:root {
  color-scheme: dark;
  --bg: #050505;
  --ink: #f3f6ea;
  --muted: #9aa394;
  --line: rgba(214, 255, 58, 0.16);
  --line-strong: rgba(214, 255, 58, 0.42);
  --surface: rgba(10, 10, 8, 0.78);
  --surface-strong: rgba(8, 8, 6, 0.9);
  --accent: #d6ff3a;
  --accent-dim: #9ec21f;
  --accent-soft: rgba(214, 255, 58, 0.1);
  --glow: 0 0 22px rgba(214, 255, 58, 0.28);
  --code-bg: #0b0d08;
  --code-chrome: #12150d;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }

html, body { min-height: 100%; }

body {
  margin: 0;
  background:
    radial-gradient(1200px 700px at 12% -10%, rgba(214, 255, 58, 0.06), transparent 55%),
    radial-gradient(900px 520px at 110% 8%, rgba(214, 255, 58, 0.04), transparent 50%),
    var(--bg);
  color: var(--ink);
}

.edge-physics-bg {
  position: fixed;
  inset: 0;
  z-index: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
}

.site-shell {
  position: relative;
  z-index: 1;
  width: min(100% - 2rem, 860px);
  margin: 0 auto;
  padding: 4.5rem 0 5rem;
}

.site-header { margin-bottom: 3rem; }

.eyebrow,
.lesson-number {
  color: var(--accent);
  font-size: .8rem;
  font-weight: 700;
  letter-spacing: .14em;
  margin: 0 0 1rem;
  text-transform: uppercase;
  text-shadow: 0 0 18px rgba(214, 255, 58, 0.45);
}

.lesson-number { margin-bottom: .9rem; }

h1, h2, h3 { line-height: 1.15; margin: 0; }
h1 { font-size: clamp(2.6rem, 7vw, 4.8rem); letter-spacing: -.05em; }
h2 { font-size: 1.25rem; }

.lede {
  color: var(--muted);
  font-size: 1.15rem;
  margin: 1rem 0 0;
}

.section-heading {
  align-items: baseline;
  display: flex;
  justify-content: space-between;
  margin-bottom: 1rem;
}

.course-count, time { color: var(--muted); font-size: .9rem; }

.course-list { display: grid; gap: .9rem; }

.course-card,
.empty-state,
.lesson-header,
.lesson-prose,
.course-home,
.note,
.flow,
.lesson-list a,
.agent-briefs {
  background: var(--surface);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--line);
}

.course-card {
  border-radius: 1rem;
  color: inherit;
  display: flex;
  gap: 1rem;
  justify-content: space-between;
  padding: 1.35rem 1.5rem;
  text-decoration: none;
  transition: border-color .16s ease, box-shadow .16s ease, transform .16s ease, background .16s ease;
}

.course-card:hover,
.course-card:focus-visible {
  border-color: var(--accent);
  background: rgba(16, 16, 10, 0.88);
  box-shadow: var(--glow);
  transform: translateY(-2px);
  animation: neon-flash .48s ease;
}

.course-card h3 { font-size: 1.1rem; }
.course-card p { color: var(--muted); margin: .5rem 0 0; }
.course-card time { flex: 0 0 auto; padding-top: .1rem; }

.empty-state {
  border-radius: 1rem;
  color: var(--muted);
  margin: 0;
  padding: 2rem;
  text-align: center;
}

.lesson { max-width: 760px; }

.lesson-header {
  border-radius: 1.1rem;
  margin-bottom: 1.25rem;
  padding: 1.7rem 1.5rem 1.6rem;
}

.lesson-header h1 { font-size: clamp(2.3rem, 6vw, 4rem); }

.lesson-lede {
  color: var(--muted);
  font-size: 1.2rem;
  line-height: 1.55;
  margin: 1rem 0 0;
}

.lesson-prose {
  border-radius: 1.1rem;
  font-size: 1.05rem;
  line-height: 1.7;
  padding: 1.5rem 1.5rem 1.7rem;
}

.lesson-prose h2 { font-size: 1.55rem; margin: 2.8rem 0 .85rem; }
.lesson-prose h3 { font-size: 1.15rem; margin: 2rem 0 .65rem; }
.lesson-prose p { margin: 0 0 1rem; }
.lesson-prose ul, .lesson-prose ol { margin: .6rem 0 1.3rem; padding-left: 1.35rem; }
.lesson-prose li { margin: .45rem 0; }
.lesson-prose a, .course-home a, .agent-brief a, .agent-briefs a { color: var(--accent); }
.lesson-prose a:hover, .course-home a:hover, .agent-brief a:hover, .agent-briefs a:hover { text-shadow: 0 0 12px rgba(214, 255, 58, 0.45); }

.lesson-prose code:not(pre code) {
  background: rgba(214, 255, 58, 0.1);
  border: 1px solid rgba(214, 255, 58, 0.14);
  border-radius: .3rem;
  color: #eef8b8;
  font-size: .92em;
  padding: .12em .3em;
}

.lesson-prose pre {
  background: var(--code-bg);
  border: 1px solid rgba(214, 255, 58, 0.12);
  border-radius: .7rem;
  color: #f3f6ea;
  font-size: .88rem;
  line-height: 1.55;
  margin: 1.2rem 0 1.5rem;
  overflow-x: auto;
  padding: 1.15rem 1.25rem;
}

.lesson-prose pre code {
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
}

.note {
  border-left: 4px solid var(--accent);
  border-radius: 0 .7rem .7rem 0;
  box-shadow: inset 0 0 0 1px rgba(214, 255, 58, 0.04);
  margin: 1.4rem 0;
  padding: 1rem 1.1rem;
}

.flow {
  align-items: stretch;
  border-radius: .8rem;
  display: flex;
  flex-wrap: wrap;
  gap: .65rem;
  margin: 1rem 0;
  padding: 1rem;
}

.flow-step {
  background: rgba(6, 6, 5, 0.72);
  border: 1px solid var(--line);
  border-radius: .65rem;
  display: flex;
  flex: 1 1 9rem;
  flex-direction: column;
  gap: .25rem;
  justify-content: center;
  min-width: 9rem;
  padding: .8rem .9rem;
}

.flow-label {
  color: var(--accent);
  font-size: .75rem;
  font-weight: 700;
  letter-spacing: .06em;
  text-transform: uppercase;
}

.flow-step strong { line-height: 1.3; }

.flow-arrow {
  align-items: center;
  color: var(--accent-dim);
  display: flex;
  font-size: 1.35rem;
  font-weight: 600;
  justify-content: center;
  padding: 0 .1rem;
}

.course-home {
  border-radius: 1.1rem;
  margin-bottom: 2.5rem;
  padding: 1.7rem 1.5rem 1.6rem;
}

.course-home h1 { font-size: clamp(2.4rem, 6vw, 4.2rem); }
.course-home .outcome { font-size: 1.2rem; line-height: 1.55; margin: 1rem 0 .6rem; }
.course-home .audience { color: var(--muted); margin: 0; }

.lesson-list {
  counter-reset: lessons;
  display: grid;
  gap: .7rem;
  list-style: none;
  margin: 1rem 0 0;
  padding: 0;
}

.lesson-list li { counter-increment: lessons; background: none; border: 0; }

.lesson-list a {
  align-items: center;
  border-radius: .7rem;
  color: inherit;
  display: flex;
  gap: .8rem;
  padding: .95rem 1rem;
  text-decoration: none;
  transition: border-color .16s ease, box-shadow .16s ease, transform .16s ease;
}

.lesson-list a::before {
  color: var(--accent);
  content: counter(lessons, decimal-leading-zero);
  font-weight: 700;
  text-shadow: 0 0 12px rgba(214, 255, 58, 0.35);
}

.lesson-list a:hover,
.lesson-list a:focus-visible {
  border-color: var(--accent);
  box-shadow: var(--glow);
  transform: translateX(2px);
}

.lesson-nav {
  border-top: 1px solid var(--line-strong);
  display: flex;
  gap: 1rem;
  justify-content: space-between;
  margin-top: 3rem;
  padding-top: 1.2rem;
}

.lesson-nav a {
  color: var(--accent);
  font-weight: 600;
  text-decoration: none;
}

.lesson-nav a:hover { text-shadow: 0 0 12px rgba(214, 255, 58, 0.45); }
.lesson-nav a:last-child { text-align: right; }

.back-link {
  color: var(--muted);
  display: inline-block;
  font-size: .92rem;
  margin-bottom: 1.5rem;
  text-decoration: none;
}

.back-link:hover { color: var(--accent); }

.site-footer {
  border-top: 1px solid var(--line-strong);
  color: var(--muted);
  font-size: .88rem;
  line-height: 1.5;
  margin-top: 3.5rem;
  padding-top: 1.25rem;
}

.site-footer p { margin: 0 0 .35rem; }
.site-footer p:last-child { margin-bottom: 0; }

.agent-brief { color: var(--muted); font-size: .9rem; margin: -.75rem 0 1.5rem; }
.agent-briefs { border-radius: 1rem; margin-top: 2.5rem; padding: 1.2rem 1.35rem 1.35rem; }
.agent-briefs ul { margin: 1rem 0 0; padding-left: 1.25rem; }
.agent-briefs li { margin: .45rem 0; }

.code-block {
  background: var(--code-bg);
  border: 1px solid rgba(214, 255, 58, 0.14);
  border-radius: .7rem;
  box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.4);
  margin: 1.2rem 0 1.5rem;
  overflow: hidden;
  position: relative;
}

.code-block__header {
  align-items: center;
  background: var(--code-chrome);
  border-bottom: 1px solid rgba(214, 255, 58, 0.1);
  color: #c6d38a;
  display: flex;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: .72rem;
  justify-content: space-between;
  letter-spacing: .04em;
  min-height: 2.35rem;
  padding: .45rem .65rem .45rem 1.25rem;
  text-transform: uppercase;
}

.code-block__label { opacity: .85; }

.copy-btn {
  background: transparent;
  border: 1px solid rgba(214, 255, 58, 0.35);
  border-radius: .35rem;
  color: var(--ink);
  cursor: pointer;
  font: inherit;
  letter-spacing: 0;
  padding: .3rem .6rem;
  text-transform: none;
}

.copy-btn:hover,
.copy-btn:focus-visible {
  background: rgba(214, 255, 58, 0.12);
  border-color: var(--accent);
  box-shadow: var(--glow);
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.lesson-prose .code-block pre {
  background: transparent;
  border: 0;
  border-radius: 0;
  margin: 0;
  overflow-x: auto;
  padding: 1rem 1.25rem 1.15rem;
}

.lesson-prose .code-block pre code.hljs { background: transparent; padding: 0; }
.lesson-prose .code-block pre code { display: block; min-width: max-content; }

@keyframes neon-flash {
  0%, 100% { box-shadow: var(--glow); }
  35% { box-shadow: 0 0 0 1px var(--accent), 0 0 28px rgba(214, 255, 58, 0.55); }
}

@media (max-width: 600px) {
  .site-shell { padding-top: 3rem; }
  .course-card { display: block; }
  .course-card time { display: block; margin-top: 1rem; }
  .lesson-header, .lesson-prose, .course-home { padding-left: 1.15rem; padding-right: 1.15rem; }
  .lesson-nav { align-items: flex-start; flex-direction: column; }
  .lesson-nav a:last-child { text-align: left; }
  .code-block__header { padding-left: .85rem; }
  .lesson-prose .code-block pre { padding-left: .85rem; padding-right: .85rem; }
}

@media (prefers-reduced-motion: reduce) {
  .course-card,
  .lesson-list a,
  .copy-btn {
    transition: none;
  }

  .course-card:hover,
  .course-card:focus-visible,
  .lesson-list a:hover,
  .lesson-list a:focus-visible {
    animation: none;
    transform: none;
  }
}