:root {
  color-scheme: light;
  --bg: #f7f8fb;
  --paper: #ffffff;
  --ink: #171820;
  --muted: #666b78;
  --faint: #989eaa;
  --line: #e7e9ef;
  --line-strong: #d8dbe4;
  --accent: #6157e7;
  --accent-soft: #eeecff;
  --accent-2: #21a38b;
  --danger: #c74747;
  --warning: #9d6a0f;
  --shadow: 0 18px 60px rgba(26, 28, 38, .08);
  --radius: 18px;
  --content: 1180px;
  --reading: 760px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  -webkit-font-smoothing: antialiased;
}
button, input, textarea, select { font: inherit; }
button, a { -webkit-tap-highlight-color: transparent; }
a { color: inherit; text-decoration: none; }
img { display: block; max-width: 100%; }

::selection { background: #dcd8ff; color: #12131a; }

.topbar {
  position: sticky;
  z-index: 40;
  top: 0;
  height: 68px;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 24px;
  padding: 0 max(24px, calc((100vw - var(--content)) / 2));
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(18px);
  border-bottom: 1px solid color-mix(in srgb, var(--line) 78%, transparent);
}
.brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 750; letter-spacing: -.02em; width: fit-content; }
.brand-mark { width: 24px; height: 24px; position: relative; display: inline-block; }
.brand-mark span { position: absolute; width: 7px; height: 7px; border-radius: 50%; background: var(--accent); }
.brand-mark span:nth-child(1) { left: 1px; top: 8px; }
.brand-mark span:nth-child(2) { right: 1px; top: 2px; }
.brand-mark span:nth-child(3) { right: 2px; bottom: 1px; }
.brand-mark::before, .brand-mark::after { content: ""; position: absolute; height: 1.5px; background: var(--accent); transform-origin: left center; left: 6px; top: 11px; width: 14px; }
.brand-mark::before { transform: rotate(-28deg); }
.brand-mark::after { transform: rotate(27deg); }
.topnav { display: flex; align-items: center; gap: 6px; }
.topnav a { padding: 8px 12px; border-radius: 999px; color: var(--muted); font-size: 14px; font-weight: 620; transition: .18s ease; }
.topnav a:hover, .topnav a.active { background: var(--paper); color: var(--ink); box-shadow: 0 1px 0 rgba(0,0,0,.04); }
.account-slot { justify-self: end; }
.account-button, .button, .icon-button {
  border: 0;
  cursor: pointer;
  transition: transform .16s ease, background .16s ease, color .16s ease, box-shadow .16s ease;
}
.account-button:hover, .button:hover, .icon-button:hover { transform: translateY(-1px); }
.account-button { display: inline-flex; align-items: center; gap: 9px; background: var(--paper); border: 1px solid var(--line); border-radius: 999px; padding: 7px 11px 7px 8px; color: var(--ink); font-size: 13px; font-weight: 650; }
.avatar { width: 26px; height: 26px; border-radius: 50%; object-fit: cover; background: var(--accent-soft); display: grid; place-items: center; font-weight: 800; color: var(--accent); }

#app { min-height: calc(100vh - 132px); }
.page { width: min(var(--content), calc(100% - 48px)); margin: 0 auto; padding: 54px 0 80px; }
.page-narrow { width: min(900px, calc(100% - 48px)); }

.eyebrow { display: inline-flex; align-items: center; gap: 8px; text-transform: uppercase; letter-spacing: .12em; font-size: 11px; font-weight: 800; color: var(--accent); }
.eyebrow::before { content: ""; width: 20px; height: 1px; background: currentColor; }
.display { margin: 14px 0 18px; max-width: 920px; font-size: clamp(44px, 7vw, 86px); line-height: .96; letter-spacing: -.065em; font-weight: 780; }
.lede { max-width: 760px; margin: 0; font-size: clamp(18px, 2vw, 22px); line-height: 1.55; color: var(--muted); }
.hero { padding: 42px 0 64px; }
.hero-actions { display: flex; align-items: center; flex-wrap: wrap; gap: 12px; margin-top: 28px; }

.searchbar { position: relative; width: min(560px, 100%); }
.searchbar input { width: 100%; height: 48px; border: 1px solid var(--line-strong); border-radius: 14px; background: var(--paper); padding: 0 48px 0 16px; outline: none; color: var(--ink); box-shadow: 0 8px 24px rgba(26, 28, 38, .04); }
.searchbar input:focus { border-color: #b8b3f8; box-shadow: 0 0 0 4px var(--accent-soft); }
.searchbar kbd { position: absolute; right: 11px; top: 11px; border: 1px solid var(--line); border-bottom-width: 2px; border-radius: 7px; background: var(--bg); color: var(--faint); font-size: 11px; padding: 4px 6px; }

.button { min-height: 42px; border-radius: 11px; padding: 0 15px; background: var(--ink); color: white; font-size: 14px; font-weight: 700; display: inline-flex; align-items: center; justify-content: center; gap: 8px; }
.button.secondary { color: var(--ink); background: var(--paper); border: 1px solid var(--line); }
.button.ghost { color: var(--muted); background: transparent; }
.button.accent { background: var(--accent); }
.button.danger { background: #fff1f1; color: var(--danger); }
.button:disabled { cursor: not-allowed; opacity: .5; transform: none; }

.section-head { display: flex; justify-content: space-between; align-items: end; gap: 20px; margin: 18px 0 24px; }
.section-head h2 { margin: 0; font-size: 25px; letter-spacing: -.035em; }
.section-head p { margin: 5px 0 0; color: var(--muted); }
.section-rule { border: 0; border-top: 1px solid var(--line); margin: 48px 0; }

.course-grid { display: grid; grid-template-columns: repeat(12, 1fr); gap: 22px; }
.course-card { grid-column: span 6; min-height: 260px; background: var(--paper); border-radius: 24px; padding: 26px; box-shadow: 0 1px 0 rgba(20,21,28,.04), 0 12px 40px rgba(20,21,28,.045); position: relative; overflow: hidden; transition: transform .22s ease, box-shadow .22s ease; }
.course-card:hover { transform: translateY(-4px); box-shadow: var(--shadow); }
.course-card::after { content: ""; position: absolute; width: 190px; height: 190px; border-radius: 50%; right: -80px; top: -80px; background: radial-gradient(circle at 40% 40%, color-mix(in srgb, var(--card-accent, var(--accent)) 34%, white), transparent 70%); opacity: .62; pointer-events: none; }
.course-meta { display: flex; align-items: center; flex-wrap: wrap; gap: 8px 14px; font-size: 12px; color: var(--muted); }
.course-meta strong { color: var(--ink); }
.course-card h3 { max-width: 520px; margin: 28px 0 10px; font-size: clamp(26px, 3vw, 38px); line-height: 1.02; letter-spacing: -.045em; }
.course-card p { max-width: 520px; margin: 0; color: var(--muted); line-height: 1.58; }
.course-footer { position: absolute; left: 26px; right: 26px; bottom: 23px; display: flex; align-items: center; justify-content: space-between; gap: 12px; }
.tags { display: flex; gap: 7px; flex-wrap: wrap; }
.tag { display: inline-flex; align-items: center; min-height: 26px; padding: 0 9px; border-radius: 999px; background: var(--bg); color: var(--muted); font-size: 11px; font-weight: 700; }
.rating-inline { font-size: 12px; font-weight: 700; white-space: nowrap; }
.star { color: #d69a13; }

.micro-features { display: grid; grid-template-columns: repeat(3, 1fr); gap: 34px; padding: 34px 0 6px; }
.micro-feature { padding-top: 16px; border-top: 1px solid var(--line); }
.micro-feature .index { font-variant-numeric: tabular-nums; font-size: 12px; color: var(--faint); }
.micro-feature h3 { margin: 18px 0 7px; font-size: 17px; letter-spacing: -.02em; }
.micro-feature p { margin: 0; color: var(--muted); line-height: 1.55; font-size: 14px; }

.empty-state { padding: 72px 0; text-align: center; color: var(--muted); }
.empty-state h2 { color: var(--ink); font-size: 26px; margin-bottom: 8px; }

.course-hero { display: grid; grid-template-columns: 1.3fr .7fr; gap: 54px; align-items: end; padding-bottom: 44px; border-bottom: 1px solid var(--line); }
.course-hero h1 { margin: 13px 0 16px; font-size: clamp(42px, 6vw, 76px); line-height: .98; letter-spacing: -.06em; }
.course-hero .summary { font-size: 18px; line-height: 1.58; color: var(--muted); max-width: 720px; }
.course-statline { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px; }
.stat { padding-top: 12px; border-top: 1px solid var(--line); }
.stat strong { display: block; font-size: 22px; letter-spacing: -.03em; }
.stat span { color: var(--muted); font-size: 12px; }
.progress-track { height: 5px; border-radius: 999px; background: #e8e9ef; overflow: hidden; margin-top: 18px; }
.progress-track span { display: block; height: 100%; width: var(--progress, 0%); background: var(--accent); border-radius: inherit; transition: width .3s ease; }

.course-layout { display: grid; grid-template-columns: 270px minmax(0, 1fr); gap: 58px; padding-top: 44px; }
.topic-rail { position: sticky; top: 98px; align-self: start; max-height: calc(100vh - 120px); overflow: auto; padding-right: 4px; }
.module-group + .module-group { margin-top: 28px; }
.module-title { margin: 0 0 8px; text-transform: uppercase; font-size: 10px; letter-spacing: .12em; color: var(--faint); font-weight: 800; }
.topic-link { width: 100%; display: grid; grid-template-columns: 24px 1fr; gap: 9px; align-items: start; padding: 8px 8px 8px 0; color: var(--muted); font-size: 13px; line-height: 1.35; border-radius: 9px; transition: .15s ease; }
.topic-link:hover { color: var(--ink); transform: translateX(3px); }
.topic-link.active { color: var(--ink); font-weight: 700; }
.topic-num { color: var(--faint); font-variant-numeric: tabular-nums; }
.topic-link.done .topic-num { color: var(--accent-2); }

.reader { max-width: var(--reading); min-width: 0; }
.reader-header { margin-bottom: 44px; }
.reader-kicker { display: flex; gap: 9px; align-items: center; color: var(--muted); font-size: 12px; }
.reader h2.topic-title { font-size: clamp(38px, 5vw, 62px); line-height: 1.02; letter-spacing: -.055em; margin: 12px 0 16px; }
.topic-summary { margin: 0; font-size: 20px; line-height: 1.58; color: var(--muted); }
.learning-goals { margin: 28px 0 0; padding: 0; list-style: none; display: grid; gap: 8px; }
.learning-goals li { position: relative; padding-left: 22px; line-height: 1.5; font-size: 14px; color: #40434d; }
.learning-goals li::before { content: "↳"; position: absolute; left: 0; color: var(--accent); font-weight: 800; }

.lesson-section { margin: 0 0 42px; }
.lesson-section h3 { margin: 0 0 13px; font-size: 23px; letter-spacing: -.03em; }
.lesson-section h4 { margin: 0 0 10px; font-size: 16px; }
.lesson-section p, .lesson-section li { font-family: Georgia, "Times New Roman", serif; font-size: 18px; line-height: 1.72; color: #33353d; }
.lesson-section p { margin: 0 0 16px; }
.lesson-section ul, .lesson-section ol { padding-left: 24px; }
.lesson-section li + li { margin-top: 8px; }
.lesson-lead { padding-left: 20px; border-left: 3px solid var(--accent); }
.lesson-lead p { font-size: 21px; line-height: 1.65; color: #242631; }
.callout { margin: 40px 0; padding: 22px 24px; background: var(--accent-soft); border-radius: 18px; }
.callout[data-tone="warning"] { background: #fff7e9; }
.callout[data-tone="success"] { background: #eaf8f4; }
.callout h3, .callout h4 { margin-top: 0; }
.callout p:last-child { margin-bottom: 0; }
.formula { margin: 28px 0; padding: 24px 10px; text-align: center; overflow-x: auto; border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.formula code { font-family: "SFMono-Regular", Consolas, monospace; color: var(--ink); }
.lesson-image { margin: 34px 0; }
.lesson-image img { width: 100%; border-radius: 16px; background: white; }
.lesson-image figcaption { margin-top: 9px; color: var(--muted); font-size: 12px; line-height: 1.5; }

.flow-diagram { margin: 30px 0 40px; display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.flow-node { min-height: 60px; display: grid; place-items: center; text-align: center; padding: 12px 15px; background: var(--paper); border: 1px solid var(--line); border-radius: 14px; font-weight: 720; font-size: 13px; box-shadow: 0 6px 22px rgba(20,21,28,.04); }
.flow-arrow { color: var(--faint); font-size: 20px; }
.comparison { display: grid; grid-template-columns: 1fr 1fr; gap: 1px; background: var(--line); border-radius: 16px; overflow: hidden; margin: 28px 0 40px; }
.comparison > div { background: var(--paper); padding: 20px; }
.comparison h4 { margin: 0 0 8px; }
.comparison p { font-family: inherit; font-size: 14px; line-height: 1.55; color: var(--muted); margin: 0; }

.checkpoint { margin: 48px 0; padding: 28px 0; border-top: 1px solid var(--line-strong); border-bottom: 1px solid var(--line-strong); }
.checkpoint .label { text-transform: uppercase; letter-spacing: .12em; color: var(--accent); font-size: 10px; font-weight: 800; }
.checkpoint h3 { font-size: 22px; line-height: 1.35; margin: 10px 0 18px; }
.checkpoint-answer { display: none; color: var(--muted); line-height: 1.65; font-size: 15px; }
.checkpoint.open .checkpoint-answer { display: block; }

.topic-connections { margin-top: 62px; }
.topic-connections h3 { font-size: 16px; margin-bottom: 14px; }
.connection-list { display: grid; gap: 1px; background: var(--line); border-radius: 15px; overflow: hidden; }
.connection { background: var(--paper); padding: 14px 16px; display: grid; grid-template-columns: 110px 1fr auto; gap: 16px; align-items: center; font-size: 13px; }
.connection-type { color: var(--accent); font-weight: 800; text-transform: uppercase; letter-spacing: .08em; font-size: 9px; }
.connection-label { color: var(--muted); }
.connection-arrow { color: var(--faint); }

.lesson-nav { display: flex; justify-content: space-between; gap: 16px; padding-top: 40px; margin-top: 48px; border-top: 1px solid var(--line); }
.lesson-nav a { max-width: 46%; color: var(--muted); font-size: 13px; }
.lesson-nav a strong { display: block; color: var(--ink); margin-top: 4px; font-size: 15px; }

.universe-head { display: flex; align-items: end; justify-content: space-between; gap: 24px; margin-bottom: 26px; }
.universe-head h1 { margin: 10px 0 0; font-size: clamp(48px, 7vw, 82px); letter-spacing: -.06em; line-height: .95; }
.universe-shell { background: #11131a; min-height: 660px; border-radius: 28px; overflow: hidden; position: relative; box-shadow: var(--shadow); }
.universe-legend { position: absolute; z-index: 5; left: 22px; top: 20px; color: rgba(255,255,255,.75); font-size: 11px; display: flex; gap: 15px; }
.universe-legend span { display: inline-flex; align-items: center; gap: 6px; }
.legend-dot { width: 8px; height: 8px; border-radius: 50%; display: inline-block; background: #9b92ff; }
.legend-dot.topic { width: 6px; height: 6px; background: #d1d5e6; }
.universe-graph { width: 100%; height: 660px; display: block; cursor: grab; }
.universe-graph:active { cursor: grabbing; }
.graph-label { fill: rgba(255,255,255,.83); font-size: 11px; pointer-events: none; }
.graph-label.course { font-weight: 800; font-size: 13px; }
.graph-link { stroke: rgba(255,255,255,.15); }
.graph-node { cursor: pointer; transition: opacity .12s; }
.graph-node:hover { opacity: .82; }

.studio-layout { display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(320px, .75fr); min-height: calc(100vh - 69px); }
.studio-editor { padding: 32px max(28px, calc((100vw - var(--content)) / 2)); padding-right: 28px; border-right: 1px solid var(--line); }
.studio-side { padding: 32px 28px; position: sticky; top: 68px; height: calc(100vh - 68px); overflow: auto; background: var(--paper); }
.studio-toolbar { display: flex; align-items: center; justify-content: space-between; gap: 14px; margin-bottom: 16px; }
.studio-toolbar h1 { margin: 0; font-size: 24px; letter-spacing: -.035em; }
.toolbar-actions { display: flex; gap: 8px; flex-wrap: wrap; }
.json-editor { width: 100%; min-height: calc(100vh - 180px); resize: vertical; border: 0; outline: none; background: transparent; color: #262833; font: 13px/1.65 "SFMono-Regular", Consolas, "Liberation Mono", monospace; tab-size: 2; }
.validation { display: flex; align-items: center; gap: 8px; font-size: 13px; font-weight: 750; margin-bottom: 22px; }
.validation.ok { color: #187862; }
.validation.error { color: var(--danger); }
.preview-title { font-size: 32px; letter-spacing: -.045em; margin: 14px 0 8px; }
.preview-description { color: var(--muted); line-height: 1.55; }
.schema-list { margin: 26px 0 0; display: grid; gap: 16px; }
.schema-item { padding-top: 14px; border-top: 1px solid var(--line); }
.schema-item strong { display: block; font-size: 13px; margin-bottom: 5px; }
.schema-item span { display: block; font-size: 12px; color: var(--muted); line-height: 1.5; }

.discussion { margin-top: 70px; padding-top: 34px; border-top: 1px solid var(--line); }
.discussion-head { display: flex; justify-content: space-between; align-items: center; gap: 16px; }
.discussion h3 { margin: 0; font-size: 23px; letter-spacing: -.03em; }
.stars-input { display: flex; gap: 4px; }
.star-button { border: 0; background: transparent; padding: 3px; cursor: pointer; font-size: 22px; color: #c9ccd5; }
.star-button.on { color: #d69a13; }
.comment-form { display: grid; grid-template-columns: 1fr auto; gap: 8px; margin: 22px 0 26px; }
.comment-form input { min-width: 0; height: 44px; border: 1px solid var(--line-strong); border-radius: 11px; padding: 0 13px; outline: none; background: var(--paper); }
.comment-form input:focus { border-color: #b8b3f8; box-shadow: 0 0 0 4px var(--accent-soft); }
.comments { display: grid; gap: 18px; }
.comment { display: grid; grid-template-columns: 34px 1fr; gap: 12px; }
.comment .avatar { width: 34px; height: 34px; }
.comment-author { display: flex; gap: 8px; align-items: baseline; font-size: 13px; font-weight: 750; }
.comment-time { color: var(--faint); font-size: 10px; font-weight: 500; }
.comment-body { margin-top: 4px; color: var(--muted); line-height: 1.52; font-size: 14px; }
.demo-note { margin-top: 18px; color: var(--faint); font-size: 12px; line-height: 1.5; }

.modal-backdrop { position: fixed; inset: 0; z-index: 80; background: rgba(16,17,22,.34); display: grid; place-items: center; padding: 24px; backdrop-filter: blur(8px); }
.modal { width: min(460px, 100%); background: var(--paper); border-radius: 22px; padding: 25px; box-shadow: 0 24px 100px rgba(0,0,0,.18); }
.modal h2 { margin: 0 0 8px; font-size: 26px; letter-spacing: -.04em; }
.modal p { color: var(--muted); line-height: 1.55; }
.modal-actions { display: flex; justify-content: flex-end; gap: 8px; margin-top: 22px; }

.toast-region { position: fixed; z-index: 120; right: 18px; bottom: 18px; display: grid; gap: 9px; }
.toast { background: #171820; color: white; border-radius: 12px; padding: 11px 14px; font-size: 13px; box-shadow: 0 14px 40px rgba(0,0,0,.18); animation: toast-in .2s ease; }
@keyframes toast-in { from { transform: translateY(8px); opacity: 0; } }

.site-footer { width: min(var(--content), calc(100% - 48px)); margin: 0 auto; min-height: 64px; border-top: 1px solid var(--line); display: flex; justify-content: space-between; align-items: center; color: var(--faint); font-size: 11px; }

.skeleton { position: relative; overflow: hidden; background: #eceef3; border-radius: 12px; }
.skeleton::after { content: ""; position: absolute; inset: 0; transform: translateX(-100%); background: linear-gradient(90deg, transparent, rgba(255,255,255,.62), transparent); animation: shimmer 1.4s infinite; }
@keyframes shimmer { to { transform: translateX(100%); } }

@media (max-width: 960px) {
  .topbar { grid-template-columns: auto 1fr auto; padding-inline: 18px; }
  .topnav { justify-content: center; }
  .course-card { grid-column: span 12; }
  .course-hero { grid-template-columns: 1fr; gap: 26px; }
  .course-statline { max-width: 480px; }
  .course-layout { grid-template-columns: 1fr; gap: 28px; }
  .topic-rail { position: static; max-height: none; display: flex; gap: 8px; overflow-x: auto; padding-bottom: 10px; }
  .module-group { min-width: 250px; }
  .module-group + .module-group { margin-top: 0; }
  .reader { max-width: none; }
  .studio-layout { grid-template-columns: 1fr; }
  .studio-editor { border-right: 0; padding: 26px 24px; }
  .studio-side { position: static; height: auto; border-top: 1px solid var(--line); }
}

@media (max-width: 720px) {
  .topbar {
    height: 58px;
    grid-template-columns: 30px minmax(0, 1fr) 38px;
    gap: 8px;
    padding-inline: 12px;
  }

  .brand {
    width: 30px;
    min-width: 30px;
    gap: 0;
    overflow: hidden;
  }

  .brand > span:last-child {
    display: none;
  }

  .brand-mark {
    width: 24px;
    min-width: 24px;
  }

  .topnav {
    position: static;
    z-index: auto;
    left: auto;
    bottom: auto;
    transform: none;
    min-width: 0;
    width: 100%;
    justify-content: center;
    gap: 2px;
    padding: 0;
    border: 0;
    border-radius: 0;
    background: transparent;
    box-shadow: none;
    backdrop-filter: none;
  }

  .topnav a {
    flex: 0 1 auto;
    min-width: 0;
    padding: 7px clamp(5px, 1.5vw, 8px);
    border-radius: 999px;
    font-size: clamp(9px, 2.7vw, 11px);
    line-height: 1;
    white-space: nowrap;
  }

  .account-slot {
    width: 38px;
    justify-self: end;
  }

  .account-button {
    width: 38px;
    height: 38px;
    justify-content: center;
    padding: 5px;
  }

  .account-button .account-name { display: none; }
  .page { width: min(100% - 30px, var(--content)); padding-top: 34px; }
  .display { font-size: clamp(42px, 15vw, 67px); }
  .hero { padding-top: 28px; }
  .micro-features { grid-template-columns: 1fr; gap: 20px; }
  .course-card { min-height: 330px; padding: 22px; }
  .course-footer { left: 22px; right: 22px; bottom: 20px; align-items: flex-end; }
  .course-hero h1 { font-size: clamp(42px, 13vw, 64px); }
  .course-statline { grid-template-columns: repeat(2, 1fr); }
  .lesson-section p, .lesson-section li { font-size: 17px; }
  .comparison { grid-template-columns: 1fr; }
  .connection { grid-template-columns: 88px 1fr; }
  .connection-arrow { display: none; }
  .universe-shell, .universe-graph { height: 560px; min-height: 560px; }
  .universe-head { align-items: start; flex-direction: column; }
  .studio-toolbar { align-items: start; flex-direction: column; }
  .comment-form { grid-template-columns: 1fr; }
  .site-footer { padding-bottom: 76px; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; animation-duration: .001ms !important; animation-iteration-count: 1 !important; transition-duration: .001ms !important; }
}


/* Full-screen Universe — canvas-first knowledge graph */
body.universe-mode {
  overflow: hidden;
  background: #0b0d12;
}
body.universe-mode .topbar {
  background: rgba(11, 13, 18, .88);
  color: rgba(255,255,255,.94);
  border-bottom-color: rgba(255,255,255,.08);
  backdrop-filter: blur(18px) saturate(135%);
}
body.universe-mode .topnav a {
  color: rgba(255,255,255,.58);
}
body.universe-mode .topnav a:hover,
body.universe-mode .topnav a.active {
  color: white;
  background: rgba(255,255,255,.08);
  box-shadow: none;
}
body.universe-mode .account-button {
  color: rgba(255,255,255,.9);
  background: rgba(255,255,255,.06);
  border-color: rgba(255,255,255,.1);
}
body.universe-mode .site-footer {
  display: none;
}
body.universe-mode #app {
  min-height: 0;
  height: calc(100dvh - 68px);
}

.universe-full {
  position: relative;
  width: 100%;
  height: 100%;
  overflow: hidden;
  background:
    radial-gradient(circle at 50% 50%, rgba(92,84,210,.08), transparent 38%),
    #0b0d12;
}
.universe-canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  cursor: grab;
}
.universe-canvas:active {
  cursor: grabbing;
}
.universe-canvas canvas {
  display: block;
}

.universe-titlebar {
  position: absolute;
  z-index: 8;
  top: 28px;
  left: 32px;
  width: min(350px, calc(100vw - 64px));
  pointer-events: none;
  color: white;
}
.universe-overline {
  display: block;
  margin-bottom: 10px;
  color: #9b92ff;
  font-size: 10px;
  font-weight: 800;
  letter-spacing: .14em;
  text-transform: uppercase;
}
.universe-titlebar h1 {
  margin: 0;
  max-width: 320px;
  font-size: clamp(27px, 3vw, 42px);
  line-height: .98;
  letter-spacing: -.055em;
}
.universe-titlebar p {
  margin: 12px 0 0;
  max-width: 310px;
  color: rgba(238,240,248,.55);
  font-size: 12px;
  line-height: 1.55;
}
.universe-stats {
  display: block;
  margin-top: 10px;
  color: rgba(238,240,248,.34);
  font-size: 10px;
  letter-spacing: .015em;
}

.universe-search-wrap {
  position: absolute;
  z-index: 12;
  top: 28px;
  left: 50%;
  width: min(430px, calc(100vw - 760px));
  min-width: 300px;
  transform: translateX(-50%);
}
.universe-searchbox {
  height: 44px;
  display: grid;
  grid-template-columns: 20px 1fr auto;
  align-items: center;
  gap: 8px;
  padding: 0 11px 0 13px;
  border: 1px solid rgba(255,255,255,.105);
  border-radius: 14px;
  background: rgba(20,22,29,.78);
  box-shadow: 0 14px 40px rgba(0,0,0,.18);
  backdrop-filter: blur(18px) saturate(135%);
  color: rgba(255,255,255,.48);
}
.universe-searchbox:focus-within {
  border-color: rgba(151,140,255,.5);
  background: rgba(23,25,34,.94);
  box-shadow: 0 0 0 3px rgba(126,114,255,.11), 0 18px 48px rgba(0,0,0,.24);
}
.universe-searchbox input {
  min-width: 0;
  border: 0;
  outline: 0;
  background: transparent;
  color: white;
  font-size: 13px;
}
.universe-searchbox input::placeholder {
  color: rgba(255,255,255,.34);
}
.universe-searchbox kbd {
  border: 1px solid rgba(255,255,255,.09);
  border-radius: 6px;
  padding: 3px 6px;
  background: rgba(255,255,255,.04);
  color: rgba(255,255,255,.33);
  font-size: 9px;
  font-family: inherit;
}
.universe-search-results {
  margin-top: 8px;
  padding: 6px;
  border: 1px solid rgba(255,255,255,.08);
  border-radius: 14px;
  background: rgba(17,19,26,.96);
  box-shadow: 0 20px 70px rgba(0,0,0,.34);
  backdrop-filter: blur(18px);
}
.universe-search-results button {
  width: 100%;
  display: grid;
  grid-template-columns: 68px minmax(0,1fr);
  gap: 10px;
  align-items: center;
  padding: 9px 10px;
  border: 0;
  border-radius: 9px;
  background: transparent;
  color: white;
  text-align: left;
  cursor: pointer;
}
.universe-search-results button:hover {
  background: rgba(255,255,255,.065);
}
.universe-search-results button span {
  color: rgba(155,146,255,.82);
  font-size: 9px;
  font-weight: 800;
  letter-spacing: .08em;
  text-transform: uppercase;
}
.universe-search-results button strong {
  overflow: hidden;
  font-size: 12px;
  font-weight: 620;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.universe-search-empty {
  padding: 12px;
  color: rgba(255,255,255,.4);
  font-size: 11px;
}

.universe-actions {
  position: absolute;
  z-index: 10;
  top: 28px;
  right: 28px;
  display: flex;
  gap: 7px;
}
.universe-control {
  width: 42px;
  height: 42px;
  display: grid;
  place-items: center;
  border: 1px solid rgba(255,255,255,.095);
  border-radius: 12px;
  background: rgba(19,21,28,.76);
  color: rgba(255,255,255,.62);
  cursor: pointer;
  backdrop-filter: blur(15px);
  transition: .16s ease;
}
.universe-control:hover,
.universe-control.active {
  color: white;
  border-color: rgba(157,147,255,.38);
  background: rgba(113,101,236,.17);
  transform: translateY(-1px);
}
.universe-control span {
  font-size: 12px;
  font-weight: 750;
}

.universe-legend {
  position: absolute;
  z-index: 8;
  left: 32px;
  bottom: 18px;
  display: flex;
  align-items: center;
  gap: 14px;
  color: rgba(255,255,255,.58);
  font-size: 10px;
  pointer-events: none;
}
.universe-legend-bottom {
  width: fit-content;
  max-width: calc(100vw - 64px);
  padding: 10px 13px;
  border: 1px solid rgba(255,255,255,.06);
  border-radius: 12px;
  background: rgba(15,18,26,.72);
  box-shadow: 0 10px 34px rgba(0,0,0,.18);
  backdrop-filter: blur(14px);
}
.universe-legend span {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}
.universe-legend-hint {
  margin-left: 8px;
  padding-left: 16px;
  border-left: 1px solid rgba(255,255,255,.11);
  color: rgba(255,255,255,.26);
}
.universe-legend .legend-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #8d82ff;
  box-shadow: 0 0 16px rgba(141,130,255,.35);
}
.universe-legend .legend-dot.topic {
  width: 6px;
  height: 6px;
  background: #d6dae7;
  box-shadow: none;
}

.universe-inspector {
  position: absolute;
  z-index: 11;
  right: 28px;
  bottom: 28px;
  width: min(340px, calc(100vw - 56px));
  padding: 19px 19px 17px;
  border: 1px solid rgba(255,255,255,.09);
  border-radius: 17px;
  background: rgba(17,19,26,.88);
  color: white;
  box-shadow: 0 24px 80px rgba(0,0,0,.32);
  backdrop-filter: blur(20px) saturate(135%);
}
.universe-inspector[hidden] {
  display: none;
}
.universe-inspector-type {
  color: #9b92ff;
  font-size: 9px;
  font-weight: 800;
  letter-spacing: .12em;
  text-transform: uppercase;
}
.universe-inspector h2 {
  margin: 8px 28px 8px 0;
  font-size: 22px;
  line-height: 1.08;
  letter-spacing: -.035em;
}
.universe-inspector p {
  margin: 0;
  color: rgba(235,237,245,.55);
  font-size: 12px;
  line-height: 1.55;
}
.universe-inspector-meta {
  margin-top: 13px;
  color: rgba(255,255,255,.31);
  font-size: 10px;
}
.universe-inspector-close {
  position: absolute;
  top: 10px;
  right: 11px;
  width: 28px;
  height: 28px;
  border: 0;
  border-radius: 8px;
  background: transparent;
  color: rgba(255,255,255,.42);
  font-size: 18px;
  cursor: pointer;
}
.universe-inspector-close:hover {
  color: white;
  background: rgba(255,255,255,.06);
}
.universe-open-button {
  margin-top: 16px;
  height: 38px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 12px;
  border-radius: 10px;
  background: rgba(141,130,255,.14);
  color: #d8d4ff;
  font-size: 12px;
  font-weight: 700;
  transition: .16s ease;
}
.universe-open-button:hover {
  background: rgba(141,130,255,.22);
  color: white;
}
.force-graph-container .graph-tooltip {
  padding: 7px 9px !important;
  border: 1px solid rgba(255,255,255,.08) !important;
  border-radius: 8px !important;
  background: rgba(13,15,21,.92) !important;
  color: rgba(255,255,255,.84) !important;
  box-shadow: 0 10px 30px rgba(0,0,0,.28) !important;
  font: 11px/1.35 Inter, ui-sans-serif, system-ui, sans-serif !important;
}

@media (max-width: 1050px) {
  .universe-search-wrap {
    top: auto;
    left: 32px;
    bottom: 62px;
    width: min(430px, calc(100vw - 64px));
    min-width: 0;
    transform: none;
  }
  .universe-legend {
    left: 18px;
    right: 18px;
    max-width: none;
    overflow-x: auto;
    scrollbar-width: none;
  }
  .universe-legend::-webkit-scrollbar {
    display: none;
  }
}

@media (max-width: 720px) {
  body.universe-mode #app {
    height: calc(100dvh - 58px);
  }
  body.universe-mode .topnav {
    background: transparent;
    border: 0;
  }
  .universe-titlebar {
    top: 20px;
    left: 18px;
    width: calc(100vw - 88px);
  }
  .universe-titlebar h1 {
    max-width: 260px;
    font-size: 28px;
  }
  .universe-titlebar p {
    display: none;
  }
  .universe-actions {
    top: 18px;
    right: 16px;
    flex-direction: column;
    align-items: flex-end;
  }
  .universe-control {
    width: 38px;
    height: 38px;
  }
  .universe-legend-bottom {
    left: 14px;
    right: 14px;
    bottom: 14px;
    max-width: none;
  }
  .universe-legend-hint {
    display: none;
  }
  .universe-search-wrap {
    left: 16px;
    bottom: 78px;
    width: calc(100vw - 32px);
  }
  .universe-inspector {
    right: 16px;
    bottom: 136px;
    width: calc(100vw - 32px);
  }
}


/* Catalog -> Library -> Lesson hierarchy */
.collection-hero {
  display: flex;
  align-items: end;
  justify-content: space-between;
  gap: 42px;
  padding: 26px 0 44px;
  border-bottom: 1px solid var(--line);
}
.collection-hero.compact {
  padding-top: 18px;
}
.collection-hero h1 {
  margin: 12px 0 14px;
  max-width: 820px;
  font-size: clamp(46px, 7vw, 78px);
  line-height: .98;
  letter-spacing: -.06em;
}
.collection-actions {
  display: flex;
  gap: 9px;
  flex-wrap: wrap;
  justify-content: flex-end;
  padding-bottom: 4px;
}
.catalog-stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  margin: 28px 0 48px;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--line);
}
.catalog-stats > div {
  min-height: 92px;
  padding: 18px;
  background: var(--paper);
}
.catalog-stats strong {
  display: block;
  font-size: 24px;
  letter-spacing: -.035em;
}
.catalog-stats span {
  display: block;
  margin-top: 5px;
  color: var(--muted);
  font-size: 11px;
}
.catalog-notice {
  margin: 8px 0 36px;
  padding: 16px 18px;
  border-left: 3px solid var(--accent);
  background: color-mix(in srgb, var(--accent-soft) 58%, white);
}
.catalog-notice strong {
  display: block;
  margin-bottom: 4px;
  font-size: 13px;
}
.catalog-notice p {
  margin: 0;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.55;
}
.catalog-card::before {
  content: "CATALOGO";
  position: absolute;
  top: 23px;
  right: 24px;
  z-index: 2;
  color: color-mix(in srgb, var(--card-accent) 75%, #111);
  font-size: 9px;
  font-weight: 850;
  letter-spacing: .13em;
}
.collection-list {
  margin-top: 24px;
}
.library-row {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 30px;
  padding: 26px 2px;
  border-top: 1px solid var(--line);
  transition: transform .18s ease, border-color .18s ease;
}
.library-row:last-child {
  border-bottom: 1px solid var(--line);
}
.library-row:hover {
  transform: translateX(5px);
  border-color: var(--line-strong);
}
.library-row h3 {
  margin: 8px 0 8px;
  font-size: clamp(26px, 3vw, 38px);
  letter-spacing: -.045em;
}
.library-row p {
  max-width: 720px;
  margin: 0;
  color: var(--muted);
  line-height: 1.55;
}
.library-row-meta {
  display: grid;
  grid-template-columns: auto auto;
  gap: 2px 8px;
  align-items: baseline;
  min-width: 180px;
}
.library-row-meta strong {
  font-size: 18px;
}
.library-row-meta span {
  color: var(--muted);
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: .08em;
}
.library-row-meta .library-row-arrow {
  grid-column: 1 / -1;
  margin-top: 8px;
  color: var(--ink);
  font-size: 20px;
  text-align: right;
}
.lesson-list {
  margin-top: 44px;
}
.lesson-row {
  border-top: 1px solid var(--line);
}
.lesson-row:last-child {
  border-bottom: 1px solid var(--line);
}
.lesson-row-main {
  display: grid;
  grid-template-columns: 52px minmax(0, 1fr) auto;
  gap: 20px;
  align-items: center;
  padding: 23px 0 11px;
}
.lesson-row-main:hover h3 {
  color: var(--accent);
}
.lesson-index {
  align-self: start;
  padding-top: 4px;
  color: var(--faint);
  font-size: 12px;
  font-variant-numeric: tabular-nums;
}
.lesson-row h3 {
  margin: 0 0 7px;
  font-size: 22px;
  letter-spacing: -.03em;
  transition: color .15s ease;
}
.lesson-row p {
  max-width: 720px;
  margin: 0;
  color: var(--muted);
  font-size: 13px;
  line-height: 1.55;
}
.lesson-meta {
  display: grid;
  grid-template-columns: auto auto;
  gap: 1px 7px;
  align-items: baseline;
  min-width: 122px;
}
.lesson-meta strong {
  font-size: 15px;
}
.lesson-meta span {
  color: var(--faint);
  font-size: 9px;
  text-transform: uppercase;
  letter-spacing: .08em;
}
.lesson-universe-link {
  display: inline-block;
  margin: 0 0 18px 72px;
  color: var(--accent);
  font-size: 11px;
  font-weight: 700;
}
.breadcrumb {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 18px;
  color: var(--muted);
  font-size: 11px;
}
.breadcrumb a:hover {
  color: var(--ink);
}
.breadcrumb strong {
  color: var(--ink);
}
.lesson-hero .breadcrumb {
  margin-bottom: 14px;
}

/* Universe type legend */
.universe-legend .legend-dot.catalog {
  width: 10px;
  height: 10px;
  background: #8d82ff;
}
.universe-legend .legend-dot.library {
  width: 9px;
  height: 9px;
  background: #4db8ff;
}
.universe-legend .legend-dot.lesson {
  width: 8px;
  height: 8px;
  background: #ffb36b;
}
.universe-legend .legend-dot.topic {
  width: 6px;
  height: 6px;
  background: #d7dbea;
}

@media (max-width: 850px) {
  .collection-hero {
    align-items: start;
    flex-direction: column;
    gap: 20px;
  }
  .collection-actions {
    justify-content: flex-start;
  }
  .catalog-stats {
    grid-template-columns: repeat(2, 1fr);
  }
  .library-row {
    grid-template-columns: 1fr;
    gap: 16px;
  }
  .library-row-meta {
    min-width: 0;
    max-width: 200px;
  }
  .lesson-row-main {
    grid-template-columns: 36px minmax(0, 1fr);
  }
  .lesson-meta {
    grid-column: 2;
    min-width: 0;
    max-width: 150px;
  }
  .lesson-universe-link {
    margin-left: 56px;
  }
}

@media (max-width: 560px) {
  .catalog-stats {
    grid-template-columns: 1fr 1fr;
  }
  .collection-hero h1 {
    font-size: 48px;
  }
  .lesson-row-main {
    gap: 12px;
  }
}


/* Universe legend: plain color key, no container */
body.universe-mode .universe-legend {
  position: absolute;
  z-index: 12;
  left: 30px;
  right: auto;
  bottom: 24px;
  top: auto;
  width: auto;
  max-width: calc(100vw - 60px);
  height: auto;
  min-height: 0;
  padding: 0;
  margin: 0;
  border: 0;
  border-radius: 0;
  background: transparent;
  box-shadow: none;
  backdrop-filter: none;
  -webkit-backdrop-filter: none;
  display: flex;
  align-items: center;
  gap: 16px;
  overflow: visible;
  color: rgba(255,255,255,.62);
  pointer-events: none;
}

body.universe-mode .universe-legend span {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  flex: 0 0 auto;
}

body.universe-mode .universe-legend-hint {
  display: none;
}

@media (max-width: 720px) {
  body.universe-mode .universe-legend {
    left: 16px;
    right: 16px;
    bottom: 14px;
    width: auto;
    max-width: none;
    gap: 10px 12px;
    overflow-x: auto;
    scrollbar-width: none;
  }

  body.universe-mode .universe-legend::-webkit-scrollbar {
    display: none;
  }
}