:root {
  --bg: #0b0d10;
  --surface: #14171c;
  --border: #1f2937;
  --code-bg: #0a0c0f;
  --fg: #e4e6eb;
  --muted: #9ca3af;
  --accent: #4ade80;
  --link: #60a5fa;
  --warn: #f59e0b;
  --danger: #ef4444;
  --display: 'Inter', system-ui, -apple-system, sans-serif;
  --mono: 'JetBrains Mono', ui-monospace, 'SF Mono', monospace;

  --container: min(70rem, 92vw);
  --content: min(70ch, 92vw);
  --radius: 6px;
  --radius-lg: 12px;
  --gap: 1rem;
  --space: 2rem;
}

* { box-sizing: border-box; }

html {
  background: var(--bg);
  color: var(--fg);
  font-family: var(--display);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

a { color: var(--link); text-decoration: none; }
a:hover, a:focus-visible { text-decoration: underline; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

h1, h2, h3, h4 { font-family: var(--display); line-height: 1.25; margin: 0 0 0.6em; letter-spacing: -0.01em; }
h1 { font-size: clamp(1.8rem, 4vw, 2.6rem); font-weight: 700; }
h2 { font-size: clamp(1.4rem, 3vw, 1.9rem); font-weight: 700; margin-top: 2em; }
h3 { font-size: 1.2rem; font-weight: 600; margin-top: 1.5em; }
h4 { font-size: 1rem; font-weight: 600; }

p { margin: 0 0 1em; }
ul, ol { padding-left: 1.4em; }
li { margin-bottom: 0.4em; }
code { font-family: var(--mono); font-size: 0.92em; }
:not(pre) > code { background: var(--code-bg); padding: 0.1em 0.4em; border-radius: 3px; border: 1px solid var(--border); }

table { border-collapse: collapse; width: 100%; margin: 1em 0; }
th, td { text-align: left; padding: 0.6em 0.8em; border-bottom: 1px solid var(--border); }
th { color: var(--muted); font-weight: 600; }

/* ============== nav ============== */
.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  gap: 0.4rem 1rem;
  flex-wrap: wrap;
  padding: 0.7rem 1.2rem;
  background: color-mix(in srgb, var(--bg) 80%, transparent);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.nav-brand {
  font-family: var(--mono);
  font-weight: 500;
  color: var(--fg);
  font-size: 1rem;
  margin-right: auto;
  display: flex;
  align-items: baseline;
  gap: 0.5em;
}
.nav-brand-sub { color: var(--muted); font-size: 0.85em; }
.nav-link {
  color: var(--muted);
  font-size: 0.92rem;
  padding: 0.35rem 0.7rem;
  border-radius: var(--radius);
}
.nav-link:hover, .nav-link:focus-visible { color: var(--fg); background: var(--surface); text-decoration: none; }
.nav-link.is-complete::after { content: " ●"; color: var(--accent); }
.nav-cta {
  background: var(--accent);
  color: var(--bg);
  font-weight: 600;
  padding: 0.45rem 0.9rem;
  border-radius: var(--radius);
  font-size: 0.92rem;
}
.nav-cta:hover, .nav-cta:focus-visible { background: color-mix(in srgb, var(--accent) 85%, white); text-decoration: none; }
.nav-progress {
  width: 80px;
  height: 6px;
  appearance: none;
  border: 1px solid var(--border);
  border-radius: 3px;
  background: var(--surface);
  overflow: hidden;
}
.nav-progress::-webkit-progress-bar { background: var(--surface); }
.nav-progress::-webkit-progress-value { background: var(--accent); }
.nav-progress::-moz-progress-bar { background: var(--accent); }

.nav-sections { position: relative; }
.nav-sections summary { list-style: none; cursor: pointer; }
.nav-sections summary::-webkit-details-marker { display: none; }
.nav-sections-menu {
  position: absolute;
  top: 110%;
  left: 0;
  min-width: 22rem;
  max-width: 90vw;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.4rem;
  display: flex;
  flex-direction: column;
  gap: 0.1rem;
  box-shadow: 0 12px 30px rgba(0,0,0,0.4);
}
.nav-sections-menu .nav-link { padding: 0.5rem 0.75rem; font-size: 0.88rem; }

/* ============== container ============== */
.container, main {
  width: var(--container);
  margin: 0 auto;
  padding: 2rem 0 4rem;
  flex-grow: 1;
}
main > * { max-width: var(--content); }
main > .section-meta, main > h1, main > .section-body, main > .quiz, main > .checklist, main > .complete-toggle, main > .section-nav { width: 100%; }

/* ============== hero ============== */
.hero { padding: 3rem 0 2rem; border-bottom: 1px solid var(--border); }
.hero-inner { width: var(--container); margin: 0 auto; padding: 0 0 1rem; }
.hero-ascii {
  font-family: var(--mono);
  color: var(--muted);
  font-size: clamp(0.55rem, 1.1vw, 0.85rem);
  line-height: 1.3;
  margin: 0 0 2rem;
  padding: 1rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow-x: auto;
  white-space: pre;
}
.hero h1 { font-size: clamp(2rem, 5vw, 3.4rem); margin-bottom: 0.5em; }
.hero-subhead { color: var(--muted); font-size: clamp(1rem, 1.5vw, 1.2rem); max-width: 60ch; }
.hero-ctas { display: flex; gap: 0.8rem; margin-top: 1.5rem; flex-wrap: wrap; }
.hero-cta-primary {
  background: var(--accent);
  color: var(--bg);
  font-weight: 600;
  padding: 0.8rem 1.4rem;
  border-radius: var(--radius);
  font-size: 1rem;
}
.hero-cta-primary:hover, .hero-cta-primary:focus-visible { background: color-mix(in srgb, var(--accent) 85%, white); text-decoration: none; }
.hero-cta-secondary {
  border: 1px solid var(--border);
  color: var(--fg);
  padding: 0.8rem 1.4rem;
  border-radius: var(--radius);
  font-size: 1rem;
}
.hero-cta-secondary:hover, .hero-cta-secondary:focus-visible { border-color: var(--fg); text-decoration: none; }

/* ============== section meta ============== */
.section-meta {
  display: flex;
  gap: 0.8rem;
  font-family: var(--mono);
  font-size: 0.85rem;
  color: var(--muted);
  margin-bottom: 1rem;
  flex-wrap: wrap;
}
.section-meta-num, .section-meta-time, .section-meta-layer {
  padding: 0.2rem 0.6rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
}
.section-meta-layer { color: var(--accent); border-color: color-mix(in srgb, var(--accent) 40%, var(--border)); }

/* ============== section body ============== */
.section-body { font-size: 1.02rem; }
.section-body p, .section-body ul, .section-body ol { max-width: 70ch; }
.section-body section + section { margin-top: 2.5rem; }
.section-body blockquote {
  border-left: 3px solid var(--accent);
  margin: 1.5em 0;
  padding: 0.2em 0 0.2em 1em;
  color: var(--muted);
}
.section-body strong { color: var(--fg); }

/* ============== code ============== */
.code-block {
  position: relative;
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem 1rem 1rem;
  margin: 1.2rem 0;
  overflow-x: auto;
  font-family: var(--mono);
  font-size: 0.9rem;
  line-height: 1.55;
}
.code-block code { background: transparent; border: 0; padding: 0; }
.code-copy-btn {
  position: absolute;
  top: 0.5rem;
  right: 0.5rem;
  background: var(--surface);
  color: var(--muted);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 0.3rem 0.6rem;
  font-family: var(--mono);
  font-size: 0.75rem;
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.12s ease;
}
.code-block:hover .code-copy-btn,
.code-block:focus-within .code-copy-btn { opacity: 1; }
.code-copy-btn:hover { color: var(--fg); border-color: var(--fg); }
.code-copy-btn[data-state="copied"] { color: var(--accent); border-color: var(--accent); }

/* ============== quiz ============== */
.quiz, .checklist {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.4rem;
  margin: 2.2rem 0 1rem;
}
.quiz h2, .checklist h2 { margin-top: 0; font-size: 1.1rem; color: var(--muted); text-transform: uppercase; letter-spacing: 0.06em; }
.quiz-question { margin: 0 0 1.5rem; padding-bottom: 1.2rem; border-bottom: 1px dashed var(--border); }
.quiz-question:last-child { border-bottom: 0; padding-bottom: 0; margin-bottom: 0; }
.quiz-question > p { font-weight: 600; }
.quiz-options { display: flex; flex-direction: column; gap: 0.5rem; margin: 0.7rem 0; }
.quiz-option {
  text-align: left;
  background: var(--bg);
  color: var(--fg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.7rem 0.9rem;
  font: inherit;
  cursor: pointer;
  transition: border-color 0.12s ease, background 0.12s ease;
}
.quiz-option:hover:not(:disabled) { border-color: var(--fg); }
.quiz-option:disabled { cursor: default; opacity: 0.85; }
.quiz-option.quiz-correct {
  border-color: var(--accent);
  background: color-mix(in srgb, var(--accent) 12%, var(--bg));
}
.quiz-option.quiz-incorrect {
  border-color: var(--danger);
  background: color-mix(in srgb, var(--danger) 12%, var(--bg));
}
.quiz-explanation {
  margin-top: 0.7rem;
  padding: 0.7rem 0.9rem;
  border-radius: var(--radius);
  background: var(--bg);
  color: var(--muted);
  border-left: 3px solid var(--accent);
  font-size: 0.95rem;
}
.quiz-explanation[hidden] { display: none; }

/* ============== checklist ============== */
.checklist-item {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0.6rem 0.8rem;
  padding: 0.6rem 0.4rem;
  border-bottom: 1px dashed var(--border);
  cursor: pointer;
}
.checklist-item:last-child { border-bottom: 0; }
.checklist-item input[type="checkbox"] {
  margin-top: 0.25em;
  width: 1.05em;
  height: 1.05em;
  accent-color: var(--accent);
}
.checklist-item small {
  color: var(--muted);
  display: block;
  margin-top: 0.2em;
  font-size: 0.85rem;
  grid-column: 2;
}
.checklist-item input:checked + span { color: var(--muted); text-decoration: line-through; }

/* ============== complete toggle ============== */
.complete-toggle {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--accent);
  color: var(--bg);
  border: 1px solid var(--accent);
  border-radius: var(--radius);
  padding: 0.7rem 1.2rem;
  font: inherit;
  font-weight: 600;
  cursor: pointer;
  margin: 1.5rem 0;
}
.complete-toggle:hover, .complete-toggle:focus-visible {
  background: color-mix(in srgb, var(--accent) 85%, white);
}
.complete-toggle[aria-pressed="true"] {
  background: transparent;
  color: var(--accent);
}
.complete-toggle[aria-pressed="true"] .complete-toggle-label::before {
  content: "✓ ";
}

/* ============== section nav ============== */
.section-nav {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin: 3rem 0 1rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border);
}
.section-nav-prev, .section-nav-next {
  padding: 0.8rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--fg);
  font-size: 0.95rem;
}
.section-nav-prev:hover, .section-nav-next:hover { border-color: var(--fg); text-decoration: none; }

/* ============== value prop ============== */
.value-prop {
  width: var(--container);
  margin: 3rem auto;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(18rem, 1fr));
  gap: 1.2rem;
}
.value-prop-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.6rem;
}
.value-prop-card h3 { margin-top: 0; color: var(--accent); font-family: var(--mono); font-size: 1.05rem; }
.value-prop-card p { margin-bottom: 0; color: var(--muted); }

/* ============== course outline ============== */
.course-outline { width: var(--container); margin: 4rem auto; }
.course-outline > h2 { margin-bottom: 1.5rem; }
.course-outline-item {
  display: grid;
  grid-template-columns: auto 1fr;
  grid-template-rows: auto auto;
  grid-template-areas: "num title" "num oneliner";
  gap: 0.2rem 1rem;
  padding: 1rem 1.2rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--fg);
  margin-bottom: 0.5rem;
  text-decoration: none;
}
.course-outline-item:hover, .course-outline-item:focus-visible {
  border-color: var(--accent);
  text-decoration: none;
}
.course-outline-num {
  grid-area: num;
  align-self: center;
  font-family: var(--mono);
  color: var(--accent);
  font-size: 1.4rem;
  font-weight: 600;
  min-width: 2.5em;
}
.course-outline-title { grid-area: title; font-weight: 600; }
.course-outline-oneliner { grid-area: oneliner; color: var(--muted); font-size: 0.92rem; }

/* ============== services ============== */
.services { width: var(--container); margin: 4rem auto; }
.services > h2 { margin-bottom: 0.5rem; }
.services-subhead {
  color: var(--muted);
  margin: 0 0 2rem;
  max-width: 70ch;
}
.services-subhead a { color: var(--link); }
.services-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(20rem, 1fr));
  gap: 1.2rem;
}
.services-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.6rem;
  display: flex;
  flex-direction: column;
}
.services-card h3 {
  margin: 0 0 0.3em;
  color: var(--accent);
  font-family: var(--mono);
  font-size: 1.1rem;
}
.services-card-tagline {
  margin: 0 0 0.8em;
  color: var(--fg);
  font-weight: 600;
  font-size: 0.95rem;
}
.services-card p:not(.services-card-tagline) {
  color: var(--muted);
  flex-grow: 1;
  margin-bottom: 1rem;
}
.services-cta {
  display: inline-flex;
  align-items: center;
  align-self: flex-start;
  margin-top: auto;
  font-family: var(--mono);
  color: var(--link);
  font-size: 0.9rem;
  border-bottom: 1px solid transparent;
}
.services-cta::after { content: " →"; padding-left: 0.3em; }
.services-cta:hover { border-bottom-color: var(--link); text-decoration: none; }

/* nav-vea — vExpertAI external link in nav */
.nav-vea { color: var(--accent); font-family: var(--mono); font-size: 0.88rem; }

/* ============== faq ============== */
.faq { width: var(--container); margin: 4rem auto; }
.faq > h2 { margin-bottom: 1.5rem; }
.faq-item {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-bottom: 0.6rem;
  overflow: hidden;
}
.faq-question {
  padding: 1rem 1.2rem;
  cursor: pointer;
  font-weight: 600;
  list-style: none;
}
.faq-question::-webkit-details-marker { display: none; }
.faq-question::before { content: "▸ "; color: var(--accent); display: inline-block; transition: transform 0.12s ease; }
.faq-item[open] .faq-question::before { transform: rotate(90deg); }
.faq-answer { padding: 0 1.2rem 1.2rem; color: var(--muted); }

/* ============== booking ============== */
.booking-embed {
  width: var(--container);
  margin: 4rem auto;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 2rem;
}
.booking-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr));
  gap: 1.2rem;
  margin: 1.5rem 0;
}
.booking-grid h4 { margin: 0 0 0.6em; color: var(--accent); font-family: var(--mono); font-size: 0.92rem; text-transform: uppercase; letter-spacing: 0.04em; }
.booking-grid ul { padding-left: 1.2em; }
.booking-grid li { color: var(--muted); margin-bottom: 0.3em; }
#cal-embed, .cal-embed {
  margin-top: 1.5rem;
  min-height: 600px;
  background: var(--bg);
  border-radius: var(--radius);
  border: 1px solid var(--border);
  overflow: hidden;
}

/* ============== footer ============== */
.footer {
  border-top: 1px solid var(--border);
  margin-top: auto;
  padding: 2rem;
  text-align: center;
  color: var(--muted);
  font-size: 0.92rem;
}
.footer-tagline { margin: 0 0 1rem; }
.footer nav { display: flex; justify-content: center; gap: 1rem; flex-wrap: wrap; }
.footer-link { color: var(--muted); padding: 0.3rem 0.6rem; border-radius: var(--radius); }
.footer-link:hover, .footer-link:focus-visible { color: var(--fg); background: var(--surface); text-decoration: none; }

/* ============== glossary ============== */
.glossary-list { display: grid; gap: 1.2rem; }
.glossary-list dt { font-family: var(--mono); color: var(--accent); font-weight: 600; margin-top: 0.5em; }
.glossary-list dd { margin: 0.3em 0 0; color: var(--fg); padding-left: 1em; border-left: 2px solid var(--border); }

/* ============== cheat sheet ============== */
.cheatsheet-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(20rem, 1fr));
  gap: 1.2rem;
}
.cheatsheet-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.2rem;
}
.cheatsheet-card h3 { margin-top: 0; color: var(--accent); font-family: var(--mono); font-size: 1rem; }
.cheatsheet-card pre { margin: 0.5rem 0; }

/* ============== mobile ============== */
@media (max-width: 720px) {
  .nav { padding: 0.6rem 0.8rem; gap: 0.3rem; }
  .nav-brand-sub { display: none; }
  .nav-link { padding: 0.3rem 0.5rem; font-size: 0.88rem; }
  .nav-progress { display: none; }
  .nav-sections-menu { left: -1rem; min-width: 18rem; }
  .container, main, .value-prop, .course-outline, .faq, .booking-embed { width: 92vw; }
  .hero { padding: 2rem 0 1.5rem; }
  .hero h1 { font-size: 2rem; }
  .booking-embed { padding: 1.2rem; }
}

/* ============== print (cheat sheet) ============== */
@media print {
  .nav, .footer, .complete-toggle, .quiz, .checklist, .section-nav, .nav-cta, .nav-progress { display: none !important; }
  body, html { background: white; color: black; }
  a { color: black; text-decoration: underline; }
  .code-block { background: #f5f5f5; color: black; border: 1px solid #ccc; page-break-inside: avoid; }
  .cheatsheet-card { border: 1px solid #ccc; background: white; page-break-inside: avoid; }
  h1, h2, h3 { color: black; }
  .container, main { padding-top: 0; }
}