/* ============================================================
   Open Run — design system
   Instrument panel meets editorial. Mobile-first; scales to 4K.
   ============================================================ */

/* ---------- tokens ---------- */
:root {
  --font-display: "Iowan Old Style", Charter, "Source Serif 4", Georgia, serif;
  --font-body: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: "SF Mono", "JetBrains Mono", "Cascadia Code", Menlo, Consolas, monospace;

  --r-s: 10px;
  --r-m: 14px;
  --r-l: 20px;
  --r-xl: 28px;

  --topbar-h: 58px;
  --ease: cubic-bezier(.2, 0, 0, 1);
  --t-fast: 150ms;
  --t-med: 220ms;

  --pro: #FF7A2F;
  --flash: #59B7FF;

  font-size: clamp(16px, 14.6px + 0.18vw, 20px); /* grows gently toward 4K */
}

[data-theme="dark"] {
  --bg: #0A0D13;
  --bg-soft: #0D1119;
  --surface: #121826;
  --surface-2: #1A2233;
  --surface-3: #222C42;
  --line: rgba(244, 241, 236, .09);
  --line-strong: rgba(244, 241, 236, .18);
  --text: #F4F1EC;
  --muted: #A2ABBA;
  --dim: #8A93A1;
  --accent: #FF7A2F;
  --accent-soft: rgba(255, 122, 47, .14);
  --accent-ink: #170A02;
  --good: #3ECFA0;
  --good-soft: rgba(62, 207, 160, .13);
  --bad: #FF6B6B;
  --bad-soft: rgba(255, 107, 107, .12);
  --warn: #FFC24B;
  --warn-soft: rgba(255, 194, 75, .12);
  --flash-soft: rgba(89, 183, 255, .14);
  --shadow-1: 0 1px 2px rgba(0, 0, 0, .35);
  --shadow-2: 0 10px 30px rgba(0, 0, 0, .38);
  --shadow-3: 0 24px 70px rgba(0, 0, 0, .5);
  --glow: radial-gradient(1200px 700px at 85% -10%, rgba(255, 122, 47, .13), transparent 60%),
          radial-gradient(1000px 620px at -10% 20%, rgba(89, 183, 255, .1), transparent 55%);
  color-scheme: dark;
}

[data-theme="light"] {
  --bg: #FAF7F2;
  --bg-soft: #F5F1EA;
  --surface: #FFFFFF;
  --surface-2: #F2EEE7;
  --surface-3: #E9E4DA;
  --line: rgba(21, 26, 34, .1);
  --line-strong: rgba(21, 26, 34, .2);
  --text: #151A22;
  --muted: #57606E;
  --dim: #5A6675;
  --accent: #C2410C;
  --accent-soft: rgba(232, 95, 12, .1);
  --accent-ink: #FFF7F1;
  --good: #0E9F6E;
  --good-soft: rgba(14, 159, 110, .1);
  --bad: #D63636;
  --bad-soft: rgba(214, 54, 54, .09);
  --warn: #A16207;
  --warn-soft: rgba(161, 98, 7, .1);
  --flash-soft: rgba(20, 121, 201, .1);
  --pro: #E85F0C;
  --flash: #1479C9;
  --shadow-1: 0 1px 2px rgba(21, 26, 34, .06);
  --shadow-2: 0 10px 30px rgba(21, 26, 34, .09);
  --shadow-3: 0 24px 70px rgba(21, 26, 34, .14);
  --glow: radial-gradient(1200px 700px at 85% -10%, rgba(232, 95, 12, .07), transparent 60%),
          radial-gradient(1000px 620px at -10% 20%, rgba(20, 121, 201, .06), transparent 55%);
  color-scheme: light;
}

/* ---------- reset-ish ---------- */
*, *::before, *::after { box-sizing: border-box; }
[hidden] { display: none !important; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font-body);
  font-size: 1.0625rem;
  line-height: 1.72;
  color: var(--text);
  background: var(--bg);
  background-image: var(--glow);
  background-attachment: fixed;
  min-height: 100dvh;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}
img, svg { display: block; max-width: 100%; }
button { font: inherit; color: inherit; background: none; border: 0; cursor: pointer; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }
p a, li a, td a, .foot-links a { text-decoration: underline; text-underline-offset: 2px; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 6px; }
::selection { background: var(--accent-soft); }

.skip-link {
  position: absolute; left: 12px; top: -60px; z-index: 300;
  background: var(--accent); color: var(--accent-ink);
  padding: 10px 16px; border-radius: var(--r-s); font-weight: 600;
  transition: top var(--t-fast) var(--ease);
}
.skip-link:focus { top: 12px; }

.eyebrow {
  font-family: var(--font-mono);
  font-size: .72rem;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--dim);
}

/* ---------- topbar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 120;
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  background: color-mix(in srgb, var(--bg) 72%, transparent);
  border-bottom: 1px solid var(--line);
  padding-top: env(safe-area-inset-top);
}
.topbar-inner {
  display: flex; align-items: center; gap: 12px;
  height: var(--topbar-h);
  max-width: 1560px; margin: 0 auto;
  padding: 0 14px;
}
.brand { display: flex; align-items: center; gap: 10px; color: var(--text); text-decoration: none; min-width: 0; }
.brand:hover { text-decoration: none; }
.brand-mark {
  width: 34px; height: 34px; border-radius: 10px; flex: none;
  display: grid; place-items: center;
  background: linear-gradient(145deg, var(--surface-2), var(--surface));
  border: 1px solid var(--line-strong);
  box-shadow: var(--shadow-1);
}
.brand-mark svg { width: 22px; height: 22px; }
.brand-mark path { stroke: var(--accent); stroke-width: 2.6; fill: none; stroke-linecap: round; stroke-linejoin: round; }
.brand-text {
  font-family: var(--font-display);
  font-size: 1.22rem; font-weight: 700; letter-spacing: -.01em;
  display: flex; flex-direction: column; line-height: 1.05; white-space: nowrap;
}
.brand-sub {
  font-family: var(--font-mono);
  font-size: .6rem; letter-spacing: .08em; text-transform: uppercase;
  color: var(--dim); font-weight: 500; margin-top: 3px;
}
.topbar-right { margin-left: auto; display: flex; align-items: center; gap: 10px; }

.icon-btn {
  width: 40px; height: 40px; border-radius: 12px;
  display: grid; place-items: center;
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--muted);
  transition: border-color var(--t-fast), color var(--t-fast), transform var(--t-fast) var(--ease);
}
.icon-btn:hover { color: var(--text); border-color: var(--line-strong); }
.icon-btn:active { transform: scale(.96); }
.icon-btn svg { width: 20px; height: 20px; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linecap: round; }

.top-progress { display: flex; align-items: center; gap: 8px; }
.top-progress .tp-label { font-family: var(--font-mono); font-size: .72rem; color: var(--dim); }

/* ---------- progress ring ---------- */
.ring { transform: rotate(-90deg); }
.ring .ring-bg { stroke: var(--line-strong); }
.ring .ring-fg { stroke: var(--accent); transition: stroke-dashoffset .6s var(--ease); }

/* ---------- layout ---------- */
.layout {
  position: relative;
  max-width: 1560px; margin: 0 auto;
  display: grid;
  grid-template-columns: minmax(0, 1fr);
}
.main { min-width: 0; padding: 22px 16px 64px; display: grid; justify-items: center; }
.main > * { width: 100%; max-width: 880px; }
.rail { display: none; }

/* ---------- sidebar ---------- */
.sidebar {
  position: fixed; inset: 0 auto 0 0; z-index: 140;
  width: min(84vw, 320px);
  background: var(--bg-soft);
  border-right: 1px solid var(--line);
  padding: calc(env(safe-area-inset-top) + 18px) 16px calc(env(safe-area-inset-bottom) + 18px);
  overflow-y: auto;
  transform: translateX(-102%);
  transition: transform var(--t-med) var(--ease);
  box-shadow: var(--shadow-3);
}
.sidebar.open { transform: translateX(0); }
.sidebar-backdrop {
  position: fixed; inset: 0; z-index: 130;
  background: rgba(4, 6, 10, .55);
  backdrop-filter: blur(2px);
}
.sidebar-head { margin-bottom: 14px; }
.sidebar-title { font-family: var(--font-display); font-size: 1.05rem; font-weight: 700; margin-top: 4px; }
.sidebar-foot { margin-top: 18px; }
.foot-reset {
  display: block; margin: 10px auto 0;
  font-family: var(--font-mono); font-size: .64rem;
  letter-spacing: .1em; text-transform: uppercase; color: var(--dim);
}
.foot-reset:hover { color: var(--bad); }

.lesson-list { list-style: none; margin: 0; padding: 0; display: grid; gap: 4px; }
.lesson-link {
  display: grid; grid-template-columns: 26px 1fr auto; align-items: center; gap: 10px;
  padding: 9px 10px; border-radius: var(--r-m);
  color: var(--muted); text-decoration: none;
  border: 1px solid transparent;
  transition: background var(--t-fast), border-color var(--t-fast), color var(--t-fast);
}
.lesson-link:hover { background: var(--surface); color: var(--text); text-decoration: none; }
.lesson-link.current { background: var(--surface); border-color: var(--line-strong); color: var(--text); }
.lesson-link .num {
  font-family: var(--font-mono); font-size: .72rem; color: var(--dim);
  width: 26px; height: 26px; border-radius: 8px;
  display: grid; place-items: center;
  background: var(--surface-2); border: 1px solid var(--line);
}
.lesson-link.current .num { color: var(--accent-ink); background: var(--accent); border-color: var(--accent); }
.lesson-link .nm { font-size: .9rem; line-height: 1.3; }
.lesson-link .st { display: grid; place-items: center; }

/* ---------- home ---------- */
.home-hero {
  position: relative;
  padding: clamp(26px, 6vw, 72px) 0 clamp(20px, 4vw, 44px);
}
.home-hero h1 {
  font-family: var(--font-display);
  font-size: clamp(2.35rem, 6.4vw, 4.4rem);
  line-height: 1.02; letter-spacing: -.022em;
  margin: .35em 0 .3em; max-width: 16ch;
}
.home-hero h1 .accent { color: var(--accent); }
.home-hero .lede {
  font-size: clamp(1.08rem, 1.6vw, 1.3rem);
  color: var(--muted); max-width: 62ch; line-height: 1.6;
}
.hero-cta { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 26px; }
.hero-note { margin-top: 14px; font-size: .85rem; color: var(--dim); }

.facts-strip {
  display: grid; grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px; margin: 18px 0 8px;
}
.fact {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--r-l); padding: 14px 16px;
  box-shadow: var(--shadow-1);
}
.fact .v { font-family: var(--font-mono); font-size: clamp(1.05rem, 2vw, 1.35rem); font-weight: 600; letter-spacing: -.01em; }
.fact .k { font-size: .78rem; color: var(--dim); margin-top: 2px; }
.fact .pro { color: var(--pro); }
.fact .flash { color: var(--flash); }

/* landing-page sections */
.story-grid { display: grid; gap: 22px; margin-top: 10px; }
.story-text p { max-width: 62ch; margin: 0 0 1em; }
.story-text b { font-weight: 650; }
.story-side .pull { margin-top: 0; font-size: clamp(1.35rem, 2.4vw, 1.8rem); }
.story-foot { font-size: .9rem; color: var(--muted); line-height: 1.6; margin: 0; }
.stats-showcase { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 12px; margin-top: 16px; }
.stat-big {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--r-l); padding: 18px 20px;
  box-shadow: var(--shadow-1);
}
.stat-big .sv {
  font-family: var(--font-display);
  font-size: clamp(1.8rem, 3.2vw, 2.6rem);
  font-weight: 700; letter-spacing: -.02em; line-height: 1.05;
}
.stat-big:nth-child(1) .sv { color: var(--accent); }
.stat-big:nth-child(6) .sv { color: var(--good); }
.stat-big .sk { margin-top: 6px; font-weight: 620; font-size: .95rem; }
.stat-big .sn { margin-top: 4px; font-size: .8rem; color: var(--dim); line-height: 1.5; }
.cta-band {
  position: relative; overflow: hidden;
  margin: 48px 0 8px; padding: 38px 28px;
  border-radius: var(--r-xl);
  background:
    linear-gradient(var(--surface), var(--surface)) padding-box,
    linear-gradient(120deg, color-mix(in srgb, var(--accent) 65%, transparent), color-mix(in srgb, var(--flash) 55%, transparent)) border-box;
  border: 1px solid transparent;
  box-shadow: var(--shadow-2);
  text-align: center; display: grid; justify-items: center; gap: 10px;
}
.cta-band::before {
  content: ""; position: absolute; inset: -40% auto auto 50%;
  transform: translateX(-50%);
  width: 560px; height: 320px;
  background: radial-gradient(circle, var(--accent-soft), transparent 65%);
  pointer-events: none;
}
.cta-band h2 { font-family: var(--font-display); font-size: clamp(1.7rem, 3.4vw, 2.5rem); margin: 0; letter-spacing: -.02em; }
.cta-band p { margin: 0; color: var(--muted); }
.cta-band .hero-cta { justify-content: center; margin-top: 8px; }

.home-section { margin-top: clamp(30px, 5vw, 56px); }
.home-section > h2 {
  font-family: var(--font-display);
  font-size: clamp(1.5rem, 2.6vw, 2.05rem);
  letter-spacing: -.015em; margin: 0 0 6px;
}
.home-section > .sub { color: var(--muted); margin: 0 0 18px; max-width: 62ch; }

.syl-grid { display: grid; grid-template-columns: minmax(0, 1fr); gap: 12px; }
.syl-card {
  position: relative; display: block;
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--r-l); padding: 18px 18px 16px;
  color: var(--text); text-decoration: none;
  box-shadow: var(--shadow-1);
  transition: transform var(--t-med) var(--ease), border-color var(--t-fast), box-shadow var(--t-med) var(--ease);
}
.syl-card:hover { text-decoration: none; transform: translateY(-2px); border-color: var(--line-strong); box-shadow: var(--shadow-2); }
.syl-card .kicker { display: flex; align-items: center; gap: 8px; margin-bottom: 8px; }
.syl-card .n {
  font-family: var(--font-mono); font-size: .72rem;
  background: var(--accent-soft); color: var(--accent);
  border: 1px solid color-mix(in srgb, var(--accent) 35%, transparent);
  padding: 2px 8px; border-radius: 99px;
}
.syl-card h3 { font-family: var(--font-display); font-size: 1.22rem; margin: 0 0 6px; letter-spacing: -.01em; }
.syl-card p { margin: 0; color: var(--muted); font-size: .93rem; line-height: 1.55; }
.syl-meta { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 12px; align-items: center; }
.chip {
  font-family: var(--font-mono); font-size: .7rem;
  color: var(--dim); background: var(--surface-2);
  border: 1px solid var(--line); border-radius: 99px;
  padding: 3px 9px;
}
.chip.good { color: var(--good); background: var(--good-soft); border-color: color-mix(in srgb, var(--good) 35%, transparent); }

/* ---------- lesson ---------- */
.lesson-head { margin: 8px 0 26px; max-width: 42em; }
.lesson-head .kicker { display: flex; align-items: center; gap: 10px; margin-bottom: 10px; }
.lesson-head h1 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 4.6vw, 3.1rem);
  line-height: 1.06; letter-spacing: -.02em; margin: 0 0 .35em;
}
.lesson-head .sub { color: var(--muted); font-size: clamp(1.05rem, 1.5vw, 1.2rem); line-height: 1.55; margin: 0; }
.lesson-head .meta { margin-top: 14px; display: flex; gap: 8px; flex-wrap: wrap; }

.prose { max-width: 42em; }
.prose p { margin: 0 0 1.15em; }
.prose p.lead { font-size: 1.12em; line-height: 1.65; color: var(--text); }
.prose h2 {
  font-family: var(--font-display);
  font-size: clamp(1.45rem, 2.4vw, 1.9rem);
  letter-spacing: -.015em; line-height: 1.2;
  margin: 2.2em 0 .7em;
}
.prose h3 {
  font-family: var(--font-display);
  font-size: clamp(1.16rem, 1.7vw, 1.35rem);
  margin: 1.9em 0 .55em; letter-spacing: -.01em;
}
.prose ul.prose-list { margin: 0 0 1.2em; padding-left: 0; list-style: none; display: grid; gap: 8px; }
.prose ul.prose-list li { position: relative; padding-left: 26px; }
.prose ul.prose-list li::before {
  content: ""; position: absolute; left: 4px; top: .62em;
  width: 8px; height: 8px; border-radius: 3px;
  background: var(--accent); opacity: .85;
}
.prose strong { font-weight: 650; }
.prose code, .mono {
  font-family: var(--font-mono); font-size: .85em;
  background: var(--surface-2); border: 1px solid var(--line);
  border-radius: 6px; padding: .1em .38em;
}

/* term chip — dotted chip + help cursor = “hover for definition” */
.term {
  font: inherit; font-weight: 600; color: var(--text);
  background: var(--accent-soft);
  border-bottom: 1.5px dotted var(--accent);
  padding: 1px 6px; border-radius: 6px;
  cursor: help;
  transition: background var(--t-fast), color var(--t-fast);
}
.term:hover, .term[aria-expanded="true"] {
  background: color-mix(in srgb, var(--accent) 24%, transparent);
  color: var(--accent);
}
.term-tip {
  position: absolute; z-index: 300;
  max-width: min(340px, calc(100vw - 24px));
  background: var(--surface-3); border: 1px solid var(--line-strong);
  border-radius: 12px; padding: 10px 14px;
  box-shadow: var(--shadow-2);
  opacity: 0; visibility: hidden;
  transition: opacity var(--t-fast);
  pointer-events: none;
}
.term-tip.show { opacity: 1; visibility: visible; }
.term-tip .tt-term {
  font-family: var(--font-mono); font-size: .68rem;
  letter-spacing: .1em; text-transform: uppercase; color: var(--accent);
  margin-bottom: 3px;
}
.term-tip .tt-def { font-size: .9rem; color: var(--text); line-height: 1.55; }
.term-tip .tt-def b { font-weight: 650; }

/* analogy + watch cards */
.card-note {
  border-radius: var(--r-l);
  padding: 16px 18px 15px;
  margin: 1.6em 0;
  border: 1px solid var(--line);
  box-shadow: var(--shadow-1);
}
.card-note .cn-title {
  display: flex; align-items: center; gap: 8px;
  font-family: var(--font-mono); font-size: .72rem;
  letter-spacing: .12em; text-transform: uppercase; margin-bottom: 8px;
}
.card-note p { margin: 0 0 .7em; font-size: .97rem; line-height: 1.62; }
.card-note p:last-child { margin-bottom: 0; }
.card-note.analogy { background: var(--accent-soft); }
.card-note.analogy .cn-title { color: var(--accent); }
.card-note.watch { background: var(--warn-soft); }
.card-note.watch .cn-title { color: var(--warn); }
.card-note.good { background: var(--good-soft); }
.card-note.good .cn-title { color: var(--good); }

/* operator notice */
.notice-card {
  display: grid; gap: 6px;
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--r-m);
  padding: 14px 16px; margin: 1.5em 0;
  box-shadow: var(--shadow-1);
}
.notice-card .nc-head { display: flex; gap: 10px; align-items: baseline; flex-wrap: wrap; }
.notice-card .nc-when { font-family: var(--font-mono); font-size: .72rem; color: var(--dim); }
.notice-card .nc-who { font-family: var(--font-mono); font-size: .72rem; color: var(--pro); text-transform: uppercase; letter-spacing: .1em; }
.notice-card .nc-text { font-family: var(--font-display); font-size: 1.05rem; line-height: 1.5; }

/* code fixture */
pre.fixture {
  font-family: var(--font-mono);
  font-size: .8rem; line-height: 1.7;
  background: var(--bg-soft); border: 1px solid var(--line);
  border-radius: var(--r-m); padding: 14px 16px;
  overflow-x: auto; margin: 1.5em 0;
  color: var(--muted);
}
pre.fixture b { color: var(--text); font-weight: 600; }
pre.fixture .hi { color: var(--accent); }

/* data table */
.table-wrap { overflow-x: auto; margin: 1.5em 0; border: 1px solid var(--line); border-radius: var(--r-m); background: var(--surface); }
table.data { border-collapse: collapse; width: 100%; font-size: .88rem; min-width: 480px; }
table.data th {
  text-align: left; font-family: var(--font-mono); font-weight: 500;
  font-size: .7rem; letter-spacing: .08em; text-transform: uppercase; color: var(--dim);
  padding: 10px 14px; border-bottom: 1px solid var(--line-strong);
}
table.data td { padding: 10px 14px; border-bottom: 1px solid var(--line); vertical-align: top; }
table.data tr:last-child td { border-bottom: 0; }
table.data td.num { font-family: var(--font-mono); white-space: nowrap; }
table.data .swatch { display: inline-block; width: 9px; height: 9px; border-radius: 3px; margin-right: 7px; }

/* pull quote */
.pull {
  font-family: var(--font-display);
  font-size: clamp(1.25rem, 2.2vw, 1.6rem);
  line-height: 1.4; letter-spacing: -.01em;
  margin: 2em 0; color: var(--text);
}
.pull .attr { display: block; margin-top: 10px; font-family: var(--font-mono); font-size: .72rem; letter-spacing: .1em; text-transform: uppercase; color: var(--dim); }

/* ---------- chart card ---------- */
.chart-card {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--r-l); padding: 16px 16px 12px;
  margin: 1.8em 0; box-shadow: var(--shadow-1);
  max-width: 46em;
}
.chart-head { display: flex; justify-content: space-between; align-items: baseline; gap: 12px; flex-wrap: wrap; }
.chart-title { font-family: var(--font-mono); font-size: .82rem; font-weight: 600; color: var(--text); }
.chart-tag { font-family: var(--font-mono); font-size: .68rem; color: var(--dim); }
.chart-official { font-size: .8rem; color: var(--dim); margin: 6px 0 0; line-height: 1.5; }
.chart-body { position: relative; margin-top: 10px; }
.chart-svg { width: 100%; height: auto; display: block; overflow: visible; }
.chart-legend { display: flex; gap: 16px; flex-wrap: wrap; margin-top: 8px; font-family: var(--font-mono); font-size: .7rem; color: var(--muted); }
.chart-legend .li { display: flex; align-items: center; gap: 6px; }
.chart-legend .sw { width: 14px; height: 3px; border-radius: 2px; }
.chart-story {
  margin-top: 10px; padding-top: 10px;
  border-top: 1px dashed var(--line-strong);
  font-size: .9rem; color: var(--muted); line-height: 1.6;
}
.chart-story b { color: var(--text); }
.chart-tip {
  position: absolute; pointer-events: none; z-index: 5;
  background: var(--surface-3); border: 1px solid var(--line-strong);
  border-radius: 10px; padding: 7px 10px;
  font-family: var(--font-mono); font-size: .7rem; line-height: 1.5;
  box-shadow: var(--shadow-2); white-space: nowrap;
  transform: translate(-50%, calc(-100% - 12px));
  opacity: 0; transition: opacity var(--t-fast);
}
.chart-tip.show { opacity: 1; }
.chart-tip .t-step { color: var(--dim); }
.chart-line { fill: none; stroke-width: 2.2; stroke-linecap: round; stroke-linejoin: round; }
.chart-area { opacity: .1; }
.chart-grid-l { stroke: var(--line); stroke-width: 1; }
.chart-axis-t { font-family: var(--font-mono); font-size: 10px; fill: var(--dim); }
.chart-hover-l { stroke: var(--line-strong); stroke-width: 1; stroke-dasharray: 3 3; }
.chart-restart-l { stroke: var(--bad); stroke-width: 1; stroke-dasharray: 2 4; opacity: .55; }
.chart-anno { font-family: var(--font-mono); font-size: 9.5px; fill: var(--bad); }

/* ---------- take-the-test CTA ---------- */
.test-cta {
  position: relative; overflow: hidden;
  margin: 44px 0 10px; padding: 26px 24px;
  border-radius: var(--r-xl);
  background:
    linear-gradient(var(--surface), var(--surface)) padding-box,
    linear-gradient(120deg, color-mix(in srgb, var(--accent) 65%, transparent), color-mix(in srgb, var(--flash) 55%, transparent)) border-box;
  border: 1px solid transparent;
  box-shadow: var(--shadow-2);
  display: grid; gap: 8px;
}
.test-cta::before {
  content: ""; position: absolute; inset: auto -20% -60% auto;
  width: 320px; height: 320px; border-radius: 50%;
  background: radial-gradient(circle, var(--accent-soft), transparent 65%);
  pointer-events: none;
}
.test-cta h2 { font-family: var(--font-display); font-size: clamp(1.45rem, 2.6vw, 1.9rem); margin: 4px 0 2px; letter-spacing: -.015em; }
.test-cta p { margin: 0; color: var(--muted); max-width: 52ch; }
.test-cta .cta-row { display: flex; flex-wrap: wrap; align-items: center; gap: 14px; margin-top: 14px; }
.test-cta .cta-note { font-family: var(--font-mono); font-size: .72rem; color: var(--dim); }

/* ---------- buttons ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  min-height: 46px; padding: 10px 22px;
  border-radius: 14px; font-weight: 620; font-size: .95rem;
  border: 1px solid transparent; text-decoration: none;
  transition: transform var(--t-fast) var(--ease), background var(--t-fast), border-color var(--t-fast), box-shadow var(--t-fast), opacity var(--t-fast);
}
.btn:hover { text-decoration: none; }
.btn:active { transform: scale(.975); }
.btn[disabled] { opacity: .45; pointer-events: none; }
.btn-primary { background: var(--accent); color: var(--accent-ink); box-shadow: var(--shadow-1); }
.btn-primary:hover { filter: brightness(1.06); }
.btn-ghost { background: var(--surface); border-color: var(--line-strong); color: var(--text); }
.btn-ghost:hover { border-color: var(--accent); }
.btn-block { width: 100%; }
.btn-lg { min-height: 52px; padding: 12px 28px; font-size: 1.02rem; }

/* ---------- lesson nav ---------- */
.lesson-nav { display: grid; grid-template-columns: 1fr; gap: 12px; margin: 34px 0 8px; }
.lesson-nav a {
  display: grid; gap: 2px;
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--r-l); padding: 14px 18px;
  color: var(--text); text-decoration: none;
  transition: border-color var(--t-fast), transform var(--t-med) var(--ease);
}
.lesson-nav a:hover { border-color: var(--accent); transform: translateY(-2px); text-decoration: none; }
.lesson-nav .dir { font-family: var(--font-mono); font-size: .68rem; letter-spacing: .12em; text-transform: uppercase; color: var(--dim); }
.lesson-nav .ttl { font-family: var(--font-display); font-size: 1.05rem; font-weight: 650; }
.lesson-nav .next { text-align: right; }

/* ---------- rail ---------- */
.rail-card {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--r-l); padding: 16px; margin-bottom: 14px;
  box-shadow: var(--shadow-1);
}
.rail-card h4 { margin: 0 0 10px; font-family: var(--font-mono); font-size: .7rem; letter-spacing: .12em; text-transform: uppercase; color: var(--dim); font-weight: 500; }
.toc { list-style: none; margin: 0; padding: 0; display: grid; gap: 2px; }
.toc a {
  display: block; padding: 6px 10px; border-radius: 8px;
  color: var(--muted); font-size: .86rem; text-decoration: none;
}
.toc a:hover { color: var(--text); background: var(--surface-2); text-decoration: none; }
.toc a.active { color: var(--accent); background: var(--accent-soft); }
.rail-fact { display: flex; justify-content: space-between; gap: 10px; padding: 6px 0; border-bottom: 1px dashed var(--line); font-size: .84rem; }
.rail-fact:last-child { border-bottom: 0; }
.rail-fact .k { color: var(--dim); }
.rail-fact .v { font-family: var(--font-mono); font-size: .8rem; text-align: right; }

/* ---------- quiz layer ---------- */
.quiz-layer { position: fixed; inset: 0; z-index: 999; display: grid; isolation: isolate; }
.quiz-backdrop {
  position: absolute; inset: 0;
  background: rgba(5, 7, 11, .62);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  animation: fade-in var(--t-med) var(--ease);
}
.quiz-dialog {
  position: relative;
  z-index: 1;
  background: var(--bg-elev);
  border: 1px solid var(--line-strong);
  display: flex; flex-direction: column;
  width: 100%; height: 100%;
  overflow: hidden;
  animation: sheet-up .3s var(--ease);
}
.quiz-head {
  display: flex; align-items: center; gap: 12px;
  padding: calc(env(safe-area-inset-top) + 14px) 16px 12px;
  border-bottom: 1px solid var(--line);
}
.quiz-head .qh-text { min-width: 0; flex: 1; }
.quiz-head .qh-lesson {
  font-family: var(--font-mono); font-size: .66rem; letter-spacing: .12em;
  text-transform: uppercase; color: var(--dim);
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.quiz-head .qh-title { font-family: var(--font-display); font-size: 1.12rem; font-weight: 700; letter-spacing: -.01em; }
.quiz-count { font-family: var(--font-mono); font-size: .8rem; color: var(--muted); white-space: nowrap; }
.quiz-count b { color: var(--accent); }
.quiz-progress { height: 3px; background: var(--surface-2); flex: none; }
.quiz-progress .fill { height: 100%; background: linear-gradient(90deg, var(--accent), var(--flash)); transition: width var(--t-med) var(--ease); }

.quiz-body {
  flex: 1; min-height: 0; overflow-y: auto;
  padding: 20px 16px 12px;
  display: flex; flex-direction: column;
}
.q-stage { position: relative; flex: none; width: 100%; max-width: 720px; margin: 0 auto; transition: height .24s var(--ease); }
.q-card { position: absolute; inset: 0 0 auto 0; opacity: 1; }
.q-card.static { position: static; }
.q-card.anim-out-left { animation: q-out-left .18s var(--ease) forwards; }
.q-card.anim-out-right { animation: q-out-right .18s var(--ease) forwards; }
.q-card.anim-in-left { animation: q-in-left .22s var(--ease); }
.q-card.anim-in-right { animation: q-in-right .22s var(--ease); }

.q-text {
  font-family: var(--font-display);
  font-size: clamp(1.25rem, 2.4vw, 1.55rem);
  line-height: 1.35; letter-spacing: -.012em;
  margin: 0 0 18px;
}
.q-options { display: grid; gap: 10px; margin: 0; padding: 0; border: 0; }
.option {
  display: grid; grid-template-columns: 34px 1fr; align-items: center; gap: 12px;
  min-height: 56px; padding: 12px 16px;
  background: var(--surface); border: 1.5px solid var(--line);
  border-radius: var(--r-m); cursor: pointer;
  transition: border-color var(--t-fast), background var(--t-fast), transform var(--t-fast) var(--ease);
}
.option:hover { border-color: var(--line-strong); }
.option:active { transform: scale(.99); }
.option input { position: absolute; opacity: 0; pointer-events: none; }
.option .key {
  width: 32px; height: 32px; border-radius: 9px;
  display: grid; place-items: center;
  font-family: var(--font-mono); font-size: .8rem;
  background: var(--surface-2); border: 1px solid var(--line-strong); color: var(--muted);
  transition: all var(--t-fast);
}
.option .txt { font-size: 1rem; line-height: 1.5; }
.option.selected { border-color: var(--accent); background: var(--accent-soft); }
.option.selected .key { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); font-weight: 700; }
.option input:focus-visible + .key { outline: 2px solid var(--accent); outline-offset: 2px; }
.option.correct { border-color: var(--good); background: var(--good-soft); }
.option.correct .key { background: var(--good); border-color: var(--good); color: var(--accent-ink); }
.option.wrong { border-color: var(--bad); background: var(--bad-soft); }
.option.wrong .key { background: var(--bad); border-color: var(--bad); color: var(--accent-ink); }

.quiz-dots { display: flex; gap: 5px; align-items: center; padding: 18px 2px 6px; flex: none; width: 100%; max-width: 720px; margin: 0 auto; }
.qdot {
  position: relative; flex: 1;
  height: 6px; border-radius: 3px;
  background: var(--surface-3); border: 0; padding: 0;
  transition: background var(--t-fast), box-shadow var(--t-fast), transform var(--t-fast) var(--ease);
}
.qdot::after { content: ""; position: absolute; inset: -12px 0; border-radius: 4px; }
.qdot.answered { background: var(--muted); }
.qdot.ok { background: var(--good); }
.qdot.no { background: var(--bad); }
.qdot.current { box-shadow: 0 0 0 2px var(--accent); }
.qdot:hover { transform: scaleY(1.6); }
.qdot.streak-dot::before {
  content: ""; position: absolute; top: -8px; left: 50%; transform: translateX(-50%);
  width: 4px; height: 4px; border-radius: 50%; background: var(--warn);
}

.quiz-foot {
  display: flex; align-items: center; gap: 10px;
  padding: 12px 16px calc(env(safe-area-inset-bottom) + 16px);
  border-top: 1px solid var(--line);
  background: var(--bg-elev);
}
.quiz-foot .spacer { flex: 1; }
.streak-pill {
  font-family: var(--font-mono); font-size: .72rem; color: var(--accent);
  background: var(--accent-soft); border: 1px solid color-mix(in srgb, var(--accent) 32%, transparent);
  border-radius: 99px; padding: 5px 12px;
  opacity: 0; transition: opacity var(--t-fast);
}
.streak-pill.show { opacity: 1; }
.quiz-warn {
  color: var(--warn); font-size: .85rem;
  display: flex; align-items: center; gap: 8px;
}

/* results */
.results { width: 100%; max-width: 720px; margin: 0 auto; }
.results-hero { display: grid; justify-items: center; text-align: center; padding: 8px 0 18px; }
.score-ring-wrap { position: relative; width: 168px; height: 168px; }
.score-ring-wrap svg { width: 100%; height: 100%; }
.score-ring-bg { stroke: var(--surface-2); }
.score-ring-fg { stroke: var(--accent); stroke-linecap: round; transition: stroke-dashoffset 1s var(--ease); }
.score-num {
  position: absolute; inset: 0; display: grid; place-items: center;
  font-family: var(--font-display); font-size: 2.5rem; font-weight: 700; letter-spacing: -.02em;
}
.score-num small { font-size: 1.1rem; color: var(--dim); font-weight: 500; }
.score-band {
  margin-top: 16px;
  font-family: var(--font-display); font-size: clamp(1.3rem, 2.4vw, 1.7rem);
  letter-spacing: -.015em;
}
.score-sub { color: var(--muted); margin-top: 6px; max-width: 46ch; }
.results-actions { display: flex; flex-wrap: wrap; gap: 10px; justify-content: center; margin: 18px 0 26px; }

/* inline answer feedback */
.q-feedback {
  margin-top: 16px;
  border: 1px solid var(--line-strong);
  border-radius: var(--r-m);
  padding: 13px 15px;
  font-size: .93rem; line-height: 1.6;
  animation: rise-in .3s var(--ease);
}
.q-feedback.ok { background: var(--good-soft); border-color: color-mix(in srgb, var(--good) 40%, transparent); }
.q-feedback.no { background: var(--bad-soft); border-color: color-mix(in srgb, var(--bad) 40%, transparent); }
.qf-title { font-weight: 650; margin-bottom: 4px; }
.q-feedback.ok .qf-title { color: var(--good); }
.q-feedback.no .qf-title { color: var(--bad); }
.q-feedback .qf-title b { color: var(--good); }
.qf-why { color: var(--muted); }
.qf-why::before {
  content: "why — ";
  font-family: var(--font-mono); font-size: .68rem;
  letter-spacing: .1em; text-transform: uppercase; color: var(--dim);
}

/* end-of-test summary */
.score-split { margin-top: 12px; font-family: var(--font-mono); font-size: .82rem; color: var(--muted); }
.score-split .ok { color: var(--good); }
.score-split .no { color: var(--bad); }
.results-dots { display: flex; gap: 6px; justify-content: center; margin-top: 12px; }
.results-dots .rd { width: 26px; height: 7px; border-radius: 4px; background: var(--surface-2); }
.results-dots .rd.ok { background: var(--good); }
.results-dots .rd.no { background: var(--bad); }

/* ---------- footer ---------- */
.foot { border-top: 1px solid var(--line); margin-top: 40px; padding: 28px 16px calc(env(safe-area-inset-bottom) + 34px); }
.foot-inner { max-width: 1560px; margin: 0 auto; color: var(--dim); font-size: .85rem; }
.foot-lede { margin: 0 0 8px; max-width: 68ch; }
.foot-lede b { color: var(--muted); }
.foot-links { margin: 0; }
.foot-made {
  margin: 12px 0 0;
  font-family: var(--font-mono);
  font-size: .74rem;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--dim);
}
.foot-made b { color: var(--accent); font-weight: 600; letter-spacing: .18em; }

/* ---------- animations ---------- */
@keyframes fade-in { from { opacity: 0; } to { opacity: 1; } }
@keyframes rise-in { from { opacity: 0; transform: translateY(14px); } to { opacity: 1; transform: none; } }

/* ---------- diagram animations ---------- */
@keyframes dg-draw { to { stroke-dashoffset: 0; } }
@keyframes dg-flow { to { stroke-dashoffset: -28; } }
@keyframes dg-pulse { 0%, 100% { opacity: .12; transform: scale(1); } 55% { opacity: .85; transform: scale(1.8); } }
@keyframes dg-fade { to { opacity: 1; } }
@keyframes dg-rise { to { transform: scaleY(1); } }
@keyframes dg-travel-x {
  0% { transform: translateX(0); opacity: 0; }
  8% { opacity: 1; }
  92% { opacity: 1; }
  100% { transform: translateX(560px); opacity: 0; }
}
@keyframes dg-run {
  0% { transform: translateX(0); opacity: 0; }
  12% { opacity: 1; }
  88% { opacity: 1; }
  100% { transform: translateX(315px); opacity: 0; }
}
@keyframes dg-drift {
  0%, 100% { transform: translate(0, 0); }
  50% { transform: translate(5px, -7px); }
}
@keyframes dg-grow-x { from { transform: scaleX(0); } to { transform: scaleX(1); } }
@keyframes dg-travel-y {
  0% { transform: translateY(0); opacity: 0; }
  10% { opacity: 1; }
  90% { opacity: 1; }
  100% { transform: translateY(-185px); opacity: 0; }
}
.dg-drift { transform-box: fill-box; animation: dg-drift 3.4s ease-in-out infinite; }
.dg-grow-x { transform-box: fill-box; transform-origin: left; animation: dg-grow-x 1.4s var(--ease) forwards; }
.dg-travel-y { animation: dg-travel-y 4.5s cubic-bezier(.35, 0, .65, 1) infinite; }
.dg-draw { stroke-dasharray: 1200; stroke-dashoffset: 1200; animation: dg-draw 1.8s var(--ease) forwards; }
.dg-flow { stroke-dasharray: 5 9; animation: dg-flow 1s linear infinite; }
.dg-pulse { transform-box: fill-box; transform-origin: center; animation: dg-pulse 2.6s var(--ease) infinite; }
.dg-fade { opacity: 0; animation: dg-fade .7s var(--ease) forwards; }
.dg-rise { transform-box: fill-box; transform-origin: bottom; transform: scaleY(0); animation: dg-rise .8s var(--ease) forwards; }
.dg-travel { animation: dg-travel-x 5.5s cubic-bezier(.35, 0, .65, 1) infinite; }
.dg-run { animation: dg-run 3s linear infinite; }
.dg-good { fill: var(--good); }
.dg-bad { fill: var(--bad); }
.dg-warn { fill: var(--warn); }
.dg-glow { filter: drop-shadow(0 0 6px var(--accent)); }
@keyframes sheet-up { from { opacity: 0; transform: translateY(26px) scale(.99); } to { opacity: 1; transform: none; } }
@keyframes q-out-left { to { opacity: 0; transform: translateX(-14px); } }
@keyframes q-out-right { to { opacity: 0; transform: translateX(14px); } }
@keyframes q-in-left { from { opacity: 0; transform: translateX(-14px); } }
@keyframes q-in-right { from { opacity: 0; transform: translateX(14px); } }
.anim-rise { animation: rise-in .5s var(--ease) backwards; }

/* ---------- responsive: tablet ---------- */
@media (min-width: 640px) {
  .main { padding: 30px 26px 72px; }
  .facts-strip { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .syl-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .stats-showcase { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .lesson-nav { grid-template-columns: 1fr 1fr; }
  .quiz-dialog {
    width: min(760px, calc(100vw - 48px));
    height: min(86dvh, 860px);
    margin: auto;
    border-radius: var(--r-xl);
    box-shadow: var(--shadow-3);
  }
  .quiz-layer { padding: 24px; }
  .quiz-head { padding: 16px 22px 12px; }
  .quiz-body { padding: 24px 22px 12px; }
  .quiz-foot { padding: 12px 22px 18px; }
}

/* ---------- responsive: desktop ---------- */
@media (min-width: 1024px) {
  .story-grid { grid-template-columns: 1.35fr 1fr; align-items: start; }
  .main { padding: 36px 44px 90px; }
  .syl-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .facts-strip { grid-template-columns: repeat(6, minmax(0, 1fr)); }
}

/* ---------- responsive: wide desktop ---------- */
@media (min-width: 1400px) {
  .layout { grid-template-columns: minmax(0, 1fr) 296px; }
  .rail { display: block; padding: 36px 20px 60px 0; }
  .rail-inner { position: sticky; top: calc(var(--topbar-h) + 28px); }
  .main { padding: 40px 56px 100px; }
}

/* ---------- responsive: 4K and ultrawide ---------- */
@media (min-width: 1920px) {
  .prose { max-width: 68ch; }
  .home-hero h1 { max-width: 15ch; }
  .chart-card { max-width: 50em; }
}
@media (min-width: 2560px) {
  .layout { max-width: 1720px; }
  .topbar-inner, .foot-inner { max-width: 1720px; }
  .syl-grid { grid-template-columns: repeat(4, minmax(0, 1fr)); }
}

/* ---------- reduced motion ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: .01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .01ms !important;
  }
}

/* ---------- print (bonus: readable handouts) ---------- */
@media print {
  .topbar, .sidebar, .rail, .quiz-layer, .test-cta, .lesson-nav { display: none !important; }
  body { background: #fff; color: #000; }
  .prose { max-width: none; }
}