/* Hypothesis Testing Guide — design system.
   Paper + pine editorial look; every color flows through the tokens below,
   and the dark theme only overrides tokens (plus a few SVG accents). */

:root {
  color-scheme: light dark;

  /* surfaces */
  --paper: #faf9f5;
  --paper-deep: #f2f0e9;
  --panel: #ffffff;
  --panel-soft: #f6f5ef;
  --panel-inset: #efeee6;

  /* ink */
  --ink: #1e2a25;
  --ink-strong: #101b16;
  --muted: #5b6a63;
  --faint: #8b978f;

  /* accent */
  --pine: #17685a;
  --pine-strong: #0e4c41;
  --pine-soft: #e0efe9;
  --pine-faint: #eef6f1;
  --on-pine: #ffffff;

  /* secondary hues */
  --sky: #33607e;
  --sky-soft: #e5eef4;
  --amber: #8f5d14;
  --amber-soft: #f8eed7;
  --rust: #a43e35;
  --rust-soft: #f8e8e4;

  /* lines */
  --line: #e4e1d6;
  --line-strong: #c6c2b2;
  --focus: #146e9e;

  /* header / footer glass */
  --header-bg: rgb(250 249 245 / 92%);
  --header-line: rgb(198 194 178 / 55%);
  --footer-bg: rgb(242 240 233 / 80%);
  --backdrop: rgb(16 27 22 / 42%);

  --code-bg: #10231e;
  --code-ink: #d6e6df;
  --code-line: #24423a;
  --code-muted: #8fb0a5;

  --shadow-1: 0 1px 2px rgb(16 27 22 / 6%);
  --shadow-2: 0 10px 30px rgb(16 27 22 / 10%);

  --r-sm: 0.4rem;
  --r-md: 0.65rem;
  --r-lg: 1rem;

  --content: 78rem;
  --header-h: 4.25rem;

  --sans: "Inter", ui-sans-serif, system-ui, -apple-system, "Segoe UI", "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  --mono: ui-monospace, "SF Mono", "SFMono-Regular", Menlo, Consolas, "Liberation Mono", monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --paper: #141b18;
    --paper-deep: #0f1512;
    --panel: #1b2420;
    --panel-soft: #171f1b;
    --panel-inset: #202b26;

    --ink: #cdddd5;
    --ink-strong: #edf6f1;
    --muted: #93a59c;
    --faint: #6f8078;

    --pine: #55b898;
    --pine-strong: #7fcdb2;
    --pine-soft: #21453a;
    --pine-faint: #1a332b;
    --on-pine: #0b1f19;

    --sky: #74aecf;
    --sky-soft: #1c333f;
    --amber: #d9ab5e;
    --amber-soft: #3a3116;
    --rust: #dd8b80;
    --rust-soft: #44201b;

    --line: #2b3a33;
    --line-strong: #45584f;
    --focus: #5cb8e0;

    --header-bg: rgb(17 24 20 / 90%);
    --header-line: rgb(69 88 79 / 60%);
    --footer-bg: rgb(15 21 18 / 80%);
    --backdrop: rgb(4 8 6 / 62%);

    --code-bg: #0e1c17;
    --code-ink: #cfe3da;
    --code-line: #22382f;
    --code-muted: #7fa093;

    --shadow-1: 0 1px 2px rgb(0 0 0 / 40%);
    --shadow-2: 0 12px 34px rgb(0 0 0 / 50%);
  }
}

/* ---------- base ---------- */

*,
*::before,
*::after { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-h) + 1.25rem);
  background: var(--paper);
  text-size-adjust: 100%;
  -webkit-text-size-adjust: 100%;
}

body {
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  margin: 0;
  color: var(--ink);
  font-family: var(--sans);
  font-size: 1rem;
  line-height: 1.7;
  font-feature-settings: "tnum";
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4 {
  margin: 0 0 0.6rem;
  color: var(--ink-strong);
  line-height: 1.25;
  text-wrap: balance;
}

h1 { font-size: clamp(1.7rem, 3.4vw, 2.5rem); letter-spacing: -0.015em; }
h2 { font-size: clamp(1.22rem, 2.2vw, 1.55rem); letter-spacing: -0.01em; }
h3 { font-size: 1.02rem; }

p { margin: 0 0 0.9rem; }
p:last-child { margin-bottom: 0; }

a { color: var(--pine); text-decoration: underline; text-decoration-color: color-mix(in srgb, var(--pine) 40%, transparent); text-underline-offset: 0.18em; }
a:hover { text-decoration-color: currentColor; }

code, kbd { font-family: var(--mono); }

::selection { color: var(--ink-strong); background: var(--pine-soft); }

:focus-visible { outline: 2px solid var(--focus); outline-offset: 2px; border-radius: 2px; }

[hidden] { display: none !important; }

.sr-only {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

/* ---------- shared atoms ---------- */

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  margin: 0 0 0.8rem;
  color: var(--pine);
  font-family: var(--mono);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

.eyebrow::before { width: 1.6rem; height: 1px; content: ""; background: currentColor; }

.lead {
  max-width: 62ch;
  color: var(--muted);
  font-size: clamp(1rem, 1.6vw, 1.12rem);
  line-height: 1.75;
  text-wrap: pretty;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.4rem;
  min-height: 2.5rem;
  padding: 0.45rem 0.95rem;
  border: 1px solid var(--line-strong);
  border-radius: var(--r-sm);
  color: var(--ink);
  background: var(--panel);
  font: inherit;
  font-weight: 600;
  line-height: 1.2;
  text-decoration: none;
  cursor: pointer;
  transition: border-color 130ms ease, background 130ms ease, color 130ms ease;
}

.button:hover { border-color: var(--pine); color: var(--pine-strong); background: var(--pine-faint); }

.button.primary { border-color: var(--pine); color: var(--on-pine); background: var(--pine); }
.button.primary:hover { border-color: var(--pine-strong); background: var(--pine-strong); color: var(--on-pine); }
.button.secondary { border-color: var(--line-strong); color: var(--sky); background: var(--sky-soft); }
.button.ghost { border-color: transparent; background: transparent; color: var(--muted); }
.button.ghost:hover { color: var(--pine-strong); background: var(--pine-faint); }
.button.tiny { min-height: 1.9rem; padding: 0.2rem 0.65rem; font-size: 0.8rem; }
.button:disabled { opacity: 0.55; cursor: default; }

.chip {
  display: inline-flex;
  align-items: center;
  padding: 0.12rem 0.62rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--muted);
  background: var(--panel-soft);
  font-family: var(--mono);
  font-size: 0.74rem;
  letter-spacing: 0.02em;
}

.hint { color: var(--faint); font-size: 0.86rem; }

.empty-state {
  padding: 2.2rem 1.4rem;
  border: 1px dashed var(--line-strong);
  border-radius: var(--r-md);
  color: var(--muted);
  text-align: center;
}

/* ---------- header ---------- */

.skip-link {
  position: fixed;
  z-index: 200;
  top: 0.7rem;
  left: 0.7rem;
  padding: 0.6rem 0.9rem;
  border-radius: var(--r-sm);
  color: var(--paper);
  background: var(--ink-strong);
  box-shadow: var(--shadow-2);
  font-weight: 700;
  text-decoration: none;
  transform: translateY(-220%);
  transition: transform 150ms ease;
}

.skip-link:focus { transform: translateY(0); }

.site-header {
  position: sticky;
  z-index: 60;
  top: 0;
  border-bottom: 1px solid var(--header-line);
  background: var(--header-bg);
  backdrop-filter: blur(14px) saturate(130%);
}

.header-inner {
  display: flex;
  align-items: center;
  gap: 1.1rem;
  width: min(calc(100% - 2.4rem), var(--content));
  min-height: var(--header-h);
  margin-inline: auto;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.65rem;
  margin-right: auto;
  color: inherit;
  text-decoration: none;
}

.brand-mark {
  display: grid;
  place-items: center;
  width: 2.15rem;
  height: 2.15rem;
  border: 1px solid var(--pine);
  border-radius: var(--r-sm);
  color: var(--pine);
  background: var(--pine-faint);
  font-family: var(--mono);
  font-size: 1.05rem;
  font-weight: 700;
}

.brand-copy { display: grid; line-height: 1.25; }
.brand-copy strong { color: var(--ink-strong); font-size: 0.98rem; letter-spacing: -0.01em; }
.brand-copy span { color: var(--faint); font-size: 0.74rem; }

.site-nav { display: flex; gap: 0.2rem; }

.site-nav a {
  padding: 0.42rem 0.75rem;
  border-radius: var(--r-sm);
  color: var(--muted);
  font-size: 0.92rem;
  font-weight: 600;
  text-decoration: none;
}

.site-nav a:hover { color: var(--pine-strong); background: var(--pine-faint); }
.site-nav a[aria-current="page"] { color: var(--pine-strong); background: var(--pine-soft); }

.header-actions { display: flex; align-items: center; gap: 0.5rem; }

.palette-button {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  min-height: 2.3rem;
  padding: 0.3rem 0.7rem;
  border: 1px solid var(--line-strong);
  border-radius: var(--r-sm);
  color: var(--muted);
  background: var(--panel);
  font: inherit;
  font-size: 0.88rem;
  cursor: pointer;
}

.palette-button:hover { border-color: var(--pine); color: var(--pine-strong); }
.palette-button-glyph { font-size: 1rem; line-height: 1; }

.palette-button kbd {
  padding: 0.05rem 0.4rem;
  border: 1px solid var(--line);
  border-radius: 0.3rem;
  background: var(--panel-soft);
  font-size: 0.72rem;
  color: var(--faint);
}

.lang-toggle {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  min-height: 2.3rem;
  padding: 0.3rem 0.7rem;
  border: 1px solid var(--line-strong);
  border-radius: var(--r-sm);
  color: var(--ink);
  background: var(--panel);
  font: inherit;
  font-size: 0.85rem;
  cursor: pointer;
}

.lang-toggle:hover { border-color: var(--pine); color: var(--pine-strong); }
.lang-current { font-family: var(--mono); font-weight: 700; color: var(--pine); }

/* ---------- page frame ---------- */

.page-shell {
  flex: 1 0 auto;
  width: min(calc(100% - 2.4rem), var(--content));
  margin-inline: auto;
  padding: clamp(1.4rem, 3.4vw, 2.6rem) 0 3.4rem;
}

.app-mount[aria-busy="true"] { min-height: 40vh; }

.loading-state {
  display: grid;
  place-items: center;
  gap: 0.6rem;
  padding: 4rem 1rem;
  color: var(--faint);
}

.loading-mark {
  display: grid;
  place-items: center;
  width: 2.6rem;
  height: 2.6rem;
  border: 1px solid var(--line-strong);
  border-radius: var(--r-sm);
  color: var(--pine);
  font-family: var(--mono);
  font-size: 1.3rem;
}

.noscript-note {
  padding: 1.6rem;
  border: 1px solid var(--amber);
  border-radius: var(--r-md);
  background: var(--amber-soft);
}

.site-footer {
  flex: 0 0 auto;
  border-top: 1px solid var(--line);
  color: var(--muted);
  background: var(--footer-bg);
}

.footer-inner {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.4rem 1.6rem;
  width: min(calc(100% - 2.4rem), var(--content));
  margin-inline: auto;
  padding: 1.1rem 0;
  font-size: 0.88rem;
}

.footer-inner p { margin: 0; }
.footer-updated { color: var(--faint); font-family: var(--mono); font-size: 0.78rem; }
.footer-inner a { margin-left: auto; }

/* ---------- command palette ---------- */

.palette-backdrop {
  position: fixed;
  inset: 0;
  z-index: 90;
  background: var(--backdrop);
  backdrop-filter: blur(2px);
}

.palette {
  position: fixed;
  z-index: 100;
  top: min(12vh, 7rem);
  left: 50%;
  transform: translateX(-50%);
  width: min(calc(100% - 2rem), 40rem);
  overflow: hidden;
  border: 1px solid var(--line-strong);
  border-radius: var(--r-lg);
  background: var(--panel);
  box-shadow: var(--shadow-2);
}

body.palette-open { overflow: hidden; }

.palette-input-row {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  padding: 0.9rem 1rem;
  border-bottom: 1px solid var(--line);
}

.palette-glyph { color: var(--faint); font-size: 1.15rem; }

#palette-input {
  flex: 1;
  min-width: 0;
  border: 0;
  outline: 0;
  color: var(--ink-strong);
  background: transparent;
  font: inherit;
  font-size: 1.05rem;
}

#palette-input::placeholder { color: var(--faint); }

.palette-esc {
  padding: 0.15rem 0.5rem;
  border: 1px solid var(--line);
  border-radius: 0.3rem;
  color: var(--faint);
  background: var(--panel-soft);
  font-family: var(--mono);
  font-size: 0.72rem;
  cursor: pointer;
}

#palette-list {
  max-height: min(52vh, 24rem);
  padding: 0.45rem;
  margin: 0;
  overflow-y: auto;
  list-style: none;
  overscroll-behavior: contain;
  scrollbar-width: thin;
}

.palette-group {
  padding: 0.65rem 0.7rem 0.25rem;
  color: var(--faint);
  font-family: var(--mono);
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

#palette-list [role="option"] a {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.55rem 0.7rem;
  border-radius: var(--r-sm);
  color: var(--ink);
  text-decoration: none;
}

#palette-list [role="option"][aria-selected="true"] a {
  color: var(--pine-strong);
  background: var(--pine-soft);
}

.palette-item-title { font-weight: 600; }
.palette-item-meta { flex-shrink: 0; color: var(--faint); font-size: 0.78rem; }

.palette-empty { padding: 1.6rem 1rem; color: var(--muted); text-align: center; }

.palette-hint {
  padding: 0.55rem 1rem;
  margin: 0;
  border-top: 1px solid var(--line);
  color: var(--faint);
  background: var(--panel-soft);
  font-family: var(--mono);
  font-size: 0.72rem;
}

/* ---------- explorer ---------- */

.explore-hero { margin-bottom: clamp(1.4rem, 3vw, 2.2rem); }
.explore-hero h1 { max-width: 24ch; }

.explorer-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 21.5rem;
  gap: 1.4rem;
  align-items: start;
  margin-top: 1.4rem;
}

.facet-panel {
  padding: 1.05rem 1.15rem 0.9rem;
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  background: var(--panel);
  box-shadow: var(--shadow-1);
}

.facet-groups {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(13rem, 1fr));
  gap: 0.85rem 1.4rem;
}

.facet-group { min-width: 0; padding: 0; margin: 0; border: 0; }

.facet-group legend {
  padding: 0;
  margin-bottom: 0.4rem;
  color: var(--faint);
  font-family: var(--mono);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

.facet-options { display: flex; flex-wrap: wrap; gap: 0.35rem; }

.facet-chip {
  padding: 0.3rem 0.75rem;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  color: var(--ink);
  background: var(--panel);
  font: inherit;
  font-size: 0.86rem;
  font-weight: 550;
  line-height: 1.3;
  cursor: pointer;
  transition: border-color 120ms ease, background 120ms ease, color 120ms ease;
}

.facet-chip:hover { border-color: var(--pine); color: var(--pine-strong); }

.facet-chip[aria-pressed="true"] {
  border-color: var(--pine);
  color: var(--on-pine);
  background: var(--pine);
}

.facet-actions {
  display: flex;
  gap: 0.6rem;
  align-items: center;
  margin-top: 1rem;
  padding-top: 0.9rem;
  border-top: 1px dashed var(--line);
}

.inline-search { flex: 1; min-width: 0; }

.inline-search input {
  width: 100%;
  min-height: 2.55rem;
  padding: 0.45rem 0.9rem;
  border: 1px solid var(--line-strong);
  border-radius: var(--r-sm);
  outline: 0;
  color: var(--ink-strong);
  background: var(--panel-soft);
  font: inherit;
}

.inline-search input:focus { border-color: var(--focus); box-shadow: 0 0 0 3px color-mix(in srgb, var(--focus) 18%, transparent); }

.facet-hint { margin: 0.55rem 0 0; color: var(--faint); font-size: 0.78rem; }

.explorer-count-row {
  display: flex;
  align-items: baseline;
  gap: 0.8rem;
  margin: 0 0 0.75rem;
}

.section-label {
  margin: 0;
  font-size: 0.95rem;
  color: var(--ink-strong);
  letter-spacing: 0.01em;
}

.explorer-count { color: var(--faint); font-family: var(--mono); font-size: 0.8rem; }

.method-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(15.5rem, 1fr));
  gap: 0.7rem;
}

.method-grid.compact { grid-template-columns: repeat(auto-fill, minmax(13rem, 1fr)); }

.method-card {
  display: grid;
  gap: 0.35rem;
  align-content: start;
  min-height: 100%;
  padding: 0.85rem 0.95rem;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  color: inherit;
  background: var(--panel);
  text-decoration: none;
  transition: border-color 130ms ease, transform 130ms ease, box-shadow 130ms ease, opacity 130ms ease;
}

.method-card:hover {
  border-color: var(--pine);
  transform: translateY(-1px);
  box-shadow: var(--shadow-1);
}

.method-card-top { display: flex; flex-wrap: wrap; gap: 0.35rem; align-items: center; }

.method-card-title { color: var(--ink-strong); font-weight: 650; line-height: 1.35; }

.method-card-short {
  display: -webkit-box;
  -webkit-box-orient: vertical;
  -webkit-line-clamp: 2;
  overflow: hidden;
  color: var(--muted);
  font-size: 0.83rem;
  line-height: 1.55;
}

.method-card-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 0.3rem 0.7rem;
  align-items: baseline;
  margin-top: 0.1rem;
  color: var(--faint);
  font-family: var(--mono);
  font-size: 0.72rem;
}

.method-card-meta em { font-style: normal; color: var(--amber); }

.method-card-tag {
  padding: 0.05rem 0.5rem;
  border-radius: 999px;
  color: var(--on-pine);
  background: var(--pine);
  font-family: var(--mono);
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.05em;
}

.method-card.is-recommended { border-color: var(--pine); box-shadow: inset 3px 0 0 var(--pine); }
.method-card.is-dim { opacity: 0.55; }
.method-card.is-dim:hover { opacity: 0.9; }

.explorer-concepts { margin-top: 1.7rem; }
.explorer-concepts h2 { margin-bottom: 0.75rem; font-size: 0.95rem; }

/* guidance rail */

.guidance-rail {
  position: sticky;
  top: calc(var(--header-h) + 1.1rem);
  max-height: calc(100dvh - var(--header-h) - 2.4rem);
  padding: 1rem 1.05rem;
  overflow-y: auto;
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  background: var(--panel-soft);
  scrollbar-width: thin;
}

.guidance-rail > h2 {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-bottom: 0.8rem;
  font-size: 0.82rem;
  font-family: var(--mono);
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--pine);
}

.guidance-rail > h2::after { flex: 1; height: 1px; content: ""; background: var(--line); }

.guidance-empty { color: var(--faint); font-size: 0.88rem; line-height: 1.65; }

.guidance-rule + .guidance-rule { margin-top: 1.2rem; padding-top: 1.1rem; border-top: 1px dashed var(--line); }
.guidance-rule h3 { margin-bottom: 0.45rem; font-size: 0.95rem; }
.guidance-intro { color: var(--muted); font-size: 0.83rem; line-height: 1.6; }

.guidance-options {
  display: grid;
  gap: 0.5rem;
  padding: 0;
  margin: 0.7rem 0 0;
  list-style: none;
}

.guidance-option {
  display: grid;
  gap: 0.25rem;
  padding: 0.65rem 0.75rem;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  background: var(--panel);
  color: inherit;
  font-size: 0.83rem;
  line-height: 1.55;
  text-decoration: none;
  transition: border-color 130ms ease, box-shadow 130ms ease;
}

a.guidance-option:hover { border-color: var(--pine); box-shadow: var(--shadow-1); }
.guidance-option strong { color: var(--ink-strong); font-size: 0.86rem; }
.guidance-option span { color: var(--muted); }

.guidance-method {
  margin-top: 0.15rem;
  color: var(--pine-strong);
  font-weight: 650;
  font-size: 0.84rem;
}

.guidance-option.is-note { border-style: dashed; background: var(--amber-soft); border-color: color-mix(in srgb, var(--amber) 45%, transparent); }
.guidance-note { display: block; margin-top: 0.2rem; color: var(--amber); font-weight: 600; font-size: 0.8rem; }

/* ---------- method page ---------- */

.method-layout {
  display: grid;
  grid-template-columns: 15rem minmax(0, 1fr);
  gap: 2rem;
  align-items: start;
}

.method-toc {
  position: sticky;
  top: calc(var(--header-h) + 1.1rem);
  max-height: calc(100dvh - var(--header-h) - 2.4rem);
  overflow-y: auto;
  padding: 0.9rem 0.4rem 0.9rem 0;
  scrollbar-width: thin;
}

.toc-label {
  margin: 0 0 0.5rem 0.75rem;
  color: var(--faint);
  font-family: var(--mono);
  font-size: 0.7rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

.method-toc nav { display: grid; }

.method-toc a {
  display: flex;
  gap: 0.55rem;
  align-items: baseline;
  padding: 0.34rem 0.75rem;
  border-left: 2px solid transparent;
  color: var(--muted);
  font-size: 0.86rem;
  text-decoration: none;
}

.method-toc a i {
  font-family: var(--mono);
  font-style: normal;
  font-size: 0.7rem;
  color: var(--faint);
}

.method-toc a:hover { color: var(--pine-strong); }

.method-toc a[data-active] {
  border-left-color: var(--pine);
  color: var(--pine-strong);
  font-weight: 650;
  background: linear-gradient(to right, var(--pine-faint), transparent 85%);
}

.method-article { min-width: 0; }

.breadcrumbs {
  display: flex;
  gap: 0.55rem;
  margin-bottom: 0.9rem;
  color: var(--faint);
  font-size: 0.84rem;
}

.method-header { margin-bottom: 1.9rem; }
.method-header .lead { margin-top: 0.4rem; }

.chip-row { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-top: 0.9rem; }

.content-section { margin-bottom: 2.1rem; }

.content-section > h2 {
  display: flex;
  align-items: baseline;
  gap: 0.6rem;
  padding-bottom: 0.45rem;
  margin-bottom: 0.9rem;
  border-bottom: 1px solid var(--line);
}

.content-section > h2 i {
  font-family: var(--mono);
  font-style: normal;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--pine);
}

.content-section p, .content-section li { max-width: 76ch; }

.two-col {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(17rem, 1fr));
  gap: 0.75rem;
}

.info-card {
  padding: 0.9rem 1rem;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  background: var(--panel);
}

.info-card h3 {
  margin-bottom: 0.35rem;
  font-family: var(--mono);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.info-card.is-use { border-left: 3px solid var(--pine); }
.info-card.is-use h3 { color: var(--pine); }
.info-card.is-avoid { border-left: 3px solid var(--rust); }
.info-card.is-avoid h3 { color: var(--rust); }
.info-card p { font-size: 0.92rem; }

.hypothesis {
  padding: 0.9rem 1rem;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  background: var(--panel-soft);
}

.hypothesis h3 { margin-bottom: 0.3rem; font-size: 0.88rem; }
.hypothesis.h0 { border-left: 3px solid var(--sky); }
.hypothesis.h0 h3 { color: var(--sky); }
.hypothesis.h1 { border-left: 3px solid var(--pine); }
.hypothesis.h1 h3 { color: var(--pine); }
.hypothesis p { font-size: 0.94rem; }

.check-list {
  display: grid;
  gap: 0.45rem;
  padding: 0;
  margin: 0 0 0.4rem;
  list-style: none;
}

.check-list li {
  position: relative;
  padding-left: 1.6rem;
  font-size: 0.95rem;
}

.check-list li::before {
  position: absolute;
  top: 0.06em;
  left: 0;
  color: var(--pine);
  content: "→";
  font-family: var(--mono);
  font-weight: 700;
}

.symbol-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(16rem, 1fr));
  gap: 0.45rem;
  margin-bottom: 0.9rem;
}

.symbol-grid > div {
  display: flex;
  gap: 0.7rem;
  align-items: center;
  padding: 0.45rem 0.65rem;
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  background: var(--panel);
  font-size: 0.85rem;
}

.symbol-grid code {
  flex-shrink: 0;
  min-width: 3.4rem;
  padding: 0.15rem 0.45rem;
  border-radius: var(--r-sm);
  color: var(--ink-strong);
  background: var(--panel-inset);
  text-align: center;
  font-size: 0.88rem;
}

.symbol-grid span { color: var(--muted); }

.formula-list { display: grid; gap: 0.65rem; }

.formula-card {
  max-width: 100%;
  padding: 0.8rem 1rem;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  background: var(--panel);
}

.formula-card h3 {
  margin-bottom: 0.3rem;
  color: var(--faint);
  font-family: var(--mono);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}

.formula {
  max-width: 100%;
  overflow-x: auto;
  color: var(--ink-strong);
  text-align: center;
  scrollbar-width: thin;
}

.formula .katex-display { margin: 0.5rem 0; }
.formula-fallback { font-family: var(--mono); font-size: 0.85rem; color: var(--muted); }

.table-wrap {
  max-width: 100%;
  margin-bottom: 1rem;
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  background: var(--panel);
  scrollbar-width: thin;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-variant-numeric: tabular-nums;
  font-size: 0.92rem;
}

caption {
  padding: 0.6rem 0.85rem;
  border-bottom: 1px solid var(--line);
  color: var(--faint);
  font-family: var(--mono);
  font-size: 0.75rem;
  text-align: left;
}

th, td { padding: 0.5rem 0.85rem; text-align: left; }
thead th { border-bottom: 1px solid var(--line-strong); color: var(--muted); font-size: 0.8rem; font-weight: 650; }
tbody tr + tr td { border-top: 1px solid var(--line); }
tbody tr:nth-child(even) { background: var(--panel-soft); }

.calculation-steps {
  display: grid;
  gap: 0.55rem;
  padding: 0;
  margin: 1rem 0;
  list-style: none;
  counter-reset: step;
}

.calculation-steps li {
  position: relative;
  padding: 0.7rem 0.9rem 0.7rem 2.9rem;
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  background: var(--panel);
  font-size: 0.94rem;
  counter-increment: step;
}

.calculation-steps li::before {
  position: absolute;
  top: 0.72rem;
  left: 0.8rem;
  display: grid;
  place-items: center;
  width: 1.45rem;
  height: 1.45rem;
  border-radius: 50%;
  color: var(--on-pine);
  background: var(--pine);
  content: counter(step);
  font-family: var(--mono);
  font-size: 0.72rem;
  font-weight: 700;
}

.result-callout {
  padding: 0.9rem 1rem;
  border: 1px solid color-mix(in srgb, var(--pine) 35%, transparent);
  border-left: 3px solid var(--pine);
  border-radius: var(--r-md);
  background: var(--pine-faint);
}

.result-callout strong { color: var(--pine-strong); font-family: var(--mono); font-size: 0.78rem; letter-spacing: 0.1em; text-transform: uppercase; }
.result-callout p { margin: 0.35rem 0 0; font-size: 0.95rem; }

.approx-tag {
  display: inline-block;
  padding: 0.05rem 0.5rem;
  margin-left: 0.55rem;
  border: 1px solid color-mix(in srgb, var(--pine) 35%, transparent);
  border-radius: 999px;
  color: var(--muted);
  background: var(--panel);
  font-family: var(--mono);
  font-size: 0.7rem;
  vertical-align: 0.1rem;
}

.report-box {
  position: relative;
  padding: 0.95rem 1.05rem;
  border: 1px solid var(--line);
  border-left: 3px solid var(--sky);
  border-radius: var(--r-md);
  background: var(--sky-soft);
}

.report-box p { max-width: none; margin: 0 0 0.6rem; font-size: 0.94rem; }

.code-block {
  overflow: hidden;
  border: 1px solid var(--code-line);
  border-radius: var(--r-md);
  background: var(--code-bg);
}

.code-toolbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.4rem 0.6rem 0.4rem 0.95rem;
  border-bottom: 1px solid var(--code-line);
  color: var(--code-muted);
  font-family: var(--mono);
  font-size: 0.74rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.code-toolbar .button { border-color: var(--code-line); color: var(--code-ink); background: transparent; }
.code-toolbar .button:hover { border-color: var(--code-muted); background: rgb(255 255 255 / 6%); }

.code-block pre {
  max-height: 34rem;
  padding: 0.95rem;
  margin: 0;
  overflow: auto;
  color: var(--code-ink);
  font-size: 0.84rem;
  line-height: 1.65;
  tab-size: 4;
  scrollbar-width: thin;
}

.reference-list { padding-left: 1.1rem; margin: 0; }
.reference-list li { margin-bottom: 0.3rem; }

.method-pager {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.7rem;
  padding-top: 1.4rem;
  margin-top: 2.4rem;
  border-top: 1px solid var(--line);
}

.pager-link {
  display: grid;
  gap: 0.15rem;
  padding: 0.75rem 0.95rem;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  background: var(--panel);
  color: inherit;
  text-decoration: none;
}

.pager-link:hover { border-color: var(--pine); }
.pager-link small { color: var(--faint); font-family: var(--mono); font-size: 0.7rem; letter-spacing: 0.1em; text-transform: uppercase; }
.pager-link span { color: var(--pine-strong); font-weight: 650; font-size: 0.92rem; }
.pager-link.is-next { text-align: right; }

/* ---------- help page: story ---------- */

.p-alpha-story { margin-bottom: 2.4rem; }

.p-alpha-story > header { margin-bottom: 1.1rem; }

.story-step-nav {
  display: grid;
  grid-template-columns: repeat(5, minmax(0, 1fr));
  gap: 0.45rem;
  margin-bottom: 0.8rem;
}

.story-step-nav button {
  display: flex;
  gap: 0.5rem;
  align-items: center;
  min-width: 0;
  padding: 0.5rem 0.65rem;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  background: var(--panel);
  color: var(--muted);
  font: inherit;
  font-size: 0.8rem;
  line-height: 1.3;
  text-align: left;
  cursor: pointer;
}

.story-step-nav button span {
  display: grid;
  flex-shrink: 0;
  place-items: center;
  width: 1.5rem;
  height: 1.5rem;
  border: 1px solid var(--line-strong);
  border-radius: 50%;
  font-family: var(--mono);
  font-size: 0.75rem;
  font-weight: 700;
}

.story-step-nav button small {
  overflow: hidden;
  font-size: 0.78rem;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.story-step-nav button:hover { border-color: var(--pine); color: var(--pine-strong); }

.story-step-nav button[aria-pressed="true"] {
  border-color: var(--pine);
  color: var(--pine-strong);
  background: var(--pine-faint);
}

.story-step-nav button[aria-pressed="true"] span {
  border-color: var(--pine);
  color: var(--on-pine);
  background: var(--pine);
}

.story-stage {
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  background: var(--panel);
  box-shadow: var(--shadow-1);
}

.story-panel {
  display: grid;
  grid-template-columns: minmax(0, 1.05fr) minmax(0, 1fr);
  gap: 1.4rem;
  padding: clamp(1rem, 2.6vw, 1.6rem);
}

.story-counter { color: var(--faint); font-family: var(--mono); font-size: 0.74rem; letter-spacing: 0.1em; }

.story-callout {
  padding: 0.7rem 0.85rem;
  margin-top: 0.9rem;
  border-left: 3px solid var(--pine);
  border-radius: 0 var(--r-sm) var(--r-sm) 0;
  background: var(--pine-faint);
  color: var(--pine-strong);
  font-size: 0.9rem;
  font-weight: 550;
}

.story-visual {
  display: grid;
  align-content: center;
  gap: 0.8rem;
  min-width: 0;
  padding: 0.9rem;
  border: 1px dashed var(--line-strong);
  border-radius: var(--r-md);
  background: var(--panel-soft);
}

.story-visual .formula { overflow-x: auto; }

.story-flow {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  align-items: center;
  justify-content: center;
}

.story-flow span {
  padding: 0.4rem 0.7rem;
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  background: var(--panel);
  font-size: 0.84rem;
}

.story-flow b { color: var(--pine); }

.story-alpha-grid {
  display: grid;
  grid-template-columns: repeat(20, minmax(0, 1fr));
  gap: 0.18rem;
  margin-bottom: 0.4rem;
}

.story-alpha-grid i {
  aspect-ratio: 1;
  border-radius: 50%;
  background: var(--pine-soft);
}

.story-alpha-grid i.is-alpha { background: var(--rust); }

.story-observations {
  display: grid;
  grid-template-columns: repeat(12, minmax(0, 1fr));
  gap: 0.3rem;
}

.story-observations span {
  display: grid;
  place-items: center;
  aspect-ratio: 1;
  border-radius: var(--r-sm);
  font-family: var(--mono);
  font-weight: 700;
}

.story-observations .is-positive { color: var(--pine-strong); background: var(--pine-soft); }
.story-observations .is-negative { color: var(--rust); background: var(--rust-soft); }

.story-binomial-chart { min-width: 0; }

.story-comparison {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  align-items: center;
  justify-content: center;
  font-family: var(--mono);
  font-size: 1.05rem;
  font-weight: 700;
}

.story-comparison span {
  padding: 0.5rem 0.9rem;
  border: 1px solid var(--line);
  border-radius: var(--r-sm);
  background: var(--panel);
}

.story-comparison b { color: var(--pine); font-size: 1.3rem; }

.story-actions {
  display: flex;
  gap: 0.8rem;
  align-items: center;
  justify-content: space-between;
  margin-top: 0.8rem;
}

#story-progress { color: var(--faint); font-family: var(--mono); font-size: 0.8rem; }

/* ---------- help page: lab ---------- */

.p-alpha-topic { margin-bottom: 2.4rem; }
.p-alpha-header { margin-bottom: 1.1rem; }

.p-alpha-lab {
  display: grid;
  gap: 1.1rem;
  padding: clamp(1rem, 2.6vw, 1.5rem);
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  background: var(--panel);
  box-shadow: var(--shadow-1);
}

.lab-controls {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(14rem, 1fr));
  gap: 0.8rem 1.2rem;
}

.lab-control { display: grid; gap: 0.35rem; font-size: 0.86rem; color: var(--muted); }
.lab-control > span { display: flex; justify-content: space-between; gap: 0.6rem; font-weight: 600; }
.lab-control output { color: var(--pine-strong); font-family: var(--mono); }

.lab-control select {
  min-height: 2.5rem;
  padding: 0.35rem 0.6rem;
  border: 1px solid var(--line-strong);
  border-radius: var(--r-sm);
  color: var(--ink-strong);
  background: var(--panel-soft);
  font: inherit;
  font-size: 0.88rem;
}

.lab-control input[type="range"] { width: 100%; accent-color: var(--pine); }

.lab-readout {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(11rem, 1fr));
  gap: 0.6rem;
}

.lab-readout > div {
  display: grid;
  gap: 0.15rem;
  padding: 0.65rem 0.85rem;
  border: 1px solid var(--line);
  border-radius: var(--r-md);
  background: var(--panel-soft);
}

.lab-readout span { color: var(--faint); font-size: 0.76rem; }
.lab-readout strong { font-family: var(--mono); font-size: 1.05rem; color: var(--ink-strong); }
.lab-readout strong.is-reject { color: var(--rust); }
.lab-readout strong.is-retain { color: var(--pine-strong); }

.lab-figure { margin: 0; }

.lab-figure figcaption {
  display: flex;
  flex-wrap: wrap;
  gap: 1.2rem;
  padding-top: 0.5rem;
  color: var(--muted);
  font-size: 0.8rem;
}

.lab-legend-item { display: inline-flex; gap: 0.4rem; align-items: center; }
.lab-legend-item i { width: 0.95rem; height: 0.7rem; border-radius: 2px; }
.lab-legend-item.p-region i { background: var(--sky-soft); border: 1px solid var(--sky); }
.lab-legend-item.alpha-region i { background: repeating-linear-gradient(45deg, transparent 0 2px, var(--rust) 2px 4px); opacity: 0.75; }

.lab-chart { display: block; width: 100%; height: auto; }

.lab-axis, .lab-tick { stroke: var(--line-strong); stroke-width: 1.5; }
.lab-density-line { fill: none; stroke: var(--ink-strong); stroke-width: 2.5; }
.lab-p-area { fill: var(--sky-soft); opacity: 0.92; }
.lab-alpha-area { stroke: var(--rust); stroke-width: 1; }
.alpha-hatch-line { stroke: var(--rust); stroke-width: 3; opacity: 0.6; }
.lab-observed-line { stroke: var(--sky); stroke-width: 2.5; }
.lab-observed-text, .lab-tick-label { fill: var(--ink); font-family: var(--sans); font-size: 13px; }
.lab-observed-text { font-weight: 700; text-anchor: middle; }
.lab-tick-label { text-anchor: middle; }

.lab-discrete-bar { fill: var(--panel-soft); stroke: var(--sky); stroke-width: 1; }
.lab-discrete-bar.in-p { fill: var(--sky-soft); stroke-width: 2; }
.lab-discrete-bar.is-rejection { stroke: var(--rust); stroke-width: 3; stroke-dasharray: 5 3; }
.lab-discrete-bar.is-observed { fill: var(--pine-soft); stroke: var(--pine); stroke-width: 3; }

.lab-explanation {
  padding: 0.9rem 1rem;
  border-left: 3px solid var(--sky);
  border-radius: 0 var(--r-sm) var(--r-sm) 0;
  background: var(--sky-soft);
  font-size: 0.92rem;
}

.lab-explanation .formula { margin-bottom: 0.6rem; }

.lab-concepts ol { padding-left: 1.2rem; margin: 0 0 0.9rem; }
.lab-concepts li { margin-bottom: 0.35rem; font-size: 0.94rem; }

.lab-simulation {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 0.8rem 1.2rem;
  align-items: center;
  padding: 0.95rem 1rem;
  border: 1px dashed var(--line-strong);
  border-radius: var(--r-md);
  background: var(--panel-soft);
}

.lab-simulation h3 { margin-bottom: 0.25rem; }
.lab-simulation p { margin: 0; color: var(--muted); font-size: 0.86rem; }

.sim-summary { grid-column: 1 / -1; color: var(--ink-strong); font-family: var(--mono); font-size: 0.85rem; }

.sim-grid {
  display: grid;
  grid-column: 1 / -1;
  grid-template-columns: repeat(20, minmax(0, 1fr));
  gap: 0.15rem;
}

.sim-dot {
  display: grid;
  place-items: center;
  min-height: 1.05rem;
  color: var(--pine);
  font-family: var(--mono);
  font-weight: 700;
  line-height: 1;
}

.sim-dot.is-reject { color: var(--rust); }

.p-alpha-reading { margin-bottom: 2.4rem; }

/* ---------- help cards ---------- */

.help-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.8rem;
}

.help-card {
  padding: 1.05rem 1.15rem;
  border: 1px solid var(--line);
  border-radius: var(--r-lg);
  background: var(--panel);
  scroll-margin-top: calc(var(--header-h) + 1.25rem);
}

.help-card h2 { padding-bottom: 0.4rem; margin-bottom: 0.7rem; font-size: 1.05rem; border-bottom: 1px solid var(--line); }

.help-card:target { border-color: var(--pine); box-shadow: 0 0 0 3px color-mix(in srgb, var(--pine) 16%, transparent); }

/* ---------- responsive ---------- */

@media (max-width: 1020px) {
  .explorer-layout { grid-template-columns: 1fr; }

  .guidance-rail {
    position: static;
    max-height: none;
    order: -1;
  }

  .story-panel { grid-template-columns: 1fr; }
}

@media (max-width: 900px) {
  .method-layout { grid-template-columns: 1fr; gap: 0.6rem; }

  .method-toc {
    position: static;
    max-height: none;
    padding: 0.35rem 0;
    margin-bottom: 0.8rem;
    border-bottom: 1px solid var(--line);
  }

  .method-toc nav {
    display: flex;
    gap: 0.25rem;
    overflow-x: auto;
    padding-bottom: 0.45rem;
    scrollbar-width: thin;
  }

  .method-toc a { flex-shrink: 0; padding: 0.3rem 0.6rem; border: 1px solid var(--line); border-radius: 999px; }
  .method-toc a[data-active] { border-color: var(--pine); background: var(--pine-faint); }
  .toc-label { display: none; }
}

@media (max-width: 760px) {
  .header-inner { flex-wrap: wrap; padding-block: 0.6rem; gap: 0.5rem 0.9rem; }
  .brand { margin-right: 0; flex: 1 1 auto; }
  .site-nav { order: 3; width: 100%; }
  .brand-copy span { display: none; }
  .palette-button span:not(.palette-button-glyph) { display: none; }
  .palette-button kbd { display: none; }

  .story-step-nav { grid-template-columns: repeat(auto-fit, minmax(3rem, 1fr)); }
  .story-step-nav button small { display: none; }
  .story-step-nav button { justify-content: center; }

  .help-grid { grid-template-columns: 1fr; }
  .lab-simulation { grid-template-columns: 1fr; }
  .method-pager { grid-template-columns: 1fr; }
  .pager-link.is-next { text-align: left; }

  .footer-inner a { margin-left: 0; }
}

/* ---------- motion & print ---------- */

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *,
  *::before,
  *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
}

@media print {
  .site-header, .site-footer, .method-toc, .method-pager, .facet-panel,
  .guidance-rail, .story-step-nav, .story-actions, .lab-controls, .lab-simulation .button {
    display: none !important;
  }

  body { color: #111; background: #fff; }

  .method-layout, .explorer-layout { display: block; }

  .content-section, .formula-card, .lab-figure { break-inside: avoid; }
}