:root {
  color-scheme: light;
  --bg: #07111d;
  --bg-deep: #020409;
  --panel: rgba(13, 20, 31, 0.82);
  --panel-strong: rgba(18, 27, 41, 0.96);
  --text: #eef3f8;
  --muted: #8ea0b6;
  --line: rgba(164, 188, 214, 0.18);
  --line-strong: rgba(164, 188, 214, 0.3);
  --accent: #d6e7f7;
  --accent-strong: #f6fbff;
  --chip: rgba(30, 43, 60, 0.9);
  --chip-active: #90a8c2;
  --chip-soft: rgba(255, 255, 255, 0.05);
  --shadow: 0 28px 76px rgba(0, 0, 0, 0.42);
  --shadow-soft: 0 12px 30px rgba(0, 0, 0, 0.22);
  --radius: 24px;
  --radius-sm: 18px;
  --focus: rgba(214, 231, 247, 0.28);
}

* {
  box-sizing: border-box;
}

html {
  min-height: 100%;
  background:
    radial-gradient(circle at 50% 2%, rgba(206, 236, 255, 0.18), transparent 24%),
    radial-gradient(circle at 16% 8%, rgba(255, 255, 255, 0.08), transparent 18%),
    linear-gradient(180deg, #0d1a2d 0%, var(--bg) 34%, var(--bg-deep) 100%);
}

body {
  margin: 0;
  min-height: 100vh;
  color: var(--text);
  font-family:
    "Inter",
    "Segoe UI",
    "Helvetica Neue",
    Arial,
    system-ui,
    sans-serif;
  font-size: 16px;
  line-height: 1.62;
  background:
    linear-gradient(90deg, rgba(150, 181, 214, 0.07) 1px, transparent 1px) 0 0 / 42px 42px,
    linear-gradient(180deg, rgba(150, 181, 214, 0.07) 1px, transparent 1px) 0 0 / 42px 42px;
  background-attachment: fixed;
}

a {
  color: inherit;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.18em;
}

.shell {
  width: min(1120px, calc(100vw - 32px));
  margin: 0 auto;
  padding: 28px 0 56px;
}

.site-header {
  position: relative;
  padding: 16px 6px 24px;
}

.site-header--compact {
  padding-bottom: 14px;
}

.site-header::after {
  content: "";
  display: block;
  width: min(180px, 32vw);
  height: 1px;
  margin-top: 18px;
  background: linear-gradient(90deg, rgba(214, 231, 247, 0.48), transparent);
}

.eyebrow {
  margin: 0 0 10px;
  color: var(--muted);
  font-size: 0.9rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.site-header h1 {
  margin: 0;
  font-size: clamp(2.15rem, 5vw, 4.4rem);
  line-height: 0.94;
  letter-spacing: -0.05em;
}

.lede {
  max-width: 60ch;
  margin: 14px 0 0;
  color: var(--muted);
  font-size: 1.02rem;
  line-height: 1.65;
}

.panel {
  display: grid;
  gap: 22px;
}

.toolbar,
.chapters,
.chapter-page {
  position: relative;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  backdrop-filter: blur(14px) saturate(115%);
  -webkit-backdrop-filter: blur(14px) saturate(115%);
}

.toolbar::before,
.chapters::before,
.chapter-page::before {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: inherit;
  pointer-events: none;
  background: linear-gradient(180deg, rgba(255, 255, 255, 0.07), transparent 22%);
}

.toolbar,
.chapters {
  padding: 22px;
}

.toolbar__title,
.chapters__title {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 16px;
}

.toolbar h2,
.chapters h2,
.chapter-page h2 {
  margin: 0;
  font-size: 1.15rem;
  letter-spacing: -0.03em;
}

.toolbar p,
.chapters p {
  margin: 0;
  color: var(--muted);
  font-size: 0.95rem;
}

.tag-filters {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.tag-chip,
.chapter-nav__link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  min-height: 38px;
  padding: 0 14px;
  border: 1px solid transparent;
  border-radius: 999px;
  background: var(--chip);
  color: var(--accent-strong);
  font: inherit;
  font-size: 0.95rem;
  line-height: 1;
  cursor: pointer;
  box-shadow: var(--shadow-soft);
  transition:
    transform 120ms ease,
    background-color 120ms ease,
    border-color 120ms ease,
    box-shadow 120ms ease;
}

.tag-chip:hover,
.chapter-nav__link:hover {
  border-color: rgba(214, 231, 247, 0.22);
  transform: translateY(-1px);
}

.tag-chip[aria-pressed="true"] {
  background: var(--chip-active);
  border-color: rgba(214, 231, 247, 0.35);
  color: #0d1622;
}

.tag-chip--clear {
  background: var(--chip-soft);
  border-color: var(--line);
}

.chapter-list {
  display: grid;
  gap: 16px;
}

.chapter-card {
  display: grid;
  gap: 14px;
  padding: 20px 20px 18px;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background:
    linear-gradient(180deg, rgba(20, 31, 46, 0.88), rgba(10, 17, 27, 0.74)),
    rgba(255, 255, 255, 0.04);
  box-shadow: var(--shadow-soft);
}

.chapter-card__top {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 10px 16px;
}

.chapter-card__title {
  margin: 0;
  font-size: 1.2rem;
  line-height: 1.1;
}

.chapter-card__title a {
  text-decoration: none;
}

.chapter-card__title a:hover {
  text-decoration: underline;
  color: var(--accent);
}

.chapter-card__meta {
  color: var(--muted);
  font-size: 0.95rem;
  letter-spacing: 0.02em;
}

.chapter-card__summary {
  margin: 0;
  color: var(--text);
  font-size: 1.05rem;
  line-height: 1.72;
}

.chapter-card__tags {
  display: flex;
  flex-wrap: wrap;
  gap: 9px;
}

.chapter-card__tag {
  min-height: 32px;
  padding: 0 11px;
  border: 1px solid rgba(164, 188, 214, 0.15);
  border-radius: 999px;
  background: rgba(37, 52, 70, 0.9);
  color: var(--accent-strong);
  font: inherit;
  font-size: 0.92rem;
  cursor: pointer;
  transition:
    transform 120ms ease,
    background-color 120ms ease,
    border-color 120ms ease;
}

.chapter-card__tag:hover,
.chapter-page__tag:hover {
  text-decoration: underline;
  transform: translateY(-1px);
}

.empty-state {
  margin: 14px 2px 0;
  color: var(--muted);
  font-size: 0.98rem;
  line-height: 1.6;
}

.chapter-page {
  padding: 24px;
}

.chapter-page__tags {
  display: flex;
  flex-wrap: wrap;
  gap: 9px;
  margin-bottom: 18px;
}

.chapter-page__intro {
  max-width: 75ch;
  margin: 0 0 18px;
  padding: 14px 16px 14px 18px;
  border-left: 3px solid rgba(214, 231, 247, 0.28);
  border-radius: 0 16px 16px 0;
  background: linear-gradient(90deg, rgba(18, 28, 42, 0.92), rgba(18, 28, 42, 0.54));
  color: var(--muted);
  font-size: 1.08rem;
  line-height: 1.78;
  font-style: italic;
}

.chapter-page__video {
  margin: 0 0 24px;
  border-radius: 20px;
  overflow: hidden;
  background:
    radial-gradient(circle at 50% 0%, rgba(206, 236, 255, 0.14), transparent 42%),
    #05070c;
  box-shadow:
    inset 0 0 0 1px rgba(206, 236, 255, 0.08),
    0 18px 44px rgba(0, 0, 0, 0.5);
  aspect-ratio: 16 / 9;
}

.chapter-page__video-media {
  display: block;
  width: 100%;
  height: 100%;
  border: 0;
}

.chapter-page__text {
  display: grid;
  gap: 16px;
  margin-bottom: 24px;
  padding-top: 4px;
}

.chapter-page__text-title {
  margin: 4px 0 0;
  font-size: 1.18rem;
  line-height: 1.2;
  letter-spacing: -0.03em;
}

.chapter-page__text-paragraph {
  margin: 0;
  color: var(--text);
  font-size: 1.12rem;
  line-height: 1.88;
  white-space: pre-wrap;
}

.chapter-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.chapter-page__tag {
  min-height: 34px;
  padding: 0 12px;
  border: 1px solid rgba(164, 188, 214, 0.15);
  border-radius: 999px;
  background: rgba(37, 52, 70, 0.9);
  color: var(--accent-strong);
  font: inherit;
  font-size: 0.92rem;
  cursor: pointer;
  transition:
    transform 120ms ease,
    background-color 120ms ease,
    border-color 120ms ease;
}

.chapter-nav__link[aria-disabled="true"] {
  pointer-events: none;
  opacity: 0.42;
}

.chapter-page__tag:focus-visible,
.tag-chip:focus-visible,
.chapter-card__tag:focus-visible,
.chapter-nav__link:focus-visible,
.chapter-card__title a:focus-visible,
.eyebrow a:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
}

@media (prefers-reduced-motion: reduce) {
  .tag-chip,
  .chapter-nav__link,
  .chapter-card__tag,
  .chapter-page__tag {
    transition: none;
  }
}

@media (max-width: 720px) {
  .shell {
    width: min(100vw - 20px, 1100px);
    padding-top: 20px;
  }

  .toolbar__title,
  .chapters__title {
    align-items: flex-start;
    flex-direction: column;
  }

  .chapter-page {
    padding: 20px;
  }

  .toolbar,
  .chapters {
    padding: 18px;
  }

  .chapter-card {
    padding: 18px 16px 16px;
  }

  .chapter-page__intro {
    padding: 13px 14px 13px 16px;
  }
}