(--ink-soft);
}
.note p { margin: 0; }

/* lời mời hỏi đáp qua Messenger (cuối bài, trước hàng điều hướng) */
.ask { margin: 2.5rem 0 0; padding: 1.5rem 0 0; border-top: 1px solid var(--rule); }
.ask__text { margin: 0 0 1rem; font-size: 1.05rem; }
.ask__fallback { margin: 1rem 0 0; font-family: "Helvetica Neue", Arial, sans-serif; font-size: 0.875rem; color: var(--ink-soft); }
.ask .btn { min-height: 44px; }
@media (max-width: 480px) { .ask .btn { display: block; text-align: center; } }
.cta-row { display: flex; flex-wrap: wrap; gap: 0.9rem; margin: 2.5rem 0 4rem; }

/* footer */
.site-footer { padding: 2.5rem 0 3.5rem; border-top: 1px solid var(--rule); font-size: 0.78rem; color: var(--ink-soft); }
.site-footer .inner { display: flex; flex-direction: column; gap: 0.5rem; }
.site-footer a { color: var(--ink-soft); }

/* theo dõi Gamma: hàng icon thu gọn trong footer */
.follow-mini { display: flex; flex-wrap: wrap; align-items: center; gap: 0.25rem 1rem; margin-bottom: 0.75rem; }
.follow-mini__list { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: 0.5rem; }
.follow-mini__link {
  display: inline-flex; align-items: center; justify-content: center; width: 48px; height: 48px;
  border: 1px solid var(--rule); border-radius: 50%; color: var(--ink-soft);
  transition: transform 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}
.follow-mini__link svg { width: 26px; height: 26px; }
.follow-mini__link:hover { color: var(--accent); border-color: var(--accent); transform: translateY(-2px); }
@media (prefers-reduced-motion: reduce) { .follow-mini__link { transition: none; } .follow-mini__link:hover { transform: none; } }