/* =========================================================================
   Obsidian Lab — liquid glass on deep black
   Real-Time Operating Systems / Synchronization Tools
   ========================================================================= */

@import url('https://fonts.googleapis.com/css2?family=Geist:wght@300;400;500;600;700&family=JetBrains+Mono:wght@400;500;700&display=swap');

:root {
  /* Surface colors */
  --bg-0: #05060A;
  --bg-1: #0A0C13;
  --glass-bg: rgba(255, 255, 255, 0.045);
  --glass-bg-hover: rgba(255, 255, 255, 0.07);
  --glass-border: rgba(255, 255, 255, 0.085);
  --glass-border-strong: rgba(255, 255, 255, 0.18);
  --glass-shine: rgba(255, 255, 255, 0.14);

  /* Text */
  --text-1: rgba(255, 255, 255, 0.96);
  --text-2: rgba(255, 255, 255, 0.66);
  --text-3: rgba(255, 255, 255, 0.42);

  /* Accents */
  --mint: #39FFB0;
  --mint-soft: rgba(57, 255, 176, 0.16);
  --amber: #FFB547;
  --amber-soft: rgba(255, 181, 71, 0.16);
  --coral: #FF5C7A;
  --coral-soft: rgba(255, 92, 122, 0.16);
  --violet: #8B7CFF;
  --violet-soft: rgba(139, 124, 255, 0.16);
  --cyan: #5BE0FF;

  /* Motion */
  --ease-out: cubic-bezier(0.22, 0.61, 0.36, 1);
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);

  /* Layout */
  --radius-lg: 22px;
  --radius-md: 14px;
  --radius-sm: 8px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg-0);
  color: var(--text-1);
  font-family: 'Geist', -apple-system, BlinkMacSystemFont, sans-serif;
  font-feature-settings: 'ss01', 'ss02';
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  min-height: 100dvh;
  overflow-x: hidden;
}

/* ---------- Background scenery ---------- */

body::before {
  /* Slow-moving radial cyan glow. */
  content: '';
  position: fixed;
  inset: -20% -20% -20% -20%;
  background:
    radial-gradient(60% 40% at 20% 15%,  rgba(91, 224, 255, 0.16) 0%, transparent 60%),
    radial-gradient(50% 50% at 85% 80%,  rgba(139, 124, 255, 0.10) 0%, transparent 60%),
    radial-gradient(40% 30% at 60% 50%,  rgba(57, 255, 176, 0.06) 0%, transparent 70%);
  filter: blur(40px);
  z-index: 0;
  animation: drift 26s ease-in-out infinite alternate;
  pointer-events: none;
}

body::after {
  /* Faint schematic grid + film grain. */
  content: '';
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(rgba(255,255,255,0.025) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,0.025) 1px, transparent 1px);
  background-size: 56px 56px, 56px 56px;
  mask-image: radial-gradient(ellipse at center, black 30%, transparent 80%);
  z-index: 0;
  pointer-events: none;
}

@keyframes drift {
  from { transform: translate3d(0, 0, 0) scale(1); }
  to   { transform: translate3d(2%, -3%, 0) scale(1.06); }
}

@media (prefers-reduced-motion: reduce) {
  body::before { animation: none; }
}

/* ---------- Shell ---------- */

.shell {
  position: relative;
  z-index: 1;
  max-width: 1240px;
  margin: 0 auto;
  padding: 28px 24px 80px;
}

@media (max-width: 640px) {
  .shell { padding: 16px 14px 64px; }
}

/* ---------- Top bar ---------- */

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 18px;
  border-radius: var(--radius-md);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  backdrop-filter: blur(18px) saturate(140%);
  -webkit-backdrop-filter: blur(18px) saturate(140%);
  position: sticky;
  top: 12px;
  z-index: 50;
  box-shadow: 0 14px 40px rgba(0,0,0,0.4);
}

.topbar-brand {
  display: flex;
  align-items: center;
  gap: 12px;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.topbar-brand .dot {
  width: 8px; height: 8px; border-radius: 50%;
  background: var(--mint);
  box-shadow: 0 0 12px var(--mint), 0 0 24px var(--mint);
  animation: pulse 1.8s ease-in-out infinite;
}

.topbar-brand .name {
  background: linear-gradient(135deg, #fff 0%, #b8c4d8 100%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.topbar-brand .sub {
  display: block;
  font-size: 11px;
  color: var(--text-3);
  font-weight: 400;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-top: 1px;
}

.topbar-status {
  display: flex; align-items: center; gap: 12px;
  font-size: 12px; color: var(--text-2);
  font-family: 'JetBrains Mono', monospace;
}

.topbar-status .ping {
  display: inline-block;
  width: 6px; height: 6px; border-radius: 50%;
  background: var(--mint);
  box-shadow: 0 0 8px var(--mint);
}

@keyframes pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50%      { opacity: 0.7; transform: scale(0.9); }
}

/* ---------- Hero ---------- */

.hero {
  margin: 36px 0 24px;
  padding: 38px 32px;
  border-radius: var(--radius-lg);
  background:
    linear-gradient(180deg, rgba(255,255,255,0.06) 0%, rgba(255,255,255,0.02) 100%),
    var(--glass-bg);
  border: 1px solid var(--glass-border);
  backdrop-filter: blur(28px) saturate(140%);
  -webkit-backdrop-filter: blur(28px) saturate(140%);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background: radial-gradient(800px 200px at 20% 0%, rgba(91, 224, 255, 0.12), transparent 60%);
  pointer-events: none;
}

.hero h1 {
  margin: 0;
  font-size: clamp(28px, 4.6vw, 48px);
  line-height: 1.05;
  letter-spacing: -0.025em;
  font-weight: 600;
  background: linear-gradient(180deg, #fff 0%, #aab4c8 120%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.hero p {
  margin: 14px 0 0;
  max-width: 720px;
  color: var(--text-2);
  font-size: 16px;
  line-height: 1.6;
}

.hero .tags {
  display: flex; flex-wrap: wrap; gap: 8px;
  margin-top: 22px;
}

.tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 11px;
  border-radius: 999px;
  font-size: 12px;
  font-family: 'JetBrains Mono', monospace;
  background: rgba(255,255,255,0.04);
  border: 1px solid var(--glass-border);
  color: var(--text-2);
}

.tag .swatch {
  width: 6px; height: 6px; border-radius: 50%;
  background: var(--mint);
  box-shadow: 0 0 6px currentColor;
}
.tag.amber .swatch  { background: var(--amber); color: var(--amber); }
.tag.coral .swatch  { background: var(--coral); color: var(--coral); }
.tag.violet .swatch { background: var(--violet); color: var(--violet); }
.tag.cyan .swatch   { background: var(--cyan);  color: var(--cyan); }

/* ---------- Demo grid ---------- */

.grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
}

@media (min-width: 900px) {
  .grid { grid-template-columns: 1fr 1fr; }
  .grid > .demo.full { grid-column: 1 / -1; }
}

/* ---------- Demo card ---------- */

.demo {
  position: relative;
  padding: 24px 22px 22px;
  border-radius: var(--radius-lg);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  backdrop-filter: blur(28px) saturate(140%);
  -webkit-backdrop-filter: blur(28px) saturate(140%);
  box-shadow:
    0 20px 60px rgba(0,0,0,0.5),
    inset 0 1px 0 rgba(255,255,255,0.05);
  transition: border-color 240ms var(--ease-out), transform 240ms var(--ease-out);
  overflow: hidden;
}

.demo::before {
  /* Top edge highlight — the "liquid" sheen. */
  content: '';
  position: absolute;
  inset: 0 0 auto 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.22), transparent);
  pointer-events: none;
}

.demo:hover { border-color: var(--glass-border-strong); }

.demo-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 14px;
  margin-bottom: 4px;
}

.demo-title {
  margin: 0;
  font-size: 19px;
  font-weight: 600;
  letter-spacing: -0.015em;
  display: flex;
  align-items: center;
  gap: 10px;
}

.demo-title .num {
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  color: var(--text-3);
  padding: 4px 8px;
  border-radius: 6px;
  background: rgba(255,255,255,0.04);
  border: 1px solid var(--glass-border);
  font-weight: 500;
}

.demo-subtitle {
  margin: 4px 0 18px;
  color: var(--text-2);
  font-size: 13px;
  line-height: 1.5;
}

.demo-actions {
  display: flex;
  gap: 8px;
  flex-shrink: 0;
}

/* ---------- Buttons ---------- */

.btn {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  padding: 9px 14px;
  font-family: inherit;
  font-size: 13px;
  font-weight: 500;
  border-radius: 10px;
  border: 1px solid var(--glass-border);
  background: rgba(255,255,255,0.05);
  color: var(--text-1);
  cursor: pointer;
  transition: background 180ms var(--ease-out),
              border-color 180ms var(--ease-out),
              transform 120ms var(--ease-out);
  user-select: none;
  -webkit-user-select: none;
}

.btn:hover { background: var(--glass-bg-hover); border-color: var(--glass-border-strong); }
.btn:active { transform: scale(0.97); }
.btn:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 2px;
}
.btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  pointer-events: none;
}

.btn-primary {
  background: linear-gradient(135deg, var(--mint) 0%, #2bd498 100%);
  color: #001a10;
  border-color: rgba(57, 255, 176, 0.4);
  box-shadow: 0 0 0 1px rgba(57,255,176,0.18) inset, 0 8px 24px rgba(57,255,176,0.18);
}
.btn-primary:hover { filter: brightness(1.08); }

.btn-danger {
  background: linear-gradient(135deg, var(--coral) 0%, #d83a5d 100%);
  color: #1a0008;
  border-color: rgba(255, 92, 122, 0.4);
}
.btn-danger:hover { filter: brightness(1.08); }

.btn-ghost { background: transparent; }

.btn .icon {
  width: 14px; height: 14px;
}

/* ---------- Info panel (collapsible "What is this?") ---------- */

.info {
  margin-bottom: 16px;
  border-radius: var(--radius-md);
  background: rgba(255,255,255,0.025);
  border: 1px solid var(--glass-border);
  overflow: hidden;
}

.info summary {
  list-style: none;
  cursor: pointer;
  padding: 11px 14px;
  font-size: 13px;
  color: var(--text-2);
  display: flex;
  align-items: center;
  gap: 8px;
  transition: background 160ms var(--ease-out);
  -webkit-user-select: none;
  user-select: none;
}
.info summary::-webkit-details-marker { display: none; }
.info summary:hover { background: rgba(255,255,255,0.04); }

.info summary::before {
  content: '';
  width: 14px; height: 14px;
  background: currentColor;
  -webkit-mask: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='currentColor' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'><circle cx='12' cy='12' r='10'/><path d='M12 16v-4'/><path d='M12 8h.01'/></svg>") center / contain no-repeat;
  mask: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='currentColor' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'><circle cx='12' cy='12' r='10'/><path d='M12 16v-4'/><path d='M12 8h.01'/></svg>") center / contain no-repeat;
  color: var(--cyan);
}

.info-body {
  padding: 4px 16px 14px;
  color: var(--text-2);
  font-size: 13px;
  line-height: 1.6;
}
.info-body p { margin: 8px 0; }
.info-body strong { color: var(--text-1); font-weight: 600; }
.info-body code {
  font-family: 'JetBrains Mono', monospace;
  font-size: 12px;
  padding: 1px 6px;
  border-radius: 4px;
  background: rgba(255,255,255,0.07);
  color: var(--mint);
}

/* ---------- Stats / numbers ---------- */

.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 10px;
  margin-top: 14px;
}

.stat {
  padding: 12px 14px;
  border-radius: var(--radius-md);
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--glass-border);
}

.stat .label {
  font-size: 11px;
  color: var(--text-3);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.stat .value {
  font-family: 'JetBrains Mono', monospace;
  font-variant-numeric: tabular-nums;
  font-size: 20px;
  font-weight: 600;
  margin-top: 4px;
  letter-spacing: -0.01em;
}

.stat.good .value  { color: var(--mint); }
.stat.bad .value   { color: var(--coral); }
.stat.warn .value  { color: var(--amber); }
.stat.info .value  { color: var(--cyan); }

/* ---------- Progress / meter ---------- */

.meter {
  position: relative;
  height: 8px;
  border-radius: 999px;
  background: rgba(255,255,255,0.04);
  overflow: hidden;
  margin-top: 10px;
}

.meter > .fill {
  height: 100%;
  background: linear-gradient(90deg, var(--mint) 0%, var(--cyan) 100%);
  border-radius: 999px;
  transition: width 220ms var(--ease-out);
  box-shadow: 0 0 12px var(--mint);
}

.meter.bad > .fill { background: linear-gradient(90deg, var(--coral), var(--amber)); box-shadow: 0 0 12px var(--coral); }

/* ---------- Buffer slots (producer-consumer) ---------- */

.buffer {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  margin-top: 16px;
  padding: 14px;
  border-radius: var(--radius-md);
  background: rgba(0,0,0,0.25);
  border: 1px solid var(--glass-border);
}

.slot {
  width: 44px;
  height: 44px;
  border-radius: 10px;
  background: rgba(255,255,255,0.025);
  border: 1px dashed rgba(255,255,255,0.1);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'JetBrains Mono', monospace;
  font-size: 13px;
  color: var(--text-3);
  transition: all 180ms var(--ease-spring);
}

.slot.filled {
  background: linear-gradient(135deg, rgba(57,255,176,0.22), rgba(91,224,255,0.18));
  border: 1px solid rgba(57,255,176,0.45);
  color: #fff;
  box-shadow: 0 0 16px rgba(57,255,176,0.25), inset 0 1px 0 rgba(255,255,255,0.15);
  transform: translateY(-2px);
}

/* ---------- Lanes (readers-writers) ---------- */

.lanes {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-top: 16px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 12px;
}

.lane {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 8px 12px;
  border-radius: 10px;
  background: rgba(255,255,255,0.025);
  border: 1px solid var(--glass-border);
}

.lane .name {
  width: 48px;
  font-weight: 600;
  color: var(--text-1);
}

.lane .state {
  flex: 1;
  padding: 3px 10px;
  border-radius: 6px;
  font-size: 11px;
  text-align: center;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  background: rgba(255,255,255,0.04);
  color: var(--text-3);
  transition: all 180ms var(--ease-out);
}

.lane.idle .state    { background: rgba(255,255,255,0.04); color: var(--text-3); }
.lane.waiting .state { background: var(--amber-soft); color: var(--amber); border: 1px solid rgba(255,181,71,0.3); }
.lane.reading .state { background: var(--mint-soft); color: var(--mint); border: 1px solid rgba(57,255,176,0.3); }
.lane.writing .state { background: var(--coral-soft); color: var(--coral); border: 1px solid rgba(255,92,122,0.3); }

/* ---------- Code block ---------- */

.code {
  margin-top: 16px;
  padding: 16px;
  border-radius: var(--radius-md);
  background: rgba(0, 0, 0, 0.4);
  border: 1px solid var(--glass-border);
  font-family: 'JetBrains Mono', monospace;
  font-size: 12px;
  line-height: 1.7;
  color: var(--text-1);
  overflow-x: auto;
  white-space: pre;
  -webkit-overflow-scrolling: touch;
}

.code .kw  { color: #c792ea; }
.code .fn  { color: var(--cyan); }
.code .str { color: var(--mint); }
.code .num { color: var(--amber); }
.code .com { color: var(--text-3); font-style: italic; }
.code .ty  { color: var(--violet); }

/* ---------- Charts ---------- */

.chart-wrap {
  margin-top: 16px;
  padding: 14px;
  border-radius: var(--radius-md);
  background: rgba(0, 0, 0, 0.25);
  border: 1px solid var(--glass-border);
  height: 220px;
  position: relative;
}

/* ---------- Deadlock visualization ---------- */

.dl-grid {
  display: grid;
  grid-template-columns: 1fr 60px 1fr;
  align-items: center;
  gap: 14px;
  margin-top: 16px;
}

.dl-thread {
  padding: 16px;
  border-radius: var(--radius-md);
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--glass-border);
  text-align: center;
  transition: all 240ms var(--ease-out);
}

.dl-thread.holding {
  border-color: rgba(57,255,176,0.4);
  background: var(--mint-soft);
}

.dl-thread.waiting {
  border-color: rgba(255,181,71,0.4);
  background: var(--amber-soft);
}

.dl-thread.deadlocked {
  border-color: rgba(255,92,122,0.5);
  background: var(--coral-soft);
  animation: shake 320ms var(--ease-out);
}

.dl-thread .who {
  font-weight: 600;
  font-size: 14px;
}
.dl-thread .what {
  margin-top: 6px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  color: var(--text-2);
}

.dl-arrows {
  position: relative;
  height: 80px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 24px;
  color: var(--text-3);
  display: flex;
  align-items: center;
  justify-content: center;
}

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  25%      { transform: translateX(-4px); }
  75%      { transform: translateX(4px); }
}

/* ---------- Timeline (priority inversion) ---------- */

.timeline-wrap {
  margin-top: 16px;
  padding: 14px;
  border-radius: var(--radius-md);
  background: rgba(0, 0, 0, 0.3);
  border: 1px solid var(--glass-border);
}

.tl-row {
  display: grid;
  grid-template-columns: 64px 1fr;
  gap: 10px;
  align-items: center;
  margin: 6px 0;
}

.tl-label {
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  font-weight: 600;
  text-align: right;
  color: var(--text-2);
}

.tl-track {
  position: relative;
  height: 24px;
  border-radius: 6px;
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--glass-border);
  overflow: hidden;
}

.tl-block {
  position: absolute;
  top: 2px;
  bottom: 2px;
  border-radius: 4px;
  font-size: 10px;
  font-family: 'JetBrains Mono', monospace;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #001a10;
  font-weight: 600;
  white-space: nowrap;
}

.tl-block.low    { background: var(--violet); color: #0a0518; }
.tl-block.medium { background: var(--amber); color: #1a1100; }
.tl-block.high   { background: var(--mint); }

/* ---------- Banner ---------- */

.banner {
  margin-top: 14px;
  padding: 10px 14px;
  border-radius: var(--radius-md);
  background: var(--violet-soft);
  border: 1px solid rgba(139,124,255,0.3);
  font-size: 12px;
  color: var(--text-2);
  display: flex;
  align-items: center;
  gap: 10px;
  line-height: 1.5;
}

.banner::before {
  content: 'ℹ';
  font-size: 14px;
  color: var(--violet);
  flex-shrink: 0;
}

/* ---------- Footer ---------- */

.footer {
  margin-top: 60px;
  padding: 24px;
  text-align: center;
  font-size: 12px;
  color: var(--text-3);
  font-family: 'JetBrains Mono', monospace;
  letter-spacing: 0.04em;
  border-top: 1px solid var(--glass-border);
}

.footer a {
  color: var(--cyan);
  text-decoration: none;
}
.footer a:hover { text-decoration: underline; }

/* ---------- Phase pill ---------- */

.phase {
  display: inline-block;
  margin: 12px 0 0;
  padding: 5px 11px;
  border-radius: 999px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  background: var(--cyan);
  color: #001020;
  font-weight: 500;
  letter-spacing: 0.04em;
}

/* ---------- Empty state ---------- */

.empty {
  text-align: center;
  padding: 28px;
  color: var(--text-3);
  font-size: 13px;
  font-style: italic;
}

/* ---------- Mobile tweaks ---------- */

@media (max-width: 640px) {
  .hero { padding: 26px 18px; }
  .demo { padding: 18px 16px; backdrop-filter: blur(16px); -webkit-backdrop-filter: blur(16px); }
  .demo-header { flex-direction: column; align-items: stretch; }
  .demo-actions { width: 100%; }
  .demo-actions .btn { flex: 1; justify-content: center; }
  .stats { grid-template-columns: 1fr 1fr; }
  .slot { width: 38px; height: 38px; }
  .chart-wrap { height: 180px; }
  .dl-grid { grid-template-columns: 1fr; }
  .dl-arrows { display: none; }
}

/* ---------- Reduced motion ---------- */

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    transition-duration: 0.001ms !important;
  }
}

/* =========================================================================
   PRESENTATION SECTIONS — the whole "PowerPoint" lives in the page.
   ========================================================================= */

.section {
  scroll-margin-top: 90px;
  padding: 56px 0 8px;
}

.section-kicker {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 5px 12px;
  border-radius: 999px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--cyan);
  background: rgba(91,224,255,0.08);
  border: 1px solid rgba(91,224,255,0.22);
  margin-bottom: 14px;
}

.section-title {
  margin: 0 0 14px;
  font-size: clamp(26px, 3.4vw, 38px);
  font-weight: 600;
  letter-spacing: -0.02em;
  background: linear-gradient(180deg, #fff 0%, #aab4c8 130%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

.section-lead {
  margin: 0 0 28px;
  font-size: 16px;
  line-height: 1.7;
  color: var(--text-2);
  max-width: 780px;
}

.split {
  display: grid;
  grid-template-columns: 1fr;
  gap: 18px;
}
@media (min-width: 900px) {
  .split.two { grid-template-columns: 1fr 1fr; }
  .split.three { grid-template-columns: repeat(3, 1fr); }
}

.point {
  padding: 22px 22px 20px;
  border-radius: var(--radius-lg);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  backdrop-filter: blur(28px) saturate(140%);
  -webkit-backdrop-filter: blur(28px) saturate(140%);
  position: relative;
  overflow: hidden;
}
.point::before {
  content: '';
  position: absolute;
  inset: 0 0 auto 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.22), transparent);
  pointer-events: none;
}
.point h3 {
  margin: 0 0 6px;
  font-size: 18px;
  font-weight: 600;
  letter-spacing: -0.01em;
  display: flex; align-items: center; gap: 10px;
}
.point h3 .dot {
  width: 8px; height: 8px; border-radius: 50%;
  background: var(--mint);
  box-shadow: 0 0 8px var(--mint);
}
.point.amber  h3 .dot { background: var(--amber); box-shadow: 0 0 8px var(--amber); }
.point.coral  h3 .dot { background: var(--coral); box-shadow: 0 0 8px var(--coral); }
.point.violet h3 .dot { background: var(--violet); box-shadow: 0 0 8px var(--violet); }
.point.cyan   h3 .dot { background: var(--cyan); box-shadow: 0 0 8px var(--cyan); }
.point p {
  margin: 6px 0 0;
  font-size: 14px;
  line-height: 1.65;
  color: var(--text-2);
}
.point code {
  font-family: 'JetBrains Mono', monospace;
  font-size: 12.5px;
  padding: 1px 6px;
  border-radius: 4px;
  background: rgba(255,255,255,0.06);
  color: var(--mint);
}

/* Architecture diagram (CSS-only) */
.arch {
  display: grid;
  grid-template-columns: 1fr;
  gap: 16px;
  margin-top: 14px;
}
@media (min-width: 900px) {
  .arch { grid-template-columns: 1fr auto 1fr; align-items: center; }
}
.arch-box {
  padding: 22px;
  border-radius: var(--radius-lg);
  background: var(--glass-bg);
  border: 1px solid var(--glass-border);
  backdrop-filter: blur(20px);
}
.arch-box .label {
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  letter-spacing: 0.12em;
  color: var(--cyan);
  text-transform: uppercase;
}
.arch-box h4 {
  margin: 6px 0 10px;
  font-size: 18px;
  font-weight: 600;
}
.arch-box ul {
  margin: 0; padding-left: 18px;
  color: var(--text-2);
  font-size: 14px;
  line-height: 1.7;
}
.arch-arrow {
  text-align: center;
  font-family: 'JetBrains Mono', monospace;
  color: var(--cyan);
  font-size: 13px;
  letter-spacing: 0.1em;
}
.arch-arrow .line {
  display: block;
  height: 2px;
  background: linear-gradient(90deg, var(--mint), var(--cyan));
  border-radius: 1px;
  margin: 10px 0;
  box-shadow: 0 0 8px var(--cyan);
}

/* Numbered key list (concept summary) */
.keylist {
  display: grid;
  grid-template-columns: 1fr;
  gap: 12px;
  counter-reset: kl;
}
@media (min-width: 700px) {
  .keylist { grid-template-columns: 1fr 1fr; }
}
@media (min-width: 1100px) {
  .keylist { grid-template-columns: repeat(3, 1fr); }
}
.keylist li {
  position: relative;
  list-style: none;
  padding: 18px 18px 16px 56px;
  border-radius: var(--radius-md);
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--glass-border);
  counter-increment: kl;
}
.keylist li::before {
  content: counter(kl, decimal-leading-zero);
  position: absolute;
  left: 16px; top: 16px;
  font-family: 'JetBrains Mono', monospace;
  font-size: 13px;
  font-weight: 600;
  color: var(--cyan);
  letter-spacing: 0.05em;
}
.keylist b {
  display: block;
  font-size: 14px;
  font-weight: 600;
  color: var(--text-1);
  margin-bottom: 2px;
}
.keylist span {
  font-size: 13px;
  color: var(--text-2);
  line-height: 1.55;
}

/* Big block quote (motivation) */
.callout {
  margin: 22px 0 0;
  padding: 22px 24px;
  border-left: 3px solid var(--mint);
  background: linear-gradient(90deg, rgba(57,255,176,0.06), transparent 60%);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  font-size: 17px;
  line-height: 1.6;
  color: var(--text-1);
  font-weight: 500;
}

/* Conclusion grid */
.conclusion-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 16px;
  margin-top: 18px;
}
@media (min-width: 900px) {
  .conclusion-grid { grid-template-columns: 1fr 1fr; }
}

/* Repository pill */
.repo-card {
  margin-top: 28px;
  padding: 22px 24px;
  border-radius: var(--radius-lg);
  background: linear-gradient(135deg,
    rgba(57,255,176,0.08) 0%,
    rgba(91,224,255,0.06) 50%,
    rgba(139,124,255,0.05) 100%);
  border: 1px solid rgba(57,255,176,0.22);
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
  align-items: center;
  justify-content: space-between;
}
.repo-card .links {
  display: flex; flex-direction: column; gap: 6px;
}
.repo-card .links a {
  font-family: 'JetBrains Mono', monospace;
  font-size: 14px;
  color: var(--mint);
  text-decoration: none;
  border-bottom: 1px dashed rgba(57,255,176,0.4);
}
.repo-card .links a:hover {
  color: var(--cyan);
  border-color: var(--cyan);
}
.repo-card .meta {
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  letter-spacing: 0.14em;
  color: var(--text-3);
  text-transform: uppercase;
}

/* =========================================================================
   SIDE NAVIGATION — sticky on desktop, hidden on mobile.
   ========================================================================= */

.sidenav {
  position: fixed;
  top: 50%;
  transform: translateY(-50%);
  right: 16px;
  z-index: 30;
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 14px 12px;
  border-radius: 999px;
  background: rgba(10, 12, 19, 0.55);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border: 1px solid var(--glass-border);
}
.sidenav a {
  width: 10px; height: 10px;
  border-radius: 50%;
  background: rgba(255,255,255,0.18);
  display: block;
  position: relative;
  transition: background 200ms var(--ease-out), transform 200ms var(--ease-out);
}
.sidenav a:hover { background: var(--cyan); transform: scale(1.3); }
.sidenav a.active {
  background: var(--mint);
  box-shadow: 0 0 8px var(--mint);
}
.sidenav a span {
  position: absolute;
  right: 22px; top: 50%;
  transform: translateY(-50%);
  white-space: nowrap;
  font-family: 'JetBrains Mono', monospace;
  font-size: 11px;
  color: var(--text-1);
  background: rgba(10,12,19,0.85);
  border: 1px solid var(--glass-border);
  padding: 4px 8px;
  border-radius: 6px;
  opacity: 0;
  pointer-events: none;
  transition: opacity 160ms;
}
.sidenav a:hover span { opacity: 1; }

@media (max-width: 900px) { .sidenav { display: none; } }

/* Header (course banner) */
.course-banner {
  margin-top: 26px;
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  align-items: center;
  justify-content: space-between;
  padding: 16px 22px;
  border-radius: var(--radius-md);
  background: rgba(255,255,255,0.025);
  border: 1px solid var(--glass-border);
  font-family: 'JetBrains Mono', monospace;
  font-size: 12px;
  color: var(--text-2);
}
.course-banner .left { display: flex; gap: 22px; flex-wrap: wrap; }
.course-banner .left b { color: var(--mint); font-weight: 600; }
.course-banner .right { color: var(--text-3); }

/* =========================================================================
   "Show code" panel — collapsible source-code viewer per demo, with a
   REAL / SIMULATED tag so a reader can tell at a glance which demos run
   real OS threads.
   ========================================================================= */

.code-panel {
  margin-top: 14px;
  border-radius: var(--radius-md);
  background: rgba(0, 0, 0, 0.35);
  border: 1px solid var(--glass-border);
  overflow: hidden;
}
.code-panel summary {
  list-style: none;
  cursor: pointer;
  padding: 12px 14px;
  font-size: 13px;
  color: var(--text-2);
  display: flex;
  align-items: center;
  gap: 10px;
  transition: background 160ms var(--ease-out);
  -webkit-user-select: none; user-select: none;
}
.code-panel summary::-webkit-details-marker { display: none; }
.code-panel summary:hover { background: rgba(255,255,255,0.04); }
.code-panel summary::before {
  content: '';
  width: 14px; height: 14px;
  background: var(--mint);
  -webkit-mask: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='currentColor' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'><polyline points='16 18 22 12 16 6'/><polyline points='8 6 2 12 8 18'/></svg>") center / contain no-repeat;
  mask: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='currentColor' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'><polyline points='16 18 22 12 16 6'/><polyline points='8 6 2 12 8 18'/></svg>") center / contain no-repeat;
}
.code-panel summary .label { flex: 1; font-weight: 500; color: var(--text-1); }
.code-panel .code-tag {
  font-family: 'JetBrains Mono', monospace;
  font-size: 10px; letter-spacing: 0.12em;
  padding: 3px 9px; border-radius: 999px;
  text-transform: uppercase; font-weight: 600;
}
.code-panel .code-tag.real {
  background: rgba(57,255,176,0.14);
  border: 1px solid rgba(57,255,176,0.45);
  color: var(--mint);
}
.code-panel .code-tag.sim {
  background: rgba(139,124,255,0.14);
  border: 1px solid rgba(139,124,255,0.45);
  color: var(--violet);
}
.code-panel .code {
  margin: 0;
  border: none;
  border-radius: 0;
  border-top: 1px solid var(--glass-border);
}
.code-panel .code-note {
  padding: 10px 14px;
  font-size: 12px;
  color: var(--text-3);
  font-style: italic;
  border-top: 1px solid var(--glass-border);
  background: rgba(255,255,255,0.02);
}