/* ===========================================================================
   shelfanalytics.org — site styles
   Light, elegant retail-analytics theme with widescreen layout.
   =========================================================================== */

/* ---- tokens ------------------------------------------------------------- */
:root {
  --brand-deep:   #134e6f;
  --brand-teal:   #1f9da4;
  --brand-mint:   #6fd1c1;
  --brand-accent: #ff6e3a;
  --brand-gold:   #f2b134;
  --brand-violet: #6a5acd;

  --surface:      #ffffff;
  --surface-2:    #f6f4ef;
  --surface-3:    #eef2f5;
  --page-bg:      #fafaf7;

  --text:         #16263a;
  --text-strong:  #0c1a2b;
  --muted:        #5b6b7a;
  --rule:         #e3e7eb;

  --code-bg:      #f3f6f9;
  --code-text:    #0c1a2b;
  --inline-code-bg: #eef3f7;

  --link:         #1a6b8e;
  --link-hover:   var(--brand-accent);

  --shadow-sm: 0 1px 2px rgba(20, 40, 60, 0.04), 0 1px 3px rgba(20, 40, 60, 0.06);
  --shadow-md: 0 4px 10px rgba(20, 40, 60, 0.06), 0 10px 24px rgba(20, 40, 60, 0.08);
  --shadow-lg: 0 12px 30px rgba(20, 40, 60, 0.10);

  --radius-sm: 6px;
  --radius:    10px;
  --radius-lg: 16px;

  --header-h: 64px;
  --content-max: min(1320px, 92vw);
  --prose-max: 78ch;

  --font-sans: "Inter", "Segoe UI", system-ui, -apple-system, "Helvetica Neue", Arial, sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", "SFMono-Regular", ui-monospace, Menlo, Consolas, monospace;
}

/* ---- reset -------------------------------------------------------------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; }
img, svg, video { display: block; max-width: 100%; }
button { font: inherit; cursor: pointer; }

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

/* ---- page ---------------------------------------------------------------- */
html, body { height: 100%; }
body {
  background: var(--page-bg);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

.page {
  min-height: 100vh;
  display: grid;
  grid-template-rows: auto 1fr auto;
}

main.site-main {
  width: var(--content-max);
  margin: 0 auto;
  padding: 32px 0 64px;
}

/* ---- typography --------------------------------------------------------- */
h1, h2, h3, h4, h5, h6 {
  color: var(--text-strong);
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.01em;
  scroll-margin-top: calc(var(--header-h) + 16px);
}

.page-title {
  font-size: clamp(2rem, 1.4rem + 2.4vw, 3rem);
  margin: 0 0 0.6em;
  background: linear-gradient(92deg, var(--brand-deep), var(--brand-teal) 60%, var(--brand-accent));
  -webkit-background-clip: text;
          background-clip: text;
  color: transparent;
}

.prose h2 {
  font-size: clamp(1.4rem, 1.05rem + 1vw, 1.85rem);
  margin: 2.2em 0 0.6em;
  color: var(--brand-deep);
  border-bottom: 2px solid var(--brand-mint);
  padding-bottom: 0.35em;
}
.prose h3 {
  font-size: 1.25rem;
  margin: 1.8em 0 0.5em;
  color: var(--brand-teal);
}
.prose h4 { font-size: 1.05rem; margin: 1.4em 0 0.4em; color: var(--brand-deep); }
.prose p { margin: 0 0 1.05em; }
.prose ul, .prose ol { padding-left: 1.4em; margin: 0 0 1.1em; }
.prose li { margin: 0.25em 0; }
.prose strong { color: var(--text-strong); }

/* heading anchor link (markdown-it-anchor permalink) */
.prose .header-anchor {
  color: var(--muted);
  margin-left: 0.4em;
  text-decoration: none;
  opacity: 0;
  transition: opacity .15s ease, color .15s ease;
  font-weight: 400;
}
.prose h2:hover .header-anchor,
.prose h3:hover .header-anchor,
.prose h4:hover .header-anchor { opacity: 1; }
.prose .header-anchor:hover { color: var(--brand-accent); }

/* ---- links -------------------------------------------------------------- */
a {
  color: var(--link);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color .15s ease, border-color .15s ease;
}
a:hover, a:focus-visible {
  color: var(--link-hover);
  border-bottom-color: currentColor;
}
.prose a {
  border-bottom: 1px solid rgba(26,107,142,0.35);
}
.prose a:hover { border-bottom-color: var(--brand-accent); }

/* ---- header ------------------------------------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.86);
  -webkit-backdrop-filter: saturate(160%) blur(12px);
          backdrop-filter: saturate(160%) blur(12px);
  border-bottom: 1px solid var(--rule);
}
.site-header__inner {
  width: var(--content-max);
  margin: 0 auto;
  height: var(--header-h);
  display: flex;
  align-items: center;
  gap: 16px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  color: var(--text-strong);
  border: 0;
}
.brand:hover { color: var(--brand-deep); }
.brand svg { width: 36px; height: 36px; }
.brand__name {
  font-size: 1.02rem;
  letter-spacing: -0.01em;
  background: linear-gradient(92deg, var(--brand-deep), var(--brand-teal));
  -webkit-background-clip: text;
          background-clip: text;
  color: transparent;
}

.primary-nav { margin-left: auto; }
.primary-nav ul {
  display: flex;
  list-style: none;
  gap: 4px;
  margin: 0;
  padding: 0;
}
.primary-nav a {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border-radius: 8px;
  color: var(--muted);
  border: 0;
  font-weight: 500;
  font-size: 0.95rem;
  transition: background .15s ease, color .15s ease;
}
.primary-nav a:hover {
  color: var(--brand-deep);
  background: var(--surface-3);
}
.primary-nav a[aria-current="page"] {
  color: var(--brand-deep);
  background: linear-gradient(180deg, rgba(31,157,164,0.10), rgba(19,78,111,0.05));
  box-shadow: inset 0 0 0 1px rgba(31,157,164,0.20);
}
.primary-nav a svg {
  width: 18px; height: 18px;
  stroke: currentColor;
  flex-shrink: 0;
}

.nav-toggle {
  display: none;
  background: transparent;
  border: 1px solid var(--rule);
  border-radius: 8px;
  padding: 6px 10px;
  margin-left: auto;
  color: var(--text-strong);
}

/* ---- footer ------------------------------------------------------------- */
.site-footer {
  background: var(--surface-2);
  border-top: 1px solid var(--rule);
  margin-top: 48px;
}
.site-footer__inner {
  width: var(--content-max);
  margin: 0 auto;
  padding: 32px 0;
  display: grid;
  gap: 24px;
  grid-template-columns: 1.4fr repeat(3, 1fr);
}
.site-footer h4 {
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--brand-deep);
  margin: 0 0 0.6em;
}
.site-footer ul { list-style: none; margin: 0; padding: 0; }
.site-footer li { margin: 0.25em 0; }
.site-footer a { color: var(--muted); border: 0; }
.site-footer a:hover { color: var(--brand-accent); }
.site-footer__brand { display: flex; gap: 12px; align-items: flex-start; }
.site-footer__brand svg { width: 40px; height: 40px; }
.site-footer__brand p { margin: 0; color: var(--muted); font-size: 0.92rem; }
.site-footer__legal {
  width: var(--content-max);
  margin: 0 auto;
  padding: 16px 0 28px;
  color: var(--muted);
  font-size: 0.85rem;
}

/* ---- hero --------------------------------------------------------------- */
.hero {
  padding: 56px 0 24px;
  text-align: center;
}
.hero__logo {
  display: flex;
  justify-content: center;
  margin-bottom: 28px;
}
.hero__logo svg {
  width: clamp(140px, 22vw, 220px);
  height: auto;
  filter: drop-shadow(0 12px 22px rgba(31,157,164,0.18));
  transition: transform .3s ease;
}
.hero__logo:hover svg { transform: translateY(-3px) scale(1.02); }

.hero__title {
  font-size: clamp(2.1rem, 1.4rem + 2.8vw, 3.4rem);
  margin: 0 0 0.5em;
  background: linear-gradient(92deg, var(--brand-deep), var(--brand-teal) 55%, var(--brand-accent));
  -webkit-background-clip: text;
          background-clip: text;
  color: transparent;
  line-height: 1.15;
}
.hero__lede {
  max-width: 68ch;
  margin: 0 auto 1.2em;
  color: var(--muted);
  font-size: 1.08rem;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  justify-content: center;
  margin: 28px 0 8px;
}
.cta {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 12px 18px;
  border-radius: 999px;
  background: var(--surface);
  color: var(--text-strong);
  border: 1px solid var(--rule);
  font-weight: 600;
  box-shadow: var(--shadow-sm);
  transition: transform .15s ease, box-shadow .2s ease, color .15s ease, border-color .15s ease;
}
.cta:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  color: var(--brand-deep);
  border-color: var(--brand-mint);
}
.cta__icon {
  display: inline-grid;
  place-items: center;
  width: 30px; height: 30px;
  border-radius: 8px;
  color: white;
}
.cta__icon svg { width: 18px; height: 18px; stroke: currentColor; }
.cta--core    .cta__icon { background: linear-gradient(135deg, var(--brand-deep), var(--brand-teal)); }
.cta--vision  .cta__icon { background: linear-gradient(135deg, var(--brand-accent), var(--brand-gold)); }
.cta--planogram .cta__icon { background: linear-gradient(135deg, var(--brand-violet), var(--brand-teal)); }

/* ---- section cards ------------------------------------------------------ */
.section-grid {
  display: grid;
  gap: 22px;
  margin: 56px 0;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}
.section-card {
  display: block;
  padding: 24px;
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: var(--radius-lg);
  color: inherit;
  border-bottom: 1px solid var(--rule);
  transition: transform .2s ease, box-shadow .2s ease, border-color .2s ease;
}
.section-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: var(--brand-mint);
  color: inherit;
}
.section-card__icon {
  display: inline-grid;
  place-items: center;
  width: 44px; height: 44px;
  border-radius: 12px;
  margin-bottom: 14px;
  color: white;
}
.section-card__icon svg { width: 22px; height: 22px; stroke: currentColor; }
.section-card--core .section-card__icon    { background: linear-gradient(135deg, var(--brand-deep), var(--brand-teal)); }
.section-card--vision .section-card__icon  { background: linear-gradient(135deg, var(--brand-accent), var(--brand-gold)); }
.section-card--planogram .section-card__icon { background: linear-gradient(135deg, var(--brand-violet), var(--brand-teal)); }
.section-card h3 { margin: 0 0 0.4em; color: var(--brand-deep); }
.section-card p  { margin: 0; color: var(--muted); }

/* ---- prose container ---------------------------------------------------- */
.article-shell {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 28px;
}
@media (min-width: 1100px) {
  .article-shell {
    grid-template-columns: minmax(0, 1fr) 280px;
    align-items: start;
  }
}

.prose {
  max-width: 100%;
}
.prose > * { max-width: 100%; }

/* ---- breadcrumbs -------------------------------------------------------- */
.breadcrumbs {
  font-size: 0.9rem;
  color: var(--muted);
  margin: 8px 0 18px;
}
.breadcrumbs ol {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin: 0; padding: 0;
}
.breadcrumbs li + li::before {
  content: "›";
  color: var(--rule);
  margin-right: 6px;
}
.breadcrumbs a { color: var(--muted); border: 0; }
.breadcrumbs a:hover { color: var(--brand-accent); }
.breadcrumbs [aria-current="page"] { color: var(--brand-deep); font-weight: 600; }

/* ---- related panel ------------------------------------------------------ */
.related-panel {
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 20px;
  position: sticky;
  top: calc(var(--header-h) + 16px);
}
.related-panel h2 {
  margin: 0 0 0.6em;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--brand-deep);
  border: 0;
  padding: 0;
}
.related-panel ul { list-style: none; margin: 0; padding: 0; }
.related-panel li { margin: 6px 0; }
.related-panel a {
  display: block;
  padding: 6px 8px;
  border-radius: 6px;
  color: var(--text);
  border: 0;
  font-size: 0.94rem;
}
.related-panel a:hover { background: var(--surface-3); color: var(--brand-deep); }

/* ---- code blocks -------------------------------------------------------- */
.codeblock {
  position: relative;
  margin: 1.2em 0;
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  background: var(--code-bg);
  overflow: hidden;
}
.codeblock pre {
  margin: 0;
  padding: 16px 18px;
  overflow: auto;
  font-family: var(--font-mono);
  font-size: 0.92rem;
  line-height: 1.55;
  color: var(--code-text);
  background: transparent;
}
.codeblock pre code { background: transparent; padding: 0; }
.codeblock-copy {
  position: absolute;
  top: 8px;
  right: 8px;
  border: 1px solid var(--rule);
  background: var(--surface);
  color: var(--muted);
  border-radius: 6px;
  padding: 4px 10px;
  font-size: 0.78rem;
  font-weight: 600;
  opacity: 0;
  transition: opacity .15s ease, color .15s ease, border-color .15s ease;
}
.codeblock:hover .codeblock-copy,
.codeblock:focus-within .codeblock-copy { opacity: 1; }
.codeblock-copy:hover { color: var(--brand-deep); border-color: var(--brand-mint); }
.codeblock-copy.is-copied { color: var(--brand-teal); border-color: var(--brand-mint); }

/* inline code */
.prose :not(pre) > code {
  background: var(--inline-code-bg);
  color: var(--text-strong);
  border-radius: 4px;
  padding: 0.05em 0.4em;
  font-family: var(--font-mono);
  font-size: 0.93em;
  border: 0;
}

/* prism light theme tweaks */
.codeblock .token.comment,
.codeblock .token.prolog,
.codeblock .token.doctype,
.codeblock .token.cdata { color: #7d8a96; font-style: italic; }
.codeblock .token.punctuation { color: #4d5b69; }
.codeblock .token.property,
.codeblock .token.tag,
.codeblock .token.boolean,
.codeblock .token.number,
.codeblock .token.constant,
.codeblock .token.symbol,
.codeblock .token.deleted { color: var(--brand-violet); }
.codeblock .token.selector,
.codeblock .token.attr-name,
.codeblock .token.string,
.codeblock .token.char,
.codeblock .token.builtin,
.codeblock .token.inserted { color: #1f7a52; }
.codeblock .token.operator,
.codeblock .token.entity,
.codeblock .token.url,
.codeblock .language-css .token.string,
.codeblock .style .token.string { color: var(--brand-accent); }
.codeblock .token.atrule,
.codeblock .token.attr-value,
.codeblock .token.keyword { color: var(--brand-deep); font-weight: 600; }
.codeblock .token.function,
.codeblock .token.class-name { color: var(--brand-teal); }
.codeblock .token.regex,
.codeblock .token.important,
.codeblock .token.variable { color: var(--brand-gold); }

/* ---- tables ------------------------------------------------------------- */
.table-scroll {
  width: 100%;
  overflow-x: auto;
  margin: 1.4em 0;
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  background: var(--surface);
}
.table-scroll table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
}
.table-scroll th, .table-scroll td {
  text-align: left;
  padding: 10px 14px;
  border-bottom: 1px solid var(--rule);
  vertical-align: top;
}
.table-scroll th {
  background: var(--surface-2);
  color: var(--brand-deep);
  font-weight: 700;
  border-bottom: 2px solid var(--brand-mint);
}
.table-scroll tr:last-child td { border-bottom: 0; }
.table-scroll tr:nth-child(even) td { background: rgba(238, 242, 245, 0.4); }

/* ---- task list (interactive checkboxes) -------------------------------- */
.task-list { list-style: none; padding-left: 0; }
.task-list-item {
  list-style: none;
  position: relative;
  padding-left: 1.9em;
  margin: 0.4em 0;
  transition: color .15s ease;
}
.task-list-item::marker { content: ""; }
.task-list-item > input[type="checkbox"] {
  position: absolute;
  left: 0;
  top: 0.35em;
  width: 1.05em;
  height: 1.05em;
  margin: 0;
  accent-color: var(--brand-teal);
  cursor: pointer;
}
.task-list-item.is-checked {
  color: var(--muted);
  text-decoration: line-through;
}

/* ---- accordion (FAQ) ---------------------------------------------------- */
details.faq {
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  background: var(--surface);
  margin: 10px 0;
  transition: box-shadow .2s ease, border-color .2s ease;
}
details.faq[open] {
  box-shadow: var(--shadow-sm);
  border-color: var(--brand-mint);
}
details.faq > summary {
  cursor: pointer;
  list-style: none;
  padding: 14px 18px;
  font-weight: 600;
  color: var(--brand-deep);
  display: flex;
  align-items: center;
  gap: 10px;
}
details.faq > summary::-webkit-details-marker { display: none; }
details.faq > summary::before {
  content: "";
  width: 12px; height: 12px;
  border-right: 2px solid var(--brand-teal);
  border-bottom: 2px solid var(--brand-teal);
  transform: rotate(-45deg);
  transition: transform .2s ease;
  flex-shrink: 0;
}
details.faq[open] > summary::before { transform: rotate(45deg); }
details.faq > .faq-body { padding: 0 18px 14px; color: var(--text); }

/* ---- mermaid ------------------------------------------------------------ */
.mermaid {
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  padding: 18px;
  margin: 1.4em 0;
  text-align: center;
  overflow-x: auto;
}

/* ---- katex tweaks ------------------------------------------------------- */
.katex { font-size: 1.05em; }
.katex-display { overflow-x: auto; padding: 8px 0; }

/* ---- back-to-top -------------------------------------------------------- */
.back-to-top {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-top: 36px;
  font-size: 0.92rem;
  color: var(--muted);
}
.back-to-top .icon { width: 16px; height: 16px; flex-shrink: 0; }

/* Safety: any unsized inline icon used inside prose stays compact */
.prose .icon { width: 1.05em; height: 1.05em; vertical-align: -0.15em; display: inline-block; }

/* ---- responsive --------------------------------------------------------- */
@media (max-width: 880px) {
  :root { --header-h: 56px; }
  .nav-toggle { display: inline-flex; }
  .primary-nav {
    position: absolute;
    top: var(--header-h);
    left: 0; right: 0;
    background: var(--surface);
    border-bottom: 1px solid var(--rule);
    padding: 12px 0;
    display: none;
  }
  .primary-nav[data-open="true"] { display: block; }
  .primary-nav ul {
    flex-direction: column;
    width: var(--content-max);
    margin: 0 auto;
    gap: 0;
  }
  .primary-nav a { padding: 12px 8px; }
  .site-footer__inner { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 540px) {
  body { font-size: 16px; }
  .site-footer__inner { grid-template-columns: 1fr; }
  main.site-main { padding: 18px 0 40px; }
  .hero { padding: 32px 0 12px; }
}