/* ============================================================
   Self-hosted fonts — mirrored from Google Fonts (same files,
   same unicode-range subsetting) so no cross-origin, render-
   blocking request is needed. Licences: OFL (IBM Plex,
   Instrument Serif).
============================================================ */
/* The IBM Plex Sans woff2 files are VARIABLE fonts (wght 100-700):
   one file per subset serves weights 400/500/600/700. */
/* cyrillic-ext */
@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/ibm-plex-mono-normal-400-cyrillic-ext.woff2) format('woff2');
  unicode-range: U+0460-052F, U+1C80-1C8A, U+20B4, U+2DE0-2DFF, U+A640-A69F, U+FE2E-FE2F;
}
/* cyrillic */
@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/ibm-plex-mono-normal-400-cyrillic.woff2) format('woff2');
  unicode-range: U+0301, U+0400-045F, U+0490-0491, U+04B0-04B1, U+2116;
}
/* vietnamese */
@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/ibm-plex-mono-normal-400-vietnamese.woff2) format('woff2');
  unicode-range: U+0102-0103, U+0110-0111, U+0128-0129, U+0168-0169, U+01A0-01A1, U+01AF-01B0, U+0300-0301, U+0303-0304, U+0308-0309, U+0323, U+0329, U+1EA0-1EF9, U+20AB;
}
/* latin-ext */
@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/ibm-plex-mono-normal-400-latin-ext.woff2) format('woff2');
  unicode-range: U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304, U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}
/* latin */
@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/ibm-plex-mono-normal-400-latin.woff2) format('woff2');
  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}
/* cyrillic-ext */
@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 500;
  font-display: swap;
  src: url(/fonts/ibm-plex-mono-normal-500-cyrillic-ext.woff2) format('woff2');
  unicode-range: U+0460-052F, U+1C80-1C8A, U+20B4, U+2DE0-2DFF, U+A640-A69F, U+FE2E-FE2F;
}
/* cyrillic */
@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 500;
  font-display: swap;
  src: url(/fonts/ibm-plex-mono-normal-500-cyrillic.woff2) format('woff2');
  unicode-range: U+0301, U+0400-045F, U+0490-0491, U+04B0-04B1, U+2116;
}
/* vietnamese */
@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 500;
  font-display: swap;
  src: url(/fonts/ibm-plex-mono-normal-500-vietnamese.woff2) format('woff2');
  unicode-range: U+0102-0103, U+0110-0111, U+0128-0129, U+0168-0169, U+01A0-01A1, U+01AF-01B0, U+0300-0301, U+0303-0304, U+0308-0309, U+0323, U+0329, U+1EA0-1EF9, U+20AB;
}
/* latin-ext */
@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 500;
  font-display: swap;
  src: url(/fonts/ibm-plex-mono-normal-500-latin-ext.woff2) format('woff2');
  unicode-range: U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304, U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}
/* latin */
@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 500;
  font-display: swap;
  src: url(/fonts/ibm-plex-mono-normal-500-latin.woff2) format('woff2');
  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}
/* cyrillic-ext */
@font-face {
  font-family: 'IBM Plex Sans';
  font-style: normal;
  font-weight: 100 700;
  font-stretch: 100%;
  font-display: swap;
  src: url(/fonts/ibm-plex-sans-variable-cyrillic-ext.woff2) format('woff2');
  unicode-range: U+0460-052F, U+1C80-1C8A, U+20B4, U+2DE0-2DFF, U+A640-A69F, U+FE2E-FE2F;
}
/* cyrillic */
@font-face {
  font-family: 'IBM Plex Sans';
  font-style: normal;
  font-weight: 100 700;
  font-stretch: 100%;
  font-display: swap;
  src: url(/fonts/ibm-plex-sans-variable-cyrillic.woff2) format('woff2');
  unicode-range: U+0301, U+0400-045F, U+0490-0491, U+04B0-04B1, U+2116;
}
/* greek */
@font-face {
  font-family: 'IBM Plex Sans';
  font-style: normal;
  font-weight: 100 700;
  font-stretch: 100%;
  font-display: swap;
  src: url(/fonts/ibm-plex-sans-variable-greek.woff2) format('woff2');
  unicode-range: U+0370-0377, U+037A-037F, U+0384-038A, U+038C, U+038E-03A1, U+03A3-03FF;
}
/* vietnamese */
@font-face {
  font-family: 'IBM Plex Sans';
  font-style: normal;
  font-weight: 100 700;
  font-stretch: 100%;
  font-display: swap;
  src: url(/fonts/ibm-plex-sans-variable-vietnamese.woff2) format('woff2');
  unicode-range: U+0102-0103, U+0110-0111, U+0128-0129, U+0168-0169, U+01A0-01A1, U+01AF-01B0, U+0300-0301, U+0303-0304, U+0308-0309, U+0323, U+0329, U+1EA0-1EF9, U+20AB;
}
/* latin-ext */
@font-face {
  font-family: 'IBM Plex Sans';
  font-style: normal;
  font-weight: 100 700;
  font-stretch: 100%;
  font-display: swap;
  src: url(/fonts/ibm-plex-sans-variable-latin-ext.woff2) format('woff2');
  unicode-range: U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304, U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}
/* latin */
@font-face {
  font-family: 'IBM Plex Sans';
  font-style: normal;
  font-weight: 100 700;
  font-stretch: 100%;
  font-display: swap;
  src: url(/fonts/ibm-plex-sans-variable-latin.woff2) format('woff2');
  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}
/* sub- and superscripts (₂ ⁴ ⁺ ⁻ …) for the Unicode formulae in figures. Not a Google Fonts
   cut: built by _scripts/build-plex-scripts-font.py from the OFL Plex sources, with ⁺ and ⁻
   drawn from Plex's own + and − (Plex has neither). Without these faces H₂O fell back to a
   system font, small and low (Joe 2026-10-01). */
@font-face {
  font-family: 'IBM Plex Sans';
  font-style: normal;
  font-weight: 100 700;
  font-stretch: 100%;
  font-display: swap;
  src: url(/fonts/ibm-plex-sans-variable-scripts.woff2) format('woff2');
  unicode-range: U+2070, U+2074-207B, U+2080-2089;
}
@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/ibm-plex-mono-normal-400-scripts.woff2) format('woff2');
  unicode-range: U+2070, U+2074-207B, U+2080-2089;
}
@font-face {
  font-family: 'IBM Plex Mono';
  font-style: normal;
  font-weight: 500;
  font-display: swap;
  src: url(/fonts/ibm-plex-mono-normal-500-scripts.woff2) format('woff2');
  unicode-range: U+2070, U+2074-207B, U+2080-2089;
}
/* latin-ext */
@font-face {
  font-family: 'Instrument Serif';
  font-style: italic;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/instrument-serif-italic-400-latin-ext.woff2) format('woff2');
  unicode-range: U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304, U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}
/* latin */
@font-face {
  font-family: 'Instrument Serif';
  font-style: italic;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/instrument-serif-italic-400-latin.woff2) format('woff2');
  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}
/* latin-ext */
@font-face {
  font-family: 'Instrument Serif';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/instrument-serif-normal-400-latin-ext.woff2) format('woff2');
  unicode-range: U+0100-02BA, U+02BD-02C5, U+02C7-02CC, U+02CE-02D7, U+02DD-02FF, U+0304, U+0308, U+0329, U+1D00-1DBF, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF;
}
/* latin */
@font-face {
  font-family: 'Instrument Serif';
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url(/fonts/instrument-serif-normal-400-latin.woff2) format('woff2');
  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD;
}
/* ============================================================
   Whiteboard Chemistry — Redesigned Stylesheet
   "Quiet authority, examiner-led"
============================================================ */

:root {
  /* Palette — Ink & Oxide (default) */
  --paper:      oklch(0.975 0.005 80);
  --paper-2:    oklch(0.955 0.008 80);
  --paper-3:    oklch(0.92  0.01  80);
  --ink:        oklch(0.20  0.018 250);
  --ink-soft:   oklch(0.32  0.015 250);
  --muted:      oklch(0.50  0.012 250);
  --hairline:   oklch(0.88  0.01  250);
  --accent:     oklch(0.52  0.165 30);
  --accent-soft:oklch(0.62  0.14  30);
  --dark:       oklch(0.16  0.018 250);

  --maxw: 1240px;
  --gutter: clamp(20px, 4vw, 56px);

  /* The whiteboard grid-paper ground — ONE definition for every surface
     that carries it (hero, proof bar, dark CTA, utility heroes). Pair with
     background-size: 64px 64px and a per-surface mask. */
  --grid-paper-ink:
    linear-gradient(to right, color-mix(in srgb, var(--ink) 4%, transparent) 1px, transparent 1px),
    linear-gradient(to bottom, color-mix(in srgb, var(--ink) 4%, transparent) 1px, transparent 1px);
  --grid-paper-light:
    linear-gradient(to right, color-mix(in srgb, var(--paper) 4%, transparent) 1px, transparent 1px),
    linear-gradient(to bottom, color-mix(in srgb, var(--paper) 4%, transparent) 1px, transparent 1px);
  --radius: 4px;

  --font-display: "Instrument Serif", "EB Garamond", Georgia, serif;
  --font-body:    "IBM Plex Sans", "Helvetica Neue", Helvetica, sans-serif;
  --font-mono:    "IBM Plex Mono", ui-monospace, monospace;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 80px; } /* R3 item 16: focus never lands under the sticky header */
body {
  margin: 0;
  font-family: var(--font-body);
  font-weight: 400;
  font-size: 17px;
  line-height: 1.55;
  color: var(--ink);
  background: var(--paper);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  /* Defensive: nothing on these pages should scroll the page horizontally.
     Safe on body — the viewport (not body) is the scroll container, so
     position:sticky on .header/.rn-toc still works and the fixed nav drawer
     is unaffected. */
  overflow-x: hidden;
}

img { max-width: 100%; display: block; }

.wrap {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0 var(--gutter);
}

/* Skip link — first element in <body>; invisible until a keyboard user
   focuses it, then a paper-on-ink pill in the top-left corner.
   Hidden-by-default with a :focus reveal — NOT :not(:focus-visible) —
   because engines without :focus-visible drop any rule whose selector
   contains it, which would leave the pill permanently visible. */
.skip-link {
  position: fixed;
  top: 16px;
  left: 16px;
  z-index: 3000;
  display: inline-flex;
  align-items: center;
  background: var(--ink);
  color: var(--paper);
  font-family: var(--font-body);
  font-size: 14px;
  font-weight: 500;
  line-height: 1;
  text-decoration: none;
  /* sr-only until focused */
  width: 1px;
  height: 1px;
  padding: 0;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}
.skip-link:focus {
  width: auto;
  height: auto;
  padding: 13px 22px;
  border-radius: 999px;
  overflow: visible;
  clip-path: none;
}

/* ============================================================
   HEADER
============================================================ */
.header {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: var(--paper);
  border-bottom: 1px solid transparent;
  transition: border-color .2s ease, box-shadow .2s ease, background .2s ease;
}
.header.is-scrolled {
  border-bottom-color: var(--hairline);
  background: color-mix(in srgb, var(--paper) 92%, transparent);
  backdrop-filter: blur(8px);
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px var(--gutter);
  max-width: var(--maxw);
  margin: 0 auto;
}
.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--ink);
  text-decoration: none;
}
.brand-mark {
  display: inline-flex;
  width: 36px; height: 36px;
  align-items: center; justify-content: center;
  color: var(--ink);
  background: transparent;
}
.brand-mark svg { width: 32px; height: 32px; } /* LOGO C (Joe, 2026-10-08): mark a touch larger, closer to the wordmark */
.brand-text { display: flex; flex-direction: column; line-height: 1; }
.brand-name {
  font-family: var(--font-display);
  font-size: 22px;
  letter-spacing: -0.01em;
}
.brand-sub { /* footer lockup only since LOGO C: the header carries no byline */
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--muted);
  margin-top: 4px;
}
.nav {
  display: flex;
  align-items: center;
  gap: 26px;
}
.nav a {
  font-size: 14.5px;
  color: var(--ink-soft);
  text-decoration: none;
  font-weight: 500;
  transition: color .15s;
}
.nav a:hover { color: var(--ink); }
.nav-cta {
  background: var(--ink);
  color: var(--paper) !important;
  padding: 10px 18px;
  border-radius: 999px;
  font-weight: 500;
  font-size: 14px;
  white-space: nowrap;
  transition: background .15s;
}
.nav-cta:hover { background: var(--accent); color: var(--paper) !important; }

/* ============================================================
   HERO
============================================================ */
.hero {
  padding: clamp(24px, 3.2vw, 48px) 0 clamp(48px, 7vw, 96px);
  position: relative;
  overflow: hidden;
}
.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: var(--grid-paper-ink);
  background-size: 64px 64px;
  mask-image: radial-gradient(ellipse at top right, black 0%, black 30%, transparent 75%);
  pointer-events: none;
}
.hero-grid {
  position: relative;
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: clamp(32px, 6vw, 80px);
  align-items: center;
}
.kicker {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.04em;
  color: var(--muted);
  text-transform: uppercase;
  margin-bottom: 28px;
}
.kicker-dot {
  width: 6px; height: 6px; border-radius: 50%;
  background: var(--accent);
}

.display {
  font-family: var(--font-display);
  font-weight: 400;
  font-size: clamp(48px, 7.5vw, 104px);
  line-height: 0.95;
  letter-spacing: -0.025em;
  margin: 0 0 24px;
  color: var(--ink);
}
.display em.accent {
  font-style: italic;
  color: var(--accent);
  font-weight: 400;
}

.lede {
  font-size: clamp(18px, 1.4vw, 21px);
  line-height: 1.5;
  color: var(--ink-soft);
  max-width: 50ch;
  margin: 0 0 36px;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  align-items: center;
  margin-bottom: 28px;
}

.btn {
  --btn-h: 52px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  height: var(--btn-h);
  padding: 0 22px;
  border-radius: 999px;
  font-size: 15px;
  font-weight: 500;
  text-decoration: none;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform .15s ease, background .15s, color .15s, border-color .15s;
  font-family: var(--font-body);
  white-space: nowrap;
}
.btn:hover { transform: translateY(-1px); }
.btn-primary {
  background: var(--ink);
  color: var(--paper);
}
.btn-primary:hover { background: var(--accent); }
.btn-ghost {
  background: transparent;
  color: var(--ink);
  border-color: var(--hairline);
}
.btn-ghost:hover { border-color: var(--ink); }
.btn-light {
  background: var(--paper);
  color: var(--ink);
}
.btn-light:hover { background: var(--accent); color: var(--paper); }
.btn-ghost-light {
  background: transparent;
  color: var(--paper);
  border-color: color-mix(in srgb, var(--paper) 40%, transparent);
}
.btn-ghost-light:hover { border-color: var(--paper); }
.btn-large { --btn-h: 60px; padding: 0 28px; font-size: 16px; }
.btn-block { width: 100%; }
.btn-arrow {
  font-size: 18px;
  transition: transform .2s ease;
}
.btn:hover .btn-arrow { transform: translateX(3px); }

.micro-proof {
  display: block;
  position: relative;
  padding-left: 18px;
  font-size: 13.5px;
  line-height: 1.5;
  color: var(--muted);
  margin: 0;
  font-family: var(--font-mono);
}
.micro-proof + .micro-proof { margin-top: 8px; }
.micro-proof strong {
  color: var(--ink);
  font-weight: 500;
}
.micro-proof .dot {
  position: absolute;
  left: 0;
  top: 0.5em;
  width: 8px; height: 8px;
  border-radius: 50%;
  background: var(--accent);
  animation: pulse 2.2s ease-in-out infinite;
}
@keyframes pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.4; transform: scale(0.8); }
}

/* Hero photo */
.hero-photo-wrap {
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
}
.hero-photo {
  position: relative;
  width: 100%;
  max-width: 380px;
  aspect-ratio: 1 / 1.05;
  overflow: hidden;
  border-radius: 2px;
  background: var(--paper-3);
  box-shadow: 0 1px 0 var(--hairline), 0 30px 60px -20px color-mix(in srgb, var(--ink) 25%, transparent);
}
.hero-photo img {
  width: 100%; height: 100%;
  object-fit: cover;
  filter: contrast(1.02) saturate(0.95);
}
/* Hand annotation — "Joe — your tutor". Lives on the empty paper up-left of
   the photo (a sibling of .hero-photo, so .hero-photo's overflow:hidden never
   clips it); the arrow sweeps down-right and its head stops clearly short of
   the photo edge, pointing into the frame. Desktop-only: below 1100px the gap
   between headline and photo disappears, so the annotation goes with it. */
.photo-annotate {
  position: absolute;
  top: -34px;
  /* The photo (max 380px) is centred in the wrap, so its left edge sits at
     50% + 190px from the wrap's right — anchor the annotation just left of it. */
  right: calc(50% + 176px);
  width: 200px;
  /* ink, not rust: annotations speak in one colour sitewide ("the jump.",
     "back on course") and rust stays reserved for its five sanctioned uses */
  color: var(--ink-soft);
  font-family: var(--font-display);
  font-style: italic;
  font-size: 18px;
  line-height: 1.2;
  display: none;
  pointer-events: none;
}
.annotate-text { display: block; white-space: nowrap; }
.annotate-line { width: 120px; height: 100px; display: block; margin: 4px 0 0 34px; }
@media (min-width: 1100px) {
  .photo-annotate { display: block; }
}

.photo-badge {
  position: absolute;
  bottom: 20px;
  left: -28px;
  background: var(--ink);
  color: var(--paper);
  padding: 12px 16px;
  border-radius: 2px;
  box-shadow: 0 20px 40px -10px color-mix(in srgb, var(--ink) 30%, transparent);
  max-width: 220px;
}
.badge-label {
  display: block;
  font-family: var(--font-display);
  font-size: 19px;
  line-height: 1.1;
  font-style: italic;
}
.badge-meta {
  display: block;
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: color-mix(in srgb, var(--paper) 70%, transparent);
  margin-top: 6px;
}

/* ============================================================
   PROOF BAR (4 items)
============================================================ */
.proof-bar {
  border-top: 1px solid var(--hairline);
  border-bottom: 1px solid var(--hairline);
  background: var(--paper-2);
  padding: 28px 0;
  position: relative;
  overflow: hidden;
}
/* Same 4%-opacity grid-paper as the hero / final CTA — carries the whiteboard
   ground through the credentials band. Faded from the right so it reads as a
   continuation of the hero's grid, not a new wallpaper. */
.proof-bar::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: var(--grid-paper-ink);
  background-size: 64px 64px;
  mask-image: linear-gradient(to left, black 0%, black 25%, transparent 75%);
  pointer-events: none;
}
.proof-grid {
  position: relative;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 36px;
}
.proof-item {
  display: flex;
  align-items: flex-start;
  gap: 12px;
}
.proof-num {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.06em;
  color: var(--accent);
  padding-top: 4px;
  font-weight: 500;
}
.proof-label {
  font-family: var(--font-display);
  font-size: 22px;
  line-height: 1.1;
  color: var(--ink);
}
.proof-detail {
  font-size: 12px;
  font-family: var(--font-mono);
  color: var(--muted);
  letter-spacing: 0.02em;
  margin-top: 4px;
}

/* ============================================================
   SHARED SECTION BITS
============================================================ */
.section-eyebrow {
  display: flex;
  align-items: center;
  gap: 12px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 24px;
}
.eyebrow-rule {
  width: 24px;
  height: 1px;
  background: var(--accent);
}
.section-eyebrow-light {
  color: color-mix(in srgb, var(--paper) 70%, transparent);
}
.section-head {
  max-width: 740px;
  margin: 0 auto 56px;
  text-align: center;
}
.section-head .section-eyebrow { justify-content: center; }
.section-head-left { text-align: left; margin: 0 0 56px; max-width: none; }
.section-head-left .section-eyebrow { justify-content: flex-start; }
.section-head-split {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 24px;
  flex-wrap: wrap;
}
.section-title {
  font-family: var(--font-display);
  font-weight: 400;
  font-size: clamp(34px, 4.4vw, 56px);
  line-height: 1.05;
  letter-spacing: -0.02em;
  margin: 0;
  color: var(--ink);
}

/* ============================================================
   WHY EXAMINER (condensed)
============================================================ */
.differ {
  padding: clamp(72px, 10vw, 130px) 0;
}
.differ-inner {
  max-width: 920px;
  margin: 0 auto;
  text-align: center;
}
.differ-inner .section-eyebrow { justify-content: center; }
.pull {
  font-family: var(--font-display);
  font-size: clamp(32px, 4vw, 52px);
  line-height: 1.1;
  letter-spacing: -0.018em;
  color: var(--ink);
  margin: 0 0 40px;
}
.pull em {
  color: var(--accent);
  font-style: italic;
}
.differ-cta {
  display: flex;
  justify-content: center;
}

/* ============================================================
   OFFER (What lessons look like) — preview
============================================================ */
.offer {
  padding: clamp(72px, 10vw, 140px) 0;
  background: var(--paper-2);
  border-top: 1px solid var(--hairline);
  border-bottom: 1px solid var(--hairline);
}
.offer-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0;
  border-top: 1px solid var(--hairline);
  border-bottom: 1px solid var(--hairline);
  background: var(--paper);
}
.offer-card {
  padding: 36px 32px 40px;
  border-right: 1px solid var(--hairline);
  display: flex;
  flex-direction: column;
  gap: 14px;
}
.offer-card:last-child { border-right: 0; }
.offer-card-num {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 500;
}
.offer-card h3 {
  font-family: var(--font-display);
  font-size: 26px;
  line-height: 1.1;
  margin: 0;
  color: var(--ink);
  font-weight: 400;
  letter-spacing: -0.015em;
}
.offer-card p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 15px;
  line-height: 1.6;
}
.offer-cta {
  margin-top: 36px;
  display: flex;
  align-items: center;
  gap: 20px;
  flex-wrap: wrap;
}
.offer-cta-meta {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--muted);
  letter-spacing: 0.02em;
}

/* ============================================================
   TESTIMONIALS CAROUSEL
============================================================ */
.testimonials {
  padding: clamp(80px, 10vw, 140px) 0;
}
.carousel {
  position: relative;
}
.carousel-track {
  display: flex;
  /* Equal card heights (Joe's ruling 2026-08-14): the default stretch keeps
     the row composed; quotes grow so the byline sits on each card's bottom
     rule. Ragged natural heights were tried and looked odd. */
  gap: 24px;
  overflow-x: auto;
  scroll-snap-type: x mandatory;
  scrollbar-width: none;
  -ms-overflow-style: none;
  padding: 8px 4px 24px;
}
.carousel-track::-webkit-scrollbar { display: none; }
.t-card {
  flex: 0 0 calc((100% - 48px) / 3);
  scroll-snap-align: start;
  background: var(--paper);
  border: 1px solid var(--hairline);
  border-radius: 4px;
  padding: 36px 30px 28px;
  display: flex;
  flex-direction: column;
  gap: 18px;
  position: relative;
  min-height: 320px;
  transition: opacity .25s ease, border-color .2s ease, transform .25s ease;
  opacity: 0.75;
  transform: scale(0.985);
}
.t-card.is-active {
  opacity: 1;
  transform: scale(1);
  /* border emphasis only — shadows are reserved for photographs, and the
     resting row reads composed rather than half-loaded */
  border-color: color-mix(in srgb, var(--ink) 30%, var(--hairline));
}
/* Single testimonial (placeholders hidden): center it and let it breathe
   instead of sitting in a one-third-width column with empty space beside it. */
.carousel-track:has(> .t-card:only-child) { justify-content: center; }
.t-card:only-child { flex: 0 0 min(100%, 620px); }
.t-card-placeholder {
  background: repeating-linear-gradient(
    135deg,
    var(--paper) 0 14px,
    color-mix(in srgb, var(--hairline) 40%, var(--paper)) 14px 15px
  );
}
.t-card-placeholder .t-quote { color: var(--muted); font-style: italic; }
.t-card-placeholder .t-author,
.t-card-placeholder .t-context { color: var(--muted); }
.t-mark {
  font-family: var(--font-display);
  font-size: 70px;
  color: var(--accent);
  line-height: 0.4;
  height: 22px;
  opacity: 0.7;
}
.t-quote {
  font-family: var(--font-display);
  font-style: italic;
  font-size: clamp(18px, 1.6vw, 22px);
  line-height: 1.35;
  letter-spacing: -0.005em;
  color: var(--ink);
  margin: 0;
  flex-grow: 1;
}
.t-meta {
  border-top: 1px solid var(--hairline);
  padding-top: 14px;
  display: flex;
  flex-direction: column;
  gap: 3px;
}
.t-author {
  font-weight: 600;
  color: var(--ink);
  font-size: 14.5px;
}
.t-context {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--muted);
}
.carousel-controls {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 18px;
  margin-top: 16px;
}
.carousel-btn {
  width: 44px; height: 44px;
  border-radius: 50%;
  border: 1px solid var(--hairline);
  background: var(--paper);
  color: var(--ink);
  cursor: pointer;
  font-size: 16px;
  font-family: var(--font-body);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  transition: border-color .15s, background .15s, color .15s;
}
.carousel-btn:hover {
  border-color: var(--ink);
  background: var(--ink);
  color: var(--paper);
}
.carousel-dots {
  display: flex;
  gap: 8px;
  align-items: center;
}
.carousel-dot {
  /* 24px+ hit target around an 8px visual dot (drawn by ::before) —
     bare 8px buttons 8px apart guarantee mis-taps. */
  width: 28px; height: 28px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  border: 0;
  background: none;
  padding: 0;
  cursor: pointer;
}
.carousel-dot::before {
  content: "";
  width: 8px; height: 8px;
  border-radius: 50%;
  /* idle dots at var(--muted), not hairline — 1.33:1 failed non-text contrast */
  background: var(--muted);
  transition: background .2s, transform .2s;
}
.carousel-dot:hover::before { background: var(--ink); }
.carousel-dot.is-active::before {
  background: var(--accent);
  transform: scale(1.3);
}

/* ============================================================
   INSIGHTS PREVIEW
============================================================ */
.insights {
  padding: clamp(72px, 10vw, 140px) 0;
  background: var(--paper-2);
  border-top: 1px solid var(--hairline);
  border-bottom: 1px solid var(--hairline);
}
/* Revision notes preview — white block so it alternates with the
   paper-2 Insights section directly below it */
.resource-preview { background: var(--paper); border-bottom: 0; }
.resource-preview-lede {
  max-width: 60ch;
  margin: -32px 0 40px;
  color: var(--ink-soft, #555);
  font-size: clamp(15px, 1.4vw, 17px);
  line-height: 1.6;
}
.insights-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0;
  border-top: 1px solid var(--hairline);
  background: var(--paper);
}
.insight-card {
  display: flex;
  flex-direction: column;
  gap: 14px;
  padding: 32px 30px 36px;
  text-decoration: none;
  color: inherit;
  border-right: 1px solid var(--hairline);
  border-bottom: 1px solid var(--hairline);
  transition: background .15s ease;
  position: relative;
}
.insight-card:last-child { border-right: 0; }
.insight-card:hover { background: var(--paper-2); }
.insight-card:hover .insight-read { color: var(--accent); }
.insight-num {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 500;
}
.insight-meta {
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--muted);
}
.insight-title {
  font-family: var(--font-display);
  font-size: 24px;
  line-height: 1.15;
  letter-spacing: -0.012em;
  margin: 0;
  color: var(--ink);
  font-weight: 400;
}
.insight-excerpt {
  margin: 0;
  font-size: 14.5px;
  line-height: 1.55;
  color: var(--ink-soft);
  flex-grow: 1;
}
.insight-read {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--ink-soft);
  margin-top: auto;
  transition: color .15s;
}

/* ============================================================
   FAQ
============================================================ */
.faq { padding: clamp(72px, 10vw, 140px) 0; }
/* When the FAQ sits directly below the testimonials (e.g. tuition page),
   collapse the doubled section padding so the gap matches the normal rhythm. */
.testimonials + .faq { padding-top: clamp(24px, 3vw, 40px); }
.faq-inner { max-width: var(--maxw); margin: 0 auto; }
.faq-list { max-width: 680px; border-top: 1px solid var(--hairline); }
/* Wide viewports: eyebrow + title become a sticky left column with the
   (widened) question list on the right, so a long FAQ doesn't strand the
   right half of the page. Keyed off the shared .faq-inner > .section-head +
   .faq-list structure, so any page using it (e.g. tuition) picks it up. */
@media (min-width: 1100px) {
  .faq-inner {
    display: grid;
    grid-template-columns: minmax(0, 1fr) minmax(680px, 800px);
    gap: clamp(48px, 6vw, 88px);
    align-items: start;
  }
  .faq-inner .section-head-left {
    margin: 0;
    position: sticky;
    top: 110px;
  }
  .faq-list { max-width: 800px; }
}
.faq-item { border-bottom: 1px solid var(--hairline); }
.faq-item summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 24px 0;
  cursor: pointer;
  list-style: none;
  font-family: var(--font-display);
  font-size: clamp(20px, 2vw, 26px);
  letter-spacing: -0.01em;
  color: var(--ink);
  transition: color .15s;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary:hover { color: var(--accent); }
.faq-indicator {
  width: 28px; height: 28px;
  border: 1px solid var(--hairline);
  border-radius: 50%;
  position: relative;
  flex-shrink: 0;
  transition: border-color .15s, background .15s;
}
.faq-indicator::before,
.faq-indicator::after {
  content: "";
  position: absolute;
  background: var(--ink);
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  transition: opacity .2s ease, transform .2s ease;
}
.faq-indicator::before { width: 10px; height: 1px; }
.faq-indicator::after  { width: 1px; height: 10px; }
.faq-item[open] .faq-indicator { background: var(--accent); border-color: var(--accent); }
.faq-item[open] .faq-indicator::before,
.faq-item[open] .faq-indicator::after { background: var(--paper); }
.faq-item[open] .faq-indicator::after { transform: translate(-50%, -50%) scaleY(0); }
.faq-body {
  padding: 0 0 24px;
  max-width: 70ch;
}
.faq-body p {
  margin: 0;
  color: var(--ink-soft);
  font-size: 16px;
  line-height: 1.6;
}
.faq-body a {
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-thickness: 1px;
}

/* ============================================================
   FINAL CTA
============================================================ */
.final-cta {
  background: var(--dark);
  color: var(--paper);
  padding: clamp(72px, 10vw, 130px) 0;
  position: relative;
  overflow: hidden;
}
.final-cta::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: var(--grid-paper-light);
  background-size: 64px 64px;
  mask-image: radial-gradient(ellipse at bottom left, black 0%, black 30%, transparent 75%);
  pointer-events: none;
}
.final-cta-inner {
  position: relative;
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: clamp(40px, 6vw, 80px);
  align-items: end;
}
.final-cta-title {
  font-family: var(--font-display);
  font-weight: 400;
  font-size: clamp(40px, 5.5vw, 76px);
  line-height: 1;
  letter-spacing: -0.025em;
  margin: 0 0 28px;
  color: var(--paper);
}
.final-cta-title .accent-light {
  color: var(--accent-soft);
  font-style: italic;
}
.final-cta-lede {
  font-size: 17px;
  line-height: 1.55;
  color: color-mix(in srgb, var(--paper) 75%, transparent);
  max-width: 50ch;
  margin: 0;
}
.final-cta-actions {
  display: flex;
  flex-direction: column;
  gap: 12px;
  align-items: flex-start;
}
.reply-note {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.04em;
  color: color-mix(in srgb, var(--paper) 50%, transparent);
  margin: 8px 0 0;
}

/* ============================================================
   FOOTER
============================================================ */
.footer {
  background: var(--paper);
  padding: 56px 0 28px;
  border-top: 1px solid var(--hairline);
}
.footer-grid {
  display: grid;
  grid-template-columns: 1.4fr 1fr;
  gap: 40px;
  padding-bottom: 40px;
  border-bottom: 1px solid var(--hairline);
}
.footer-blurb {
  font-size: 14.5px;
  color: var(--muted);
  max-width: 36ch;
  margin: 16px 0 0;
  line-height: 1.55;
}
.footer-cols {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}
.footer-cols h5,
.footer-cols .footer-col-title {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  font-weight: 500;
  margin: 0 0 16px;
}
.footer-cols a,
.footer-cols span.footer-meta {
  display: block;
  font-size: 14px;
  color: var(--ink-soft);
  text-decoration: none;
  padding: 4px 0;
  transition: color .15s;
}
.footer-cols a:hover { color: var(--accent); }
.footer-meta {
  font-family: var(--font-mono);
  font-size: 11.5px !important;
  color: var(--muted) !important;
  margin-top: 8px;
  letter-spacing: 0.02em;
}
.footer-bottom {
  display: flex;
  justify-content: space-between;
  margin-top: 24px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  color: var(--muted);
  letter-spacing: 0.02em;
}

/* ============================================================
   RESPONSIVE
============================================================ */
@media (max-width: 1100px) {
  .proof-grid { grid-template-columns: repeat(2, 1fr); gap: 24px 36px; }
  .t-card { flex: 0 0 calc((100% - 24px) / 2); }
}
@media (max-width: 980px) {
  .hero-grid { grid-template-columns: 1fr; gap: 48px; }
  .hero-photo-wrap { order: -1; max-width: 320px; margin: 0 auto; }
  .proof-grid { grid-template-columns: repeat(2, 1fr); gap: 24px; }
  .offer-grid { grid-template-columns: 1fr; }
  .offer-card { border-right: 0; border-bottom: 1px solid var(--hairline); }
  .offer-card:last-child { border-bottom: 0; }
  .insights-grid { grid-template-columns: 1fr; }
  .insight-card { border-right: 0; }
  .t-card { flex: 0 0 100%; min-height: 260px; }
  .final-cta-inner { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
  .nav { gap: 16px; }
  .nav a:not(.nav-cta) { display: none; }
  .section-head-split { flex-direction: column; align-items: flex-start; }
}
@media (max-width: 600px) {
  .nav { gap: 10px; }
  .brand-sub { display: none; }
  .footer-cols { grid-template-columns: 1fr 1fr; }
  .footer-bottom { flex-direction: column; gap: 6px; }
  /* Keep the examiner badge's overhang inside the viewport — at -28px it sat
     flush against (and 1px clipped by) the screen edge. */
  .photo-badge { left: -12px; }
}

/* ============================================================
   MOBILE NAV DRAWER
============================================================ */
.menu-toggle {
  display: none;
  align-items: center;
  gap: 6px;
  background: none;
  border: 1px solid var(--hairline);
  border-radius: 999px;
  padding: 9px 16px;
  cursor: pointer;
  font-size: 13.5px;
  font-weight: 500;
  font-family: var(--font-body);
  color: var(--ink);
  line-height: 1;
  transition: border-color .15s, background .15s;
  white-space: nowrap;
}
.menu-toggle:hover { border-color: var(--ink); }
@media (max-width: 980px) {
  /* Collapsed-nav header: a circular 3-line "hamburger" toggle paired with a
     larger Enquire pill of matching height. The toggle goes icon-only — the
     "Menu" label is hidden with font-size:0 (the aria-label keeps it
     accessible), and three currentColor bars are drawn with a ::before plus
     two box-shadow copies, rounded to match the brand mark's stroke caps.
     The brand takes the slack (margin-right:auto) so the Enquire pill and
     toggle stay grouped together on the far right instead of space-between
     stranding Enquire in the middle on wide (iPad) viewports. */
  .brand { margin-right: auto; }
  .menu-toggle {
    display: inline-flex;
    justify-content: center;
    flex-shrink: 0;
    width: 46px;
    height: 46px;
    padding: 0;
    gap: 0;
    margin-left: 12px;
    font-size: 0;
    border-radius: 999px;
  }
  .menu-toggle::before {
    content: "";
    width: 20px;
    height: 2px;
    border-radius: 2px;
    background: currentColor;
    box-shadow: 0 -6px 0 currentColor, 0 6px 0 currentColor;
  }
  .nav a.nav-cta {
    display: inline-flex;
    align-items: center;
    min-height: 46px;
    padding: 0 22px;
    font-size: 15px;
    line-height: 1;
  }
}

/* Full-screen overlay behind the drawer */
.drawer-overlay {
  position: fixed;
  inset: 0;
  background: color-mix(in srgb, var(--ink) 45%, transparent);
  z-index: 1999;
  opacity: 0;
  pointer-events: none;
  transition: opacity .28s ease;
}
.drawer-overlay.is-open {
  opacity: 1;
  pointer-events: auto;
}

/* Slide-in panel */
.mobile-drawer {
  position: fixed;
  top: 0; right: 0;
  width: min(340px, 90vw);
  height: 100dvh;
  background: var(--paper);
  border-left: 1px solid var(--hairline);
  z-index: 2000;
  display: flex;
  flex-direction: column;
  transform: translateX(100%);
  visibility: hidden;            /* keep the off-screen drawer out of the tab order / a11y tree when closed */
  transition: transform .28s cubic-bezier(.4, 0, .2, 1), visibility 0s linear .28s;
  box-shadow: -24px 0 56px -16px color-mix(in srgb, var(--ink) 14%, transparent);
  overflow-y: auto;
}
.mobile-drawer.is-open {
  transform: translateX(0);
  visibility: visible;
  transition: transform .28s cubic-bezier(.4, 0, .2, 1), visibility 0s;
}

.drawer-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 24px;
  border-bottom: 1px solid var(--hairline);
  flex-shrink: 0;
}
.drawer-brand {
  font-family: var(--font-display);
  font-size: 18px;
  color: var(--ink);
  letter-spacing: -0.01em;
}
.drawer-close {
  background: none;
  border: 1px solid var(--hairline);
  border-radius: 50%;
  width: 36px; height: 36px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 17px;
  line-height: 1;
  color: var(--ink);
  transition: border-color .15s, background .15s;
}
.drawer-close:hover { border-color: var(--ink); background: var(--paper-2); }

.mobile-drawer nav {
  display: flex;
  flex-direction: column;
  padding: 20px 24px 32px;
  gap: 0;
  flex-grow: 1;
}
.mobile-drawer nav a {
  font-family: var(--font-display);
  font-size: 30px;
  line-height: 1.2;
  letter-spacing: -0.018em;
  color: var(--ink);
  text-decoration: none;
  padding: 14px 0;
  border-bottom: 1px solid var(--hairline);
  transition: color .15s;
}
.mobile-drawer nav a:last-of-type { border-bottom: 0; }
.mobile-drawer nav a:hover { color: var(--accent); }
.mobile-drawer nav a.drawer-cta {
  margin-top: 24px;
  border: none;
  background: var(--ink);
  color: var(--paper) !important;
  padding: 14px 22px;
  border-radius: 999px;
  font-family: var(--font-body);
  font-size: 15px;
  font-weight: 500;
  text-align: center;
  display: block;
  transition: background .15s;
}
.mobile-drawer nav a.drawer-cta:hover { background: var(--accent); }

/* ============================================================
   STICKY BOTTOM CTA
============================================================ */
.sticky-cta {
  position: fixed;
  bottom: 0; left: 0; right: 0;
  z-index: 900;
  background: var(--dark);
  padding: 12px clamp(16px, 3vw, 32px);
  padding-bottom: calc(12px + env(safe-area-inset-bottom, 0px));
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 18px;
  transform: translateY(100%);
  transition: transform .32s cubic-bezier(.4, 0, .2, 1);
  border-top: 1px solid color-mix(in srgb, var(--paper) 10%, transparent);
}
.sticky-cta.is-visible { transform: translateY(0); }
.sticky-cta-text {
  font-size: 14.5px;
  font-weight: 500;
  color: color-mix(in srgb, var(--paper) 75%, transparent);
}
.sticky-cta-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  background: var(--ink); /* R3 item 3: the header's ink pill */
  color: var(--paper);
  padding: 9px 20px;
  border-radius: 999px;
  font-size: 14px;
  font-weight: 500;
  text-decoration: none;
  white-space: nowrap;
  transition: background .15s;
}
.sticky-cta-btn:hover { background: var(--accent); }
/* Reserve space so the fixed CTA bar never sits over the footer / last
   content — the bar appears at EVERY width once scrolled, so the reservation
   can't live only in the mobile media query. Scoped to pages that have the
   bar via :has(); the unconditional mobile rule below is the fallback for
   engines without :has() support (restoring the pre-existing behaviour). */
/* R3 item 37: notes pages hide the bar (site.js sets hidden), so they reserve nothing. */
body:has(.sticky-cta:not([hidden])) { padding-bottom: calc(64px + env(safe-area-inset-bottom, 0px)); }
@media (max-width: 600px) {
  .sticky-cta-text { display: none; }
  .sticky-cta { padding: 10px 16px calc(10px + env(safe-area-inset-bottom, 0px)); }
  .sticky-cta-btn { flex-grow: 1; justify-content: center; font-size: 15px; }
}
@supports not selector(:has(a)) {
  @media (max-width: 600px) { body { padding-bottom: calc(64px + env(safe-area-inset-bottom, 0px)); } }
}

/* ============================================================
   FOCUS VISIBILITY — a branded ring for keyboard users on every
   interactive element (the revision widgets already have one).
============================================================ */
a:focus-visible,
button:focus-visible,
summary:focus-visible,
[tabindex]:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: 2px;
}
/* On dark grounds the oxide ring vanishes — use paper instead. */
.final-cta a:focus-visible,
.sticky-cta a:focus-visible {
  outline-color: var(--paper);
}
/* Anchor jumps land below the sticky header instead of underneath it. */
[id] {
  scroll-margin-top: 90px;
}

/* ============================================================
   REDUCED MOTION — honour the user's OS "reduce motion" setting
   (carousel autoplay is additionally disabled in carousel.js)
============================================================ */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
    scroll-behavior: auto !important;
  }
}

/* ============================================================
   SITE CHROME — the one copy of the header, drawer, footer and topic-search rules
   (J5, 2026-10-08). Moved here whole from page.css so /practice/, which loads
   styles.css and never page.css, draws the same header from the same rules.
============================================================ */
/* ==== i2-chrome: shared navigation, drawer, footer and topic search ==== */
.site-chrome { color-scheme: light; }
.header.site-chrome { position: sticky; top: 0; z-index: 1000; background: var(--paper); } /* sticky as the live site's header always was: the header button is the one-tap tuition route (lead, 2026-10-08) */
.site-chrome .header-inner { gap: 16px; padding-block: 12px; }
.site-chrome .brand { flex-shrink: 0; min-height: 44px; }
.site-nav { display: flex; align-items: center; gap: 10px; }
.site-nav a, .site-nav button, .site-phone-controls a, .site-phone-controls button,
.site-chrome .drawer-close, .site-search button, .site-chrome summary {
  display: inline-flex; align-items: center; justify-content: center; min-height: 44px;
  padding: 8px; color: var(--ink); font: 500 14px/1.4 var(--font-body); text-decoration: none;
}
.site-nav a { white-space: nowrap; }
.site-nav [aria-current="page"] { text-decoration: underline; text-underline-offset: 5px; }
.site-level { display: flex; position: relative; align-items: center; }
/* R3 item 22: a quiet chevron beside its label; the 44 px tap height stays through the shared min-height. */
.site-nav .site-disclosure { min-width: 28px; width: 28px; border: 0; border-radius: 4px; padding: 8px 2px; margin-left: -6px; color: var(--muted); background: transparent; cursor: pointer; }
.site-nav [hidden], .site-phone-controls [hidden] { display: none; }
.site-nav .nav-cta { padding-inline: 16px; }
.site-search-icon { display: none; flex-shrink: 0; }
.site-level-menu { position: absolute; inset: calc(100% + 8px) auto auto 0; width: min(520px, 80vw); max-height: calc(100vh - 88px); /* to 24 px above the screen's foot (panel top is 64) */ overflow-y: auto; padding: 16px; background: var(--paper); border: 1px solid var(--hairline); border-radius: 12px; box-shadow: 0 12px 36px #0002; }
.site-level-menu a { display: block; white-space: normal; min-height: 44px; padding: 10px; border-bottom: 1px solid var(--hairline); }
.site-level-menu > a:last-child { border-bottom: 0; }
/* J9: the all-levels index (the live nav called it "Revision"), quiet, at the foot of both menus. */
.site-level-menu > .site-menu-all { min-height: 44px; padding: 10px; font-size: 13px; color: var(--muted); grid-column: 1 / -1; }
/* R3 items 6-7: the AQA heading link opens each group; the A-Level panel is two columns by task. */
.site-menu-head { font-weight: 600; border-bottom: 2px solid var(--ink) !important; margin-bottom: 8px; }
.site-level-menu--alevel { width: min(640px, 90vw); display: grid; grid-template-columns: 1fr 1fr; column-gap: 16px; left: 50%; transform: translateX(-50%); } /* centred on its label: hung from the label's left it ran 188 px off a 981 px screen */
.site-level-menu--alevel > .site-menu-feature, .site-level-menu--alevel > .site-menu-pricing, .site-level-menu--alevel > .site-menu-tuition { grid-column: 1 / -1; }
.site-level-menu--alevel > .site-menu-feature { margin-top: 12px; }
/* The GCSE panel fits a 700 px-tall screen: wide enough for one-line chapter titles, centred on its label,
   and the four rows under the chapters two to a line, so "GCSE tuition with Joe" is never cut off. */
#site-gcse-menu { width: min(720px, 90vw); left: 50%; transform: translateX(-50%); }
#site-gcse-menu:not([hidden]) { display: grid; grid-template-columns: 1fr 1fr; column-gap: 16px; } /* the id outranks .site-nav [hidden], so the grid applies only while open */
#site-gcse-menu > .site-menu-head, #site-gcse-menu > .site-chapters, #site-gcse-menu > .site-menu-tuition { grid-column: 1 / -1; }
#site-gcse-menu > .site-chapters { column-gap: 16px; } /* both columns start where the rows below start */
.site-chrome small { display: block; font: 400 13px/1.5 var(--font-body); color: var(--muted); }
.site-chrome .rn-chem, .site-search .rn-chem { text-transform: none; letter-spacing: normal; }
.site-menu-feature { background: var(--ink); color: var(--paper) !important; border-radius: 8px; }
.site-menu-feature small { color: var(--paper); }
.site-menu-tuition { border-top: 2px solid var(--accent); }
.site-chapters { display: grid; grid-template-columns: 1fr 1fr; gap: 4px; }
.site-chapters a { font-size: 13px; }
.site-phone-controls { display: none; align-items: center; gap: 4px; }
.site-phone-controls .site-phone-action { white-space: normal; text-align: center; }
.site-phone-controls .site-phone-search { width: 44px; min-width: 44px; padding: 0; }
.site-phone-controls .site-search-icon { display: block; }
.site-phone-controls .menu-toggle { width: 44px; min-width: 44px; height: 44px; padding: 0; margin-left: 0; }
.site-chrome .menu-toggle::before { display: none; }
.mobile-drawer.site-chrome { width: min(420px, 100vw); }
.site-chrome .drawer-close { width: 44px; height: 44px; flex-shrink: 0; }
.site-chrome.mobile-drawer nav { padding: 12px 20px 32px; }
.site-chrome.mobile-drawer nav a { display: block; font: 500 16px/1.5 var(--font-body); letter-spacing: normal; min-height: 44px; padding: 12px 8px; }
.site-drawer-signin { text-decoration: none !important; }
/* R3 item 8: Close never scrolls away; nested links read as a group; search looks like a field. */
.site-chrome .drawer-header { position: sticky; top: 0; z-index: 1; background: var(--paper); }
.site-chrome.mobile-drawer details a { padding-left: 20px; font-size: 15px; font-weight: 400; }
.site-chrome.mobile-drawer details a.site-menu-head { padding-left: 8px; font-weight: 600; }
.site-chrome.mobile-drawer .site-drawer-search { border: 1px solid var(--ink-soft); border-radius: 999px; padding-inline: 16px; color: var(--muted); }
.site-drawer-doors { display: grid; gap: 8px; margin-block: 12px; }
.site-drawer-doors a { border: 1px solid var(--hairline) !important; border-radius: 8px; }
.site-chrome.mobile-drawer h2 { font: 500 14px/1.5 var(--font-body); margin: 12px 8px 4px; }
.site-chrome.mobile-drawer details { border-top: 1px solid var(--hairline); }
.site-chrome.mobile-drawer summary { display: flex; justify-content: space-between; min-height: 44px; padding: 12px 8px; font-size: 16px; list-style: none; cursor: pointer; }
.site-chrome.mobile-drawer summary::marker { content: ""; }
.site-chrome.mobile-drawer summary::-webkit-details-marker { display: none; }
.site-chrome.mobile-drawer summary::after { content: ""; width: 8px; height: 8px; margin-inline: 12px 4px; flex-shrink: 0; border-right: 2px solid currentColor; border-bottom: 2px solid currentColor; transform: rotate(45deg); }
.site-chrome.mobile-drawer details[open] > summary::after { transform: rotate(225deg); }
.site-chrome .footer-grid { grid-template-columns: 1fr; gap: 28px; }
@media (min-width: 981px) { .site-chrome .footer-grid { grid-template-columns: minmax(240px, 300px) minmax(0, 1fr); gap: 56px; } } /* R3 item 25 */
.site-chrome .footer-cols { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.site-chrome .footer-cols a { min-height: 44px; display: flex; align-items: center; }
.site-footer-brand > a { display: inline-flex; align-items: center; min-height: 44px; color: var(--ink-soft); font-size: 14px; }
.site-coming { font-size: 14px; line-height: 1.6; margin-top: 24px; }
.site-search { color-scheme: light; width: min(720px, calc(100vw - 24px)); max-height: calc(100dvh - 24px); overflow-y: auto; border: 1px solid var(--hairline); border-radius: 12px; background: var(--paper); color: var(--ink); padding: 20px; }
.site-search::backdrop { background: #0007; }
.site-search-top { display: flex; justify-content: space-between; align-items: center; gap: 12px; }
.site-search-top h2 { font: 400 28px/1.2 var(--font-display); margin: 0; text-transform: none; letter-spacing: normal; }
.site-search button { min-width: 44px; border: 1px solid var(--hairline); border-radius: 50%; background: transparent; cursor: pointer; }
.site-search label { display: block; font-size: 15px; margin-block: 16px 8px; }
.site-search input { box-sizing: border-box; width: 100%; min-height: 48px; border: 1px solid var(--ink-soft); border-radius: 6px; padding: 10px; background: var(--paper); color: var(--ink); font: 16px var(--font-body); }
.site-search h3 { font: 500 14px/1.5 var(--font-body); margin-block: 20px 4px; text-transform: none; letter-spacing: normal; }
.site-search-results-link { display: block; min-height: 44px; padding: 10px 8px; color: var(--ink); text-decoration: none; border-bottom: 1px solid var(--hairline); }
.site-search-results-link small { display: block; color: var(--muted); }
.site-search-hubs a { display: inline-flex; align-items: center; min-height: 44px; color: var(--accent); }
/* Only the results scroll: the heading, Close, the field and the status line stay in view, so a
   student refining "titration" on a phone never scrolls back up to type (design round 3, S4). */
.site-search[open] { display: flex; flex-direction: column; overflow: hidden; }
.site-search[open] > * { flex-shrink: 0; }
.site-search #site-search-results { flex-shrink: 1; min-height: 0; overflow-y: auto; overscroll-behavior: contain; }
.site-search .site-search-results-link:focus-visible { outline-offset: -3px; } /* inside the scroller, so the ring is not clipped */
/* No-results line: "Did you mean" on its own line, then the three hub links (design round 3, items 26 and 27). */
.site-search [data-search-status] a { display: inline-flex; align-items: center; min-height: 44px; color: var(--accent); }
.site-search-suggest { display: block; }
.site-search-browse { display: flex; flex-wrap: wrap; align-items: center; column-gap: 6px; }
.site-search .site-search-suggest button { display: inline-block; min-width: 0; min-height: 44px; padding: 0; border: 0; border-radius: 0; color: var(--accent); font: inherit; font-weight: 600; text-decoration: underline; text-underline-offset: 3px; }
.site-chrome a:focus-visible, .site-chrome button:focus-visible, .site-chrome summary:focus-visible,
.site-search :focus-visible { outline: 3px solid var(--accent); outline-offset: 3px; }
/* R3 item 10: on wide desktops the search opener looks like the field it opens. */
@media (min-width: 1200px) {
  .site-nav .site-search-open { min-width: 220px; justify-content: flex-start; gap: 8px; padding: 8px 14px;
    border: 1px solid var(--hairline); border-radius: 999px; background: #fff; color: var(--muted); font-weight: 400; }
  .site-nav .site-search-open .site-search-icon { display: block; width: 16px; height: 16px; }
}
/* Compact desktop keeps every primary route visible, including Sign in. */
@media (min-width: 981px) and (max-width: 1199px) {
  .header.site-chrome .header-inner { padding-inline: 16px; gap: 12px; }
  .site-chrome .site-nav { gap: 4px; flex-shrink: 0; }
  .site-nav .site-search-open { width: 44px; min-width: 44px; padding: 0; }
  .site-nav .site-search-text { display: none; }
  .site-nav .site-search-icon { display: block; }
}
@media (max-width: 980px) {
  .site-chrome-ready .site-nav { display: none; }
  .header.site-chrome:not(.site-chrome-ready) .header-inner { flex-wrap: wrap; }
  .header.site-chrome:not(.site-chrome-ready) .site-nav { flex-wrap: wrap; }
  .site-phone-controls { display: flex; }
  .site-chrome .menu-toggle:not([hidden]) { display: inline-flex; border: 1px solid var(--hairline); border-radius: 6px; background: transparent; }
  /* The phone menu button is an icon beside the search magnifier (Joe, launch night 14 Oct): no frame, like the magnifier,
     so the two read as a pair; the border stays transparent so the 44 px target does not move. */
  .site-phone-controls .menu-toggle:not([hidden]) { border-color: transparent; }
}
@media (max-width: 600px) {
  .header.site-chrome .header-inner { gap: 4px; padding-inline: 8px; }
  .header.site-chrome .brand { gap: 4px; }
  .header.site-chrome .brand-mark { display: inline-flex; width: 28px; height: 28px; flex-shrink: 0; }
  .header.site-chrome .brand-mark svg { width: 28px; height: 28px; }
  .header.site-chrome .brand-name { width: 92px; font-size: 18px; line-height: 1; white-space: normal; }
  .site-phone-controls { flex-shrink: 0; gap: 2px; }
  .site-phone-controls .site-phone-action { width: auto; min-width: 76px; min-height: 44px; padding: 4px 10px; font-size: 13px; line-height: 1.2; } /* R3 item 23: 13 px floor; 10 px sides so the one-line label fits 360 px with room, by the source budget as well as in the browser */
  .site-phone-controls .menu-toggle { font-size: 13px; line-height: 1.2; }
  .site-chrome .footer-cols { grid-template-columns: 1fr 1fr; gap: 20px; }
  .site-chrome .footer-bottom { flex-direction: column; gap: 12px; }
  .site-chapters { grid-template-columns: 1fr; }
}
@media (max-width: 399px) {
  .header.site-chrome .brand-sub { display: none; }
}
/* R3 item 2: on the narrowest phones the header button wraps to two lines rather than pushing Menu off the screen. The cap
   started at 374 px when 360 measured 0.16 px over; the header has since gained width, so 360 px phones (the commonest
   Android width) keep a one-line button and only 359 px and below wrap (reviewer, measured 2026-10-09). */
@media (max-width: 359px) {
  .site-phone-controls .site-phone-action { max-width: 80px; padding-inline: 8px; }
}
@media print { .site-search, .site-phone-controls, .mobile-drawer.site-chrome { display: none !important; } }
/* ---- J5: the /practice/ variant of this header ---------------------------------------------
   The same bar, built from the same template parts (_templates/site-chrome.html). The right-hand
   side differs: the Learn · Practice switch, then the account corner, where the site has Sign in
   and its button. None of these classes appears on a site page. */
/* /practice/'s body text is 16px; the site's is 17px with line-height 1.55, and the header's
   inherited sizes must be the site's so nothing in the bar shifts by a pixel between the two. */
.header.site-chrome--platform, .mobile-drawer.site-chrome--platform { font-size: 17px; line-height: 1.55; }
.site-switch { display: inline-flex; align-items: center; border-radius: 999px; box-shadow: inset 0 0 0 1px var(--hairline); }
.site-nav .site-switch a, .site-phone-controls .site-switch a { padding-inline: 14px; border-radius: 999px; }
.site-switch a[aria-current] { background: var(--ink); color: var(--paper); text-decoration: none; }
.site-account { display: inline-flex; align-items: center; }
.site-nav .site-account-toggle { border: 0; background: transparent; cursor: pointer; }
.site-account-chevron { margin-left: 6px; font-size: 12px; color: var(--muted); }
.site-level-menu.site-account-panel { inset: calc(100% + 8px) 0 auto auto; width: min(280px, 90vw); }
.site-account-who { display: block; padding: 10px; font-size: 13px; color: var(--muted); overflow-wrap: anywhere; border-bottom: 1px solid var(--hairline); }
.site-nav .site-account-panel button { width: 100%; justify-content: flex-start; padding: 10px; border: 0; background: transparent; cursor: pointer; }
.site-drawer-account { display: grid; }
.site-chrome.mobile-drawer .site-drawer-signout { display: block; width: 100%; min-height: 44px; padding: 12px 8px; border: 0; background: transparent; color: var(--ink); font: 500 16px/1.5 var(--font-body); text-align: left; cursor: pointer; }
@media (max-width: 600px) {
  .site-phone-controls .site-switch a { padding-inline: 10px; font-size: 13px; }
}
@media (max-width: 374px) {
  /* Under 375 px the search button gives way so the switch and Menu fit; search is first in the menu. */
  .site-chrome--platform .site-phone-controls .site-phone-search { display: none; }
}
/* ==== end i2-chrome ==== */