:root {
  color-scheme: light;
  --bg: #ebebeb;
  --bg-soft: #f4f4f4;
  --surface: #fafafa;
  --surface-hover: #e4e4e4;
  --ink: #161616;
  --ink-secondary: #3a3a3a;
  --muted: #6a6a6a;
  --faint: #949494;
  --line: #d6d6d6;
  --line-strong: #bdbdbd;
  --focus: #1c1c1c;
  --accent-line: #2a2a2a;
  --mark-bg: #d0d0d0;
  --topbar-bg: rgba(235, 235, 235, 0.82);
  --search-bg: #fafafa;
  --panel: #f7f7f7;
  --panel-strong: #efefef;
  --step-idle: #cfcfcf;
  --radius: 10px;
  --radius-sm: 7px;
  --font: "Manrope", ui-sans-serif, system-ui, sans-serif;
  --page-width: 960px;
  --content-width: 720px;
}

[data-theme="dark"] {
  color-scheme: dark;
  --bg: #111111;
  --bg-soft: #171717;
  --surface: #1c1c1c;
  --surface-hover: #2a2a2a;
  --ink: #efefef;
  --ink-secondary: #c6c6c6;
  --muted: #989898;
  --faint: #6f6f6f;
  --line: #2a2a2a;
  --line-strong: #3d3d3d;
  --focus: #efefef;
  --accent-line: #d0d0d0;
  --mark-bg: #3a3a3a;
  --topbar-bg: rgba(17, 17, 17, 0.86);
  --search-bg: #1c1c1c;
  --panel: #191919;
  --panel-strong: #222222;
  --step-idle: #3a3a3a;
}

* {
  box-sizing: border-box;
}

html {
  min-height: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 72px;
}

body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(1200px 500px at 50% -10%, color-mix(in srgb, var(--ink) 4%, transparent), transparent 60%),
    var(--bg);
  color: var(--ink);
  font-family: var(--font);
  font-size: 15px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

button,
input,
select,
textarea {
  font: inherit;
}

a {
  color: inherit;
  text-decoration: none;
}

button {
  cursor: pointer;
}

/* ——— Top bar ——— */

.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  min-height: 52px;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  border-bottom: 1px solid var(--line);
  background: var(--topbar-bg);
  padding: 0 clamp(18px, 4vw, 40px);
  backdrop-filter: blur(18px) saturate(1.15);
  -webkit-backdrop-filter: blur(18px) saturate(1.15);
}

.topbar nav {
  display: flex;
  gap: 2px;
}

.topbar nav a {
  padding: 7px 12px;
  border-radius: 999px;
  color: var(--muted);
  font-size: 13px;
  font-weight: 600;
  transition: color 0.15s ease, background 0.15s ease;
}

.topbar nav a:hover {
  color: var(--ink);
  background: var(--surface-hover);
}

.topbar nav a[aria-current="page"] {
  color: var(--ink);
  background: var(--surface);
}

.topbar-end {
  display: flex;
  align-items: center;
  gap: 10px;
}

#entry-count {
  margin: 0;
  color: var(--faint);
  font-size: 12px;
  font-weight: 600;
  font-variant-numeric: tabular-nums;
}

.contribute-btn {
  display: inline-flex;
  align-items: center;
  min-height: 32px;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  background: #ffffff;
  color: #161616;
  padding: 0 12px;
  font-size: 12px;
  font-weight: 600;
  transition: background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}

.contribute-btn:hover {
  background: #f3f3f3;
  border-color: #b0b0b0;
  color: #161616;
  text-decoration: none;
}

[data-theme="light"] .contribute-btn {
  border-color: #1a1a1a;
  background: #1a1a1a;
  color: #ffffff;
}

[data-theme="light"] .contribute-btn:hover {
  border-color: #000000;
  background: #000000;
  color: #ffffff;
}

.theme-toggle {
  display: grid;
  place-items: center;
  width: 34px;
  height: 34px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--surface);
  color: var(--muted);
  transition: color 0.15s ease, border-color 0.15s ease, background 0.15s ease;
}

.theme-toggle:hover {
  color: var(--ink);
  border-color: var(--line-strong);
}

[data-theme="light"] .theme-icon-sun,
[data-theme="dark"] .theme-icon-moon {
  display: none;
}

.theme-icon {
  display: grid;
  place-items: center;
}

/* ——— Page ——— */

.page {
  width: min(var(--page-width), calc(100% - 36px));
  margin: 0 auto;
  padding: 0 0 100px;
}

.page.is-home {
  display: flex;
  flex-direction: column;
  min-height: calc(100vh - 52px);
}

.page.is-home .search-panel {
  flex: 1;
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding-bottom: 12vh;
  overflow: visible;
}

.page.is-article .search-panel,
.page.is-browse .search-panel {
  display: none;
}

/* ——— Search ——— */

.search-panel {
  padding-top: 28px;
}

.search-hero {
  display: none;
  text-align: center;
  margin-bottom: 28px;
}

.page.is-home:not(.has-query) .search-hero {
  display: block;
  animation: fadeUp 0.45s ease both;
}

.search-heading {
  display: flex;
  align-items: baseline;
  justify-content: center;
  flex-wrap: wrap;
  gap: 0.35em 0.55em;
  margin: 0 0 12px;
  line-height: 1.05;
}

.search-heading-title {
  font-family: "Times New Roman", Times, serif;
  font-size: clamp(2.2rem, 5.5vw, 3.25rem);
  font-weight: 400;
  letter-spacing: -0.03em;
  color: var(--ink);
}

.search-version {
  font-family: "IBM Plex Mono", ui-monospace, monospace;
  font-size: clamp(1.15rem, 2.8vw, 1.55rem);
  font-weight: 500;
  font-style: italic;
  letter-spacing: 0.04em;
  color: #9a9a9a;
  text-shadow: none;
  background: none;
  border-radius: 0;
  padding: 0;
}

[data-theme="dark"] .search-version {
  color: #8e8e8e;
}

[data-theme="light"] .search-version {
  color: #7a7a7a;
  text-shadow: none;
  background: none;
  padding: 0;
}

.search-sub {
  margin: 0 auto;
  width: max-content;
  max-width: min(100%, 52rem);
  color: var(--muted);
  font-size: 14px;
  font-weight: 500;
  line-height: 1.45;
  white-space: nowrap;
}

.search-sep-link {
  font-family: "Times New Roman", Times, serif;
  font-style: italic;
  font-weight: 400;
  color: var(--ink-secondary);
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-thickness: 1px;
}

.search-sep-link:hover {
  color: var(--ink);
}

.search-field-wrap {
  position: relative;
  max-width: 640px;
  margin: 0 auto;
  width: 100%;
  overflow: visible;
}

.page.is-home.has-query .search-field-wrap {
  max-width: none;
  margin: 0;
}

.search-field {
  position: relative;
  display: flex;
  align-items: center;
}

.search-suggestions {
  position: absolute;
  top: calc(100% + 6px);
  left: 0;
  right: 0;
  z-index: 8;
  display: grid;
  gap: 0;
  margin: 0;
  padding: 4px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: color-mix(in srgb, var(--surface) 92%, transparent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.06);
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transform: translateY(-3px);
  transition:
    opacity 0.16s ease,
    transform 0.16s ease,
    visibility 0.16s ease;
}

[data-theme="dark"] .search-suggestions {
  box-shadow: 0 10px 28px rgba(0, 0, 0, 0.35);
}

.search-suggestions.is-open {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
  transform: translateY(0);
}

.suggestions-label {
  margin: 0;
  padding: 4px 10px 2px;
  color: var(--faint);
  font-size: 10px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.suggestion-link {
  display: block;
  overflow: hidden;
  padding: 7px 10px;
  border-radius: 8px;
  color: var(--muted);
  font-size: 12.5px;
  font-weight: 500;
  letter-spacing: -0.01em;
  line-height: 1.3;
  text-overflow: ellipsis;
  white-space: nowrap;
  transition: color 0.12s ease, background 0.12s ease;
}

.suggestion-link:hover,
.suggestion-link:focus-visible {
  background: var(--surface-hover);
  color: var(--ink);
  outline: none;
}

.search-icon {
  position: absolute;
  left: 14px;
  color: var(--faint);
  pointer-events: none;
}

#search-input {
  width: 100%;
  min-height: 50px;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  background: var(--search-bg);
  color: var(--ink);
  outline: none;
  padding: 0 72px 0 42px;
  font-size: 15px;
  font-weight: 500;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

#search-input::placeholder {
  color: var(--faint);
  font-weight: 500;
}

#search-input:focus {
  border-color: var(--focus);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--focus) 10%, transparent);
}

.clear-btn {
  position: absolute;
  right: 8px;
  min-height: 32px;
  border: 0;
  border-radius: 999px;
  background: transparent;
  color: var(--muted);
  padding: 0 12px;
  font-size: 12px;
  font-weight: 600;
}

.clear-btn:hover {
  color: var(--ink);
  background: var(--surface-hover);
}

.clear-btn[hidden] {
  display: none;
}

.search-meta {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 28px;
  margin-top: 10px;
  color: var(--faint);
  font-size: 12px;
  font-weight: 600;
}

.page.is-home.has-query .search-meta {
  justify-content: flex-start;
}

/* ——— View ——— */

.view {
  padding-top: 8px;
}

.page.is-article .view,
.page.is-browse .view {
  padding-top: 32px;
}

.view:empty {
  display: none;
}

/* ——— Results ——— */

.results {
  display: grid;
  animation: fadeUp 0.28s ease both;
}

.result-link {
  display: block;
  padding: 13px 2px;
  border-bottom: 1px solid var(--line);
  font-size: 15px;
  font-weight: 600;
  letter-spacing: -0.02em;
  color: var(--ink);
}

.result-link:hover {
  color: var(--ink-secondary);
}

.empty {
  padding: 48px 0;
  color: var(--muted);
  font-size: 14px;
  text-align: center;
  font-weight: 500;
}

.empty a {
  color: var(--ink);
  text-decoration: underline;
  text-underline-offset: 3px;
}

/* ——— Browse ——— */

.browse-header {
  margin-bottom: 28px;
}

.browse-header h1,
.article-title {
  margin: 0;
  font-size: clamp(1.7rem, 3.8vw, 2.35rem);
  font-weight: 700;
  letter-spacing: -0.035em;
  line-height: 1.15;
}

.browse-header p {
  margin: 8px 0 0;
  color: var(--muted);
  font-size: 14px;
  font-weight: 500;
}

.browse {
  display: grid;
}

.alpha-group {
  display: grid;
  grid-template-columns: 36px 1fr;
  gap: 18px;
  border-top: 1px solid var(--line);
  padding: 18px 0;
}

.alpha-letter {
  color: var(--faint);
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.03em;
}

.alpha-list {
  display: grid;
  gap: 1px;
}

.browse-link {
  display: block;
  padding: 7px 0;
  font-size: 14px;
  font-weight: 500;
  color: var(--ink-secondary);
  letter-spacing: -0.01em;
}

.browse-link:hover {
  color: var(--ink);
}

/* ——— Article ——— */

.article {
  display: grid;
  gap: 0;
}

.article-header {
  margin-bottom: 22px;
}

.article-toolbar {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px 18px;
  margin-top: 16px;
}

.level-switcher {
  display: inline-flex;
  padding: 3px;
  border-radius: 999px;
  background: var(--panel-strong);
  gap: 2px;
}

.level-button {
  min-height: 32px;
  border: 0;
  border-radius: 999px;
  background: transparent;
  color: var(--muted);
  padding: 0 13px;
  font-size: 12px;
  font-weight: 600;
  transition: color 0.15s ease, background 0.15s ease;
}

.level-button:hover {
  color: var(--ink);
}

.level-button.active {
  background: var(--ink);
  color: var(--bg);
}

.article-meta-inline {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 6px 12px;
  color: var(--muted);
  font-size: 12px;
  font-weight: 600;
}

.meta-sep {
  color: var(--line-strong);
}

.source-link {
  color: var(--ink);
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-thickness: 1px;
}

/* Structure map — the pedagogical spine */

.structure-map {
  position: sticky;
  top: 52px;
  z-index: 12;
  margin: 0 0 28px;
  padding: 12px 0 14px;
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.structure-steps {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  list-style: none;
  margin: 0;
  padding: 0;
}

.structure-step {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  min-height: 34px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: var(--surface);
  color: var(--muted);
  padding: 0 12px 0 8px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: -0.01em;
  transition: color 0.15s ease, border-color 0.15s ease, background 0.15s ease;
}

.structure-step:hover {
  color: var(--ink);
  border-color: var(--line-strong);
}

.structure-step.is-active {
  color: var(--ink);
  border-color: var(--ink);
  background: var(--surface);
}

.structure-num {
  display: grid;
  place-items: center;
  width: 20px;
  height: 20px;
  border-radius: 999px;
  background: var(--panel-strong);
  color: var(--faint);
  font-size: 10px;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}

.structure-step.is-active .structure-num {
  background: var(--ink);
  color: var(--bg);
}

/* Article flow */

.article-flow {
  display: grid;
  gap: 18px;
  max-width: var(--content-width);
}

.block {
  scroll-margin-top: 140px;
}

.block-head {
  display: flex;
  align-items: baseline;
  gap: 10px;
  margin-bottom: 12px;
}

.block-index {
  color: var(--faint);
  font-size: 12px;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.04em;
}

.block-title {
  margin: 0;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--ink);
}

/* 01 Overview — open prose, no box */
.block-overview {
  padding: 4px 0 8px;
}

.block-overview .prose {
  margin: 0;
  font-size: 17.5px;
  font-weight: 500;
  line-height: 1.7;
  letter-spacing: -0.015em;
  color: var(--ink-secondary);
}

.block-overview .prose + .prose {
  margin-top: 1em;
}

/* 02 Key ideas — numbered idea stack */
.block-ideas {
  padding: 20px 22px;
  border-radius: var(--radius);
  background: var(--panel);
}

.idea-list {
  display: grid;
  gap: 14px;
  margin: 0;
  padding: 0;
  list-style: none;
  counter-reset: idea;
}

.idea-list li {
  display: grid;
  grid-template-columns: 28px minmax(0, 1fr);
  gap: 12px;
  align-items: start;
  font-size: 15px;
  font-weight: 500;
  line-height: 1.55;
  letter-spacing: -0.01em;
  color: var(--ink-secondary);
  counter-increment: idea;
}

.idea-list li::before {
  content: counter(idea);
  display: grid;
  place-items: center;
  width: 28px;
  height: 28px;
  border-radius: 999px;
  background: var(--surface);
  color: var(--muted);
  font-size: 12px;
  font-weight: 700;
  line-height: 1;
}

.idea-list .item-text,
.question-list .item-text {
  min-width: 0;
}

/* 03 Terms — definition pairs */
.block-terms {
  padding: 20px 22px;
  border-radius: var(--radius);
  background: var(--surface);
  border: 1px solid var(--line);
}

.terms {
  display: grid;
  gap: 16px;
}

.term {
  display: grid;
  gap: 4px;
  padding-top: 14px;
  border-top: 1px solid var(--line);
}

.term:first-child {
  padding-top: 0;
  border-top: 0;
}

.term strong {
  font-size: 14px;
  font-weight: 700;
  letter-spacing: -0.015em;
  color: var(--ink);
}

.term p {
  margin: 0;
  font-size: 14px;
  font-weight: 500;
  line-height: 1.55;
  color: var(--muted);
}

/* 04 Example — accent rail */
.block-example {
  padding: 20px 22px 20px 26px;
  border-radius: var(--radius);
  background: var(--panel);
  border-left: 3px solid var(--accent-line);
}

.block-example .prose {
  margin: 0;
  font-size: 15.5px;
  font-weight: 500;
  line-height: 1.65;
  letter-spacing: -0.01em;
  color: var(--ink-secondary);
}

/* 05 Why it matters — statement */
.block-matters {
  padding: 24px 26px;
  border-radius: var(--radius);
  background: var(--ink);
  color: var(--bg);
}

.block-matters .block-index,
.block-matters .block-title {
  color: color-mix(in srgb, var(--bg) 55%, transparent);
}

.block-matters .block-title {
  color: color-mix(in srgb, var(--bg) 82%, transparent);
}

.block-matters .prose {
  margin: 0;
  font-size: 16px;
  font-weight: 500;
  line-height: 1.6;
  letter-spacing: -0.015em;
  color: var(--bg);
}

/* 06 Questions — prompt list */
.block-questions {
  padding: 20px 22px;
  border-radius: var(--radius);
  border: 1px dashed var(--line-strong);
  background: transparent;
}

.question-list {
  display: grid;
  gap: 12px;
  margin: 0;
  padding: 0;
  list-style: none;
  counter-reset: q;
}

.question-list li {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  gap: 10px;
  align-items: baseline;
  font-size: 15px;
  font-weight: 500;
  line-height: 1.5;
  letter-spacing: -0.01em;
  color: var(--ink-secondary);
  counter-increment: q;
}

.question-list li::before {
  content: "Q" counter(q);
  color: var(--faint);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.04em;
}

mark,
mark.search-hit {
  margin: 0;
  padding: 0;
  border-radius: 0.12em;
  background: var(--mark-bg);
  color: inherit;
  font: inherit;
  font-weight: inherit;
  font-style: inherit;
  letter-spacing: inherit;
  box-decoration-break: clone;
  -webkit-box-decoration-break: clone;
}

@keyframes fadeUp {
  from {
    opacity: 0;
    transform: translateY(6px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ——— Responsive ——— */

@media (max-width: 720px) {
  .page {
    width: calc(100% - 28px);
  }

  #entry-count {
    display: none;
  }

  .search-sub {
    width: auto;
    max-width: 22rem;
    white-space: normal;
  }

  .structure-map {
    top: 52px;
    margin-left: -14px;
    margin-right: -14px;
    padding-left: 14px;
    padding-right: 14px;
  }

  .structure-steps {
    flex-wrap: nowrap;
    overflow-x: auto;
    padding-bottom: 4px;
    scrollbar-width: none;
  }

  .structure-steps::-webkit-scrollbar {
    display: none;
  }

  .structure-step {
    flex: 0 0 auto;
  }

  .block-overview .prose {
    font-size: 16.5px;
  }

  .block-ideas,
  .block-terms,
  .block-example,
  .block-matters,
  .block-questions {
    padding-left: 16px;
    padding-right: 16px;
  }

  .level-switcher {
    width: 100%;
  }

  .level-button {
    flex: 1;
  }

  .alpha-group {
    grid-template-columns: 1fr;
    gap: 6px;
  }
}