/* ============ Design tokens ============ */
:root {
  --font: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', sans-serif;
  --mono: 'SF Mono', SFMono-Regular, ui-monospace, Menlo, Consolas, monospace;
  --radius: 8px; --radius-lg: 14px;
  --topbar-h: 56px; --sidebar-w: 288px; --toc-w: 220px;
  --shadow: 0 4px 24px rgba(0,0,0,.12);
  --ease: 180ms cubic-bezier(.2,.7,.3,1);
}
html[data-theme="light"] {
  --bg: #faf9f6; --bg-raise: #ffffff; --bg-sunk: #f1efe8;
  --ink: #2b2836; --ink-soft: #5d5a6b; --ink-faint: #8d8a9b;
  --accent: #4f46e5; --accent-2: #9333ea; --accent-soft: #eef0ff; --accent-ink: #ffffff;
  --border: #e6e3d9; --code-bg: #f2f0e9; --mark: #fff3bf;
  --ok: #16803c; --ok-soft: #e5f5ea;
}
html[data-theme="dark"] {
  --bg: #0f172a; --bg-raise: #16203a; --bg-sunk: #0b1220;
  --ink: #d7deeb; --ink-soft: #97a3b8; --ink-faint: #64748b;
  --accent: #818cf8; --accent-2: #c084fc; --accent-soft: #232b52; --accent-ink: #0b1220;
  --border: #22304f; --code-bg: #1a2440; --mark: #57500f;
  --ok: #4ade80; --ok-soft: #12331f;
  color-scheme: dark;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation: none !important; transition: none !important; }
}
body {
  margin: 0; font-family: var(--font); font-size: 16px; line-height: 1.65;
  background: var(--bg); color: var(--ink);
}
.skip-link {
  position: absolute; left: -9999px; top: 8px; z-index: 200;
  background: var(--accent); color: var(--accent-ink); padding: 8px 16px; border-radius: var(--radius);
}
.skip-link:focus { left: 8px; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 3px; }

/* ============ Top bar ============ */
.topbar {
  position: fixed; inset: 0 0 auto 0; height: var(--topbar-h); z-index: 60;
  display: flex; align-items: center; gap: 10px; padding: 0 14px;
  background: color-mix(in srgb, var(--bg-raise) 88%, transparent);
  backdrop-filter: blur(10px); border-bottom: 1px solid var(--border);
}
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--ink); }
.brand-mark {
  font-family: var(--mono); font-weight: 700; color: var(--accent-ink);
  background: var(--accent); border-radius: 8px; padding: 4px 7px; font-size: 13px;
}
.brand-text { font-weight: 650; font-size: 15px; line-height: 1.15; display: flex; flex-direction: column; }
.brand-text small { font-weight: 400; color: var(--ink-faint); font-size: 11px; }
.search-trigger {
  margin-left: auto; display: flex; align-items: center; gap: 8px;
  font: inherit; font-size: 13.5px; color: var(--ink-soft); cursor: pointer;
  background: var(--bg-sunk); border: 1px solid var(--border); border-radius: 999px;
  padding: 6px 12px; min-width: 200px; transition: border-color var(--ease);
}
.search-trigger:hover { border-color: var(--accent); }
.search-trigger kbd { margin-left: auto; }
kbd {
  font-family: var(--mono); font-size: 11px; color: var(--ink-soft);
  background: var(--bg-raise); border: 1px solid var(--border); border-bottom-width: 2px;
  border-radius: 5px; padding: 1px 5px;
}
.top-actions { display: flex; align-items: center; gap: 6px; }
.icon-btn {
  font: inherit; font-size: 13.5px; color: var(--ink-soft); cursor: pointer; text-decoration: none;
  background: none; border: 1px solid transparent; border-radius: var(--radius);
  padding: 6px 10px; transition: background var(--ease);
}
.icon-btn:hover { background: var(--bg-sunk); color: var(--ink); }
.progress-mini { width: 24px; height: 24px; display: flex; align-items: center; justify-content: center; }
.progress-mini svg { display: block; width: 24px; height: 24px; }
.ring-fg { transition: stroke-dashoffset .7s cubic-bezier(.3,.7,.3,1); }
#nav-toggle { display: none; }
.burger, .burger::before, .burger::after {
  content: ''; display: block; width: 16px; height: 2px; background: var(--ink-soft); border-radius: 2px;
}
.burger { position: relative; }
.burger::before { position: absolute; top: -5px; } .burger::after { position: absolute; top: 5px; }

/* ============ Layout ============ */
.layout { display: grid; grid-template-columns: var(--sidebar-w) minmax(0,1fr) var(--toc-w); }
.sidebar {
  position: sticky; top: var(--topbar-h); height: calc(100vh - var(--topbar-h));
  overflow-y: auto; padding: 14px 10px 40px; border-right: 1px solid var(--border);
  background: var(--bg); scrollbar-width: thin;
}
.sidebar-filter { padding: 0 6px 10px; }
#nav-filter {
  width: 100%; font: inherit; font-size: 13px; color: var(--ink);
  background: var(--bg-sunk); border: 1px solid var(--border); border-radius: var(--radius); padding: 6px 10px;
}
.nav-group > h3 {
  font-size: 11px; letter-spacing: .08em; text-transform: uppercase; color: var(--ink-faint);
  margin: 18px 8px 6px; font-weight: 650;
}
.nav-item {
  display: flex; align-items: center; gap: 8px; text-decoration: none;
  color: var(--ink-soft); font-size: 13.5px; padding: 5px 8px; border-radius: var(--radius);
  border-left: 2px solid transparent; transition: background var(--ease);
}
.nav-item:hover { background: var(--bg-sunk); color: var(--ink); }
.nav-item.is-active { color: var(--accent); background: var(--accent-soft); border-left-color: var(--accent); font-weight: 600; }
.nav-item .dot {
  flex: none; width: 8px; height: 8px; border-radius: 50%;
  border: 1.5px solid var(--ink-faint); background: transparent;
}
.nav-item.is-done .dot { background: var(--ok); border-color: var(--ok); }
.nav-item.in-progress .dot { border-color: var(--accent); background: var(--accent-soft); }
.nav-item .mins { margin-left: auto; font-size: 11px; color: var(--ink-faint); }
.sidebar-scrim { position: fixed; inset: 0; z-index: 49; background: rgba(0,0,0,.45); }

.content { padding: calc(var(--topbar-h) + 26px) 48px 80px; max-width: 900px; margin: 0 auto; width: 100%; }
.toc {
  position: sticky; top: var(--topbar-h); height: calc(100vh - var(--topbar-h));
  overflow-y: auto; padding: 26px 16px 40px; font-size: 12.5px; scrollbar-width: thin;
}
.toc h4 { font-size: 11px; text-transform: uppercase; letter-spacing: .08em; color: var(--ink-faint); margin: 0 0 8px; }
.toc a {
  display: block; color: var(--ink-soft); text-decoration: none; padding: 3px 8px;
  border-left: 2px solid var(--border); line-height: 1.4;
}
.toc a.lvl-3 { padding-left: 20px; }
.toc a:hover { color: var(--ink); }
.toc a.is-current { color: var(--accent); border-left-color: var(--accent); font-weight: 600; }

/* ============ Article ============ */
.crumbs { font-size: 12.5px; color: var(--ink-faint); margin-bottom: 6px; }
.crumbs a { color: var(--ink-faint); text-decoration: none; } .crumbs a:hover { color: var(--accent); }
.page-tools {
  display: flex; flex-wrap: wrap; align-items: center; gap: 8px; margin: 10px 0 26px;
  padding-bottom: 14px; border-bottom: 1px solid var(--border); font-size: 12.5px; color: var(--ink-faint);
}
.page-tools .spacer { flex: 1; }
.tool-btn {
  font: inherit; font-size: 12.5px; cursor: pointer; color: var(--ink-soft);
  background: var(--bg-sunk); border: 1px solid var(--border); border-radius: 999px; padding: 4px 12px;
  transition: border-color var(--ease);
}
.tool-btn:hover { border-color: var(--accent); color: var(--ink); }
.tool-btn.is-on { background: var(--accent-soft); color: var(--accent); border-color: var(--accent); }
.tool-btn.done-on { background: var(--ok-soft); color: var(--ok); border-color: var(--ok); }

.md h1 { font-size: 30px; line-height: 1.25; margin: 0 0 4px; letter-spacing: -.015em; }
.md h2 { font-size: 21px; margin: 40px 0 12px; padding-top: 8px; letter-spacing: -.01em; scroll-margin-top: 76px; }
.md h3 { font-size: 16.5px; margin: 26px 0 8px; scroll-margin-top: 76px; }
.md h4 { font-size: 14.5px; scroll-margin-top: 76px; }
.md p, .md li { color: var(--ink); }
.md a { color: var(--accent); text-decoration: none; border-bottom: 1px solid transparent; }
.md a:hover { border-bottom-color: var(--accent); }
.md blockquote {
  margin: 14px 0; padding: 10px 16px; border-left: 3px solid var(--accent);
  background: var(--accent-soft); border-radius: 0 var(--radius) var(--radius) 0; color: var(--ink);
}
.md blockquote p { margin: 6px 0; }
.md table { border-collapse: collapse; width: 100%; display: block; overflow-x: auto; font-size: 14px; margin: 16px 0; }
.md th, .md td { border: 1px solid var(--border); padding: 7px 11px; text-align: left; vertical-align: top; }
.md th { background: var(--bg-sunk); font-weight: 650; }
.md tr:nth-child(even) td { background: color-mix(in srgb, var(--bg-sunk) 45%, transparent); }
.md code { font-family: var(--mono); font-size: .86em; background: var(--code-bg); border-radius: 5px; padding: 2px 5px; }
.md pre {
  background: var(--code-bg); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px 16px; overflow-x: auto; font-size: 13px; line-height: 1.55; position: relative;
}
.md pre code { background: none; padding: 0; font-size: inherit; }
.md hr { border: none; border-top: 1px solid var(--border); margin: 32px 0; }
.md img, .md svg { max-width: 100%; }
mark { background: var(--mark); border-radius: 3px; padding: 0 2px; }

/* Heading anchors */
.h-anchor { opacity: 0; margin-left: 6px; font-size: .8em; text-decoration: none; color: var(--ink-faint); }
h2:hover .h-anchor, h3:hover .h-anchor { opacity: 1; }

/* Code block chrome: header w/ language + copy */
.codeblock { position: relative; margin: 14px 0; }
.codeblock .code-head {
  display: flex; align-items: center; justify-content: space-between;
  font-family: var(--mono); font-size: 11px; color: var(--ink-faint);
  background: var(--bg-sunk); border: 1px solid var(--border); border-bottom: none;
  border-radius: var(--radius) var(--radius) 0 0; padding: 4px 12px;
}
.codeblock pre { margin: 0; border-radius: 0 0 var(--radius) var(--radius); }
.copy-btn { font: inherit; cursor: pointer; background: none; border: none; color: var(--ink-faint); padding: 2px 6px; border-radius: 4px; }
.copy-btn:hover { color: var(--accent); background: var(--bg-raise); }
.copy-btn.copied { color: var(--ok); }

/* JS / Python tabs */
.lang-tabs { margin: 14px 0; border: 1px solid var(--border); border-radius: var(--radius); overflow: hidden; }
.lang-tabs [role="tablist"] { display: flex; gap: 2px; background: var(--bg-sunk); padding: 4px 6px 0; }
.lang-tabs [role="tab"] {
  font: inherit; font-size: 12.5px; font-weight: 600; cursor: pointer; color: var(--ink-faint);
  background: none; border: none; padding: 6px 14px; border-radius: 6px 6px 0 0;
}
.lang-tabs [role="tab"][aria-selected="true"] { background: var(--code-bg); color: var(--accent); }
.lang-tabs [role="tabpanel"] > .codeblock { margin: 0; }
.lang-tabs [role="tabpanel"] > .codeblock pre, .lang-tabs [role="tabpanel"] .code-head { border: none; border-radius: 0; }
.lang-tabs [role="tabpanel"][hidden] { display: none; }

/* Collapsible sections */
.sec-toggle {
  font: inherit; cursor: pointer; background: none; border: none; color: var(--ink-faint);
  padding: 0 6px; font-size: 13px; vertical-align: middle;
}
.sec-collapsed-note { color: var(--ink-faint); font-size: 12.5px; font-style: italic; margin: 4px 0 0; }
[data-collapsed] { display: none !important; }

/* Mermaid */
.mermaid { text-align: center; margin: 18px 0; }
.mermaid-pending { color: var(--ink-faint); font-size: 12.5px; }

/* Pager */
.pager { display: flex; gap: 14px; max-width: 900px; margin: 44px auto 0; padding: 0; }
.pager a {
  flex: 1; text-decoration: none; border: 1px solid var(--border); border-radius: var(--radius-lg);
  padding: 12px 16px; color: var(--ink); background: var(--bg-raise); transition: border-color var(--ease);
}
.pager a:hover { border-color: var(--accent); }
.pager .dir { font-size: 11px; text-transform: uppercase; letter-spacing: .07em; color: var(--ink-faint); }
.pager .next { text-align: right; }

/* ============ Dashboard ============ */
.hero { display: flex; align-items: center; gap: 26px; margin-bottom: 30px; flex-wrap: wrap; }
.hero h1 { margin: 0 0 6px; font-size: 30px; }
.hero p { margin: 0; color: var(--ink-soft); max-width: 52ch; }
.hero .ring { flex: none; filter: drop-shadow(0 3px 10px color-mix(in srgb, var(--accent) 22%, transparent)); }
.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 14px; margin: 22px 0; }
.card {
  background: var(--bg-raise); border: 1px solid var(--border); border-radius: var(--radius-lg);
  padding: 16px 18px; text-decoration: none; color: var(--ink); display: block;
  transition: transform var(--ease), border-color var(--ease);
}
a.card:hover { transform: translateY(-2px); border-color: var(--accent); }
.card h3 { margin: 0 0 4px; font-size: 15px; }
.card p { margin: 0; font-size: 13px; color: var(--ink-soft); }
.card .bignum { font-size: 26px; font-weight: 700; color: var(--accent); }
.path-row { display: flex; align-items: center; gap: 12px; padding: 9px 4px; border-bottom: 1px solid var(--border); }
.path-row:last-child { border-bottom: none; }
.path-row .name { width: 220px; flex: none; font-size: 13.5px; }
.path-row a { color: var(--ink); text-decoration: none; } .path-row a:hover { color: var(--accent); }
.bar { flex: 1; height: 7px; border-radius: 4px; background: var(--bg-sunk); overflow: hidden; }
.bar i { display: block; height: 100%; background: var(--accent); border-radius: 4px; transition: width .4s ease; }
.path-row .pct { width: 78px; text-align: right; font-size: 12px; color: var(--ink-faint); font-variant-numeric: tabular-nums; }
.section-h { font-size: 13px; text-transform: uppercase; letter-spacing: .07em; color: var(--ink-faint); margin: 34px 0 10px; }

/* ============ Practice / flashcards ============ */
.flash {
  background: var(--bg-raise); border: 1px solid var(--border); border-radius: var(--radius-lg);
  padding: 26px 28px; margin: 18px 0; box-shadow: var(--shadow);
}
.flash .q { font-size: 17px; font-weight: 650; }
.flash .a { border-top: 1px dashed var(--border); margin-top: 18px; padding-top: 18px; }
.flash-actions { display: flex; gap: 10px; margin-top: 18px; flex-wrap: wrap; }
.btn {
  font: inherit; font-size: 14px; font-weight: 600; cursor: pointer;
  border-radius: var(--radius); padding: 8px 18px; border: 1px solid var(--border);
  background: var(--bg-sunk); color: var(--ink); transition: border-color var(--ease);
}
.btn:hover { border-color: var(--accent); }
.btn.primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.btn.good { background: var(--ok-soft); color: var(--ok); border-color: var(--ok); }
.flash-meta { font-size: 12.5px; color: var(--ink-faint); margin-bottom: 10px; }

/* ============ Modals ============ */
.modal { position: fixed; inset: 0; z-index: 100; background: rgba(10,12,25,.5); display: flex; align-items: flex-start; justify-content: center; padding: 9vh 16px 16px; }
.modal[hidden] { display: none; }
.modal-box {
  width: 100%; max-width: 640px; max-height: 76vh; overflow: hidden auto;
  background: var(--bg-raise); border: 1px solid var(--border); border-radius: var(--radius-lg);
  box-shadow: var(--shadow); padding: 14px;
}
#search-input { width: 100%; font: inherit; font-size: 16px; color: var(--ink); background: var(--bg-sunk); border: 1px solid var(--border); border-radius: var(--radius); padding: 11px 14px; }
.search-filters { display: flex; gap: 6px; margin: 10px 0; }
.chip { font: inherit; font-size: 12px; cursor: pointer; border-radius: 999px; padding: 3px 12px; border: 1px solid var(--border); background: none; color: var(--ink-soft); }
.chip.is-on { background: var(--accent-soft); color: var(--accent); border-color: var(--accent); }
#search-results { list-style: none; margin: 4px 0 0; padding: 0; }
#search-results li { border-radius: var(--radius); padding: 9px 12px; cursor: pointer; }
#search-results li.is-sel, #search-results li:hover { background: var(--accent-soft); }
#search-results .r-head { font-size: 14px; font-weight: 600; }
#search-results .r-crumb { font-size: 11.5px; color: var(--ink-faint); }
#search-results .r-snip { font-size: 12.5px; color: var(--ink-soft); margin-top: 2px; }
.shortcuts { display: grid; grid-template-columns: 1fr 1fr; gap: 8px 22px; margin: 14px 0 4px; }
.shortcuts div { display: flex; justify-content: space-between; gap: 12px; font-size: 13.5px; }
.shortcuts dt { color: var(--ink-soft); } .shortcuts dd { margin: 0; }
#bookmarks-list { list-style: none; padding: 0; }
#bookmarks-list a { display: block; padding: 8px 10px; border-radius: var(--radius); color: var(--ink); text-decoration: none; }
#bookmarks-list a:hover { background: var(--accent-soft); }

#toast {
  position: fixed; bottom: 22px; left: 50%; transform: translate(-50%, 80px); z-index: 120;
  background: var(--ink); color: var(--bg); font-size: 13.5px; border-radius: 999px;
  padding: 8px 20px; opacity: 0; transition: transform .25s ease, opacity .25s ease; pointer-events: none;
}
#toast.show { transform: translate(-50%, 0); opacity: 1; }

/* ============ Responsive ============ */
@media (max-width: 1150px) { .layout { grid-template-columns: var(--sidebar-w) minmax(0,1fr); } .toc { display: none; } }
@media (max-width: 880px) {
  .layout { grid-template-columns: minmax(0,1fr); }
  #nav-toggle { display: block; }
  .sidebar {
    position: fixed; left: 0; top: var(--topbar-h); z-index: 50; width: min(84vw, 320px);
    transform: translateX(-102%); transition: transform .22s ease; box-shadow: var(--shadow);
  }
  .sidebar.open { transform: none; }
  .content { padding: calc(var(--topbar-h) + 18px) 18px 60px; }
  .search-trigger { min-width: 0; } .search-trigger span { display: none; }
  .brand-text small { display: none; }
  .shortcuts { grid-template-columns: 1fr; }
}
@media print { .topbar, .sidebar, .toc, .pager, .page-tools { display: none !important; } .content { padding: 0; } }

/* ============ Multi-course additions ============ */
.badge {
  display: inline-block; font-size: 10.5px; font-weight: 650; letter-spacing: .04em;
  text-transform: uppercase; color: var(--accent); background: var(--accent-soft);
  border: 1px solid var(--accent); border-radius: 999px; padding: 1px 8px; vertical-align: middle;
}
.course-grid { grid-template-columns: repeat(auto-fill, minmax(270px, 1fr)); }
.course-card-top { display: flex; align-items: center; gap: 12px; margin-bottom: 6px; }
.course-card-top .ring { flex: none; }
.course-card-top h3 { margin: 0; }
.course-meta { font-size: 12px !important; color: var(--ink-faint) !important; margin-top: 8px !important; }
.nav-back { color: var(--ink-faint); font-size: 12.5px; margin-bottom: 2px; }
.nav-course { font-size: 14.5px; margin-bottom: 4px; }
.scope-chip { margin-left: auto; }

/* ============ Upgrade: notes, insights, runner, catalog ============ */
.note-area {
  width: 100%; font: inherit; font-size: 14px; line-height: 1.6; color: var(--ink);
  background: var(--bg-sunk); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 12px 14px; resize: vertical; min-height: 180px;
}
.notes-hint { font-size: 12.5px; color: var(--ink-faint); margin: 4px 0 10px; }
.run-out {
  margin: 0 !important; border-top: 1px dashed var(--border) !important;
  border-radius: 0 0 var(--radius) var(--radius) !important;
  font-size: 12.5px !important; color: var(--ok); background: var(--bg-sunk) !important;
  max-height: 220px; overflow: auto;
}
.spark { display: flex; align-items: flex-end; gap: 5px; height: 70px; padding: 4px 2px; }
.spark span { flex: 1; max-width: 26px; background: var(--bg-sunk); border-radius: 3px 3px 0 0; }
.spark span.on { background: linear-gradient(180deg, var(--accent-2), var(--accent)); }
.cat-chips { margin: 0 0 14px; flex-wrap: wrap; }

/* ============ Courses mega menu ============ */
.mega-wrap { position: relative; }
.courses-btn {
  display: flex; align-items: center; gap: 6px; font: inherit; font-size: 13.5px; font-weight: 600;
  color: var(--ink); cursor: pointer; background: var(--bg-sunk);
  border: 1px solid var(--border); border-radius: 999px; padding: 6px 14px;
  transition: border-color var(--ease), background var(--ease);
}
.courses-btn:hover, .courses-btn[aria-expanded="true"] { border-color: var(--accent); color: var(--accent); }
.courses-btn .chev { transition: transform var(--ease); }
.courses-btn[aria-expanded="true"] .chev { transform: rotate(180deg); }
.mega {
  position: absolute; top: calc(100% + 10px); left: 0; z-index: 90;
  width: min(760px, calc(100vw - 28px));
  background: var(--bg-raise); border: 1px solid var(--border); border-radius: var(--radius-lg);
  box-shadow: var(--shadow); padding: 18px;
  opacity: 0; transform: translateY(-6px); transition: opacity var(--ease), transform var(--ease);
}
.mega[data-open] { opacity: 1; transform: none; }
.mega-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 4px 18px; }
.mega-col h4 {
  display: flex; align-items: center; gap: 7px; margin: 10px 0 4px;
  font-size: 11px; text-transform: uppercase; letter-spacing: .08em; color: var(--ink-faint);
}
.mega-col h4 svg { color: var(--accent); }
.mega-item {
  display: flex; align-items: center; gap: 10px; padding: 8px 10px; border-radius: var(--radius);
  text-decoration: none; color: var(--ink); transition: background var(--ease), transform var(--ease);
}
.mega-item:hover, .mega-item:focus-visible { background: var(--accent-soft); transform: translateX(2px); }
.mega-item .ring { flex: none; }
.mega-item-text { display: flex; flex-direction: column; line-height: 1.3; min-width: 0; }
.mega-item-text strong { font-size: 13.5px; font-weight: 600; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.mega-item-text small { font-size: 11.5px; color: var(--ink-faint); }
.mega-foot {
  grid-column: 1 / -1; display: flex; gap: 18px; margin-top: 12px; padding-top: 12px;
  border-top: 1px solid var(--border); font-size: 13px;
}
.mega-foot a { color: var(--accent); text-decoration: none; font-weight: 600; }
.mega-foot a:hover { text-decoration: underline; }
@media (max-width: 880px) {
  .mega-wrap { position: static; }
  .mega {
    position: fixed; left: 10px; right: 10px; top: calc(var(--topbar-h) + 6px);
    width: auto; max-height: calc(100vh - var(--topbar-h) - 20px); overflow-y: auto;
  }
  .courses-btn { padding: 6px 10px; }
}

/* ============ Sidebar v2 — course card, foldable groups, aligned dots ============ */
.sidebar { padding: 12px 10px 48px; scrollbar-width: thin; scrollbar-color: var(--border) transparent; }
.sidebar-filter { position: sticky; top: 0; z-index: 5; background: var(--bg); padding: 2px 4px 10px; }
#nav-filter { border-radius: 999px; padding: 7px 14px; }
#nav-filter:focus { border-color: var(--accent); outline: none; box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 16%, transparent); }

.nav-back {
  display: inline-flex; align-items: center; gap: 4px; font-size: 12px; color: var(--ink-faint);
  text-decoration: none; padding: 4px 12px; margin: 0 2px 10px; border: 1px solid var(--border);
  border-radius: 999px; background: var(--bg-raise); transition: color var(--ease), border-color var(--ease);
}
.nav-back:hover { color: var(--accent); border-color: var(--accent); }

.nav-course-card {
  display: block; margin: 0 2px 14px; padding: 13px 15px; border-radius: var(--radius-lg);
  text-decoration: none; color: var(--ink);
  background: linear-gradient(135deg, var(--accent-soft), color-mix(in srgb, var(--accent-soft) 35%, var(--bg-raise)));
  border: 1px solid color-mix(in srgb, var(--accent) 28%, var(--border));
  transition: border-color var(--ease);
}
.nav-course-card:hover { border-color: var(--accent); }
.nav-course-card strong { font-size: 14.5px; line-height: 1.3; display: block; margin-bottom: 9px; letter-spacing: -.01em; }
.ncc-bar { display: block; height: 5px; border-radius: 3px; background: color-mix(in srgb, var(--accent) 14%, var(--bg-sunk)); overflow: hidden; }
.ncc-bar i { display: block; height: 100%; width: 0; border-radius: 3px; background: linear-gradient(90deg, var(--accent), var(--accent-2)); transition: width .5s ease; }
.ncc-meta { display: block; margin-top: 7px; font-size: 11px; color: var(--ink-soft); font-variant-numeric: tabular-nums; }

.nav-group { margin: 2px 0; }
.nav-group-h {
  display: flex; align-items: center; gap: 8px; width: 100%; cursor: pointer;
  font: inherit; font-size: 10.5px; font-weight: 700; letter-spacing: .09em; text-transform: uppercase;
  color: var(--ink-faint); background: none; border: none; padding: 12px 8px 5px; text-align: left;
}
.nav-group-h:hover .g-title { color: var(--accent); }
.g-title { transition: color var(--ease); }
.g-count {
  margin-left: auto; font-size: 10px; font-weight: 600; color: var(--ink-faint);
  background: var(--bg-sunk); border-radius: 999px; padding: 1px 7px; font-variant-numeric: tabular-nums;
}
.g-count.g-done { color: var(--ok); background: var(--ok-soft); }
.g-chev { flex: none; transition: transform var(--ease); }
.is-folded .g-chev { transform: rotate(-90deg); }
.is-folded .nav-group-items { display: none; }
#nav-tree.filtering .nav-group-items { display: block !important; }
.nav-group-items { border-left: 1px solid var(--border); margin-left: 12px; padding-left: 7px; }

.nav-item {
  display: flex; align-items: flex-start; gap: 9px; text-decoration: none;
  color: var(--ink-soft); font-size: 13px; line-height: 1.4; padding: 6px 8px; margin: 1px 0;
  border-radius: 8px; border-left: none;
  transition: background var(--ease), color var(--ease);
}
.nav-item:hover { background: var(--bg-sunk); color: var(--ink); }
.nav-item.is-active { color: var(--accent); background: var(--accent-soft); font-weight: 600; border-left: none; }
.ni-title { flex: 1; min-width: 0; }
.nav-item .dot {
  flex: none; width: 12px; height: 12px; margin-top: 3px; border-radius: 50%;
  border: 1.5px solid color-mix(in srgb, var(--ink-faint) 60%, transparent);
  display: flex; align-items: center; justify-content: center;
  font-size: 8px; line-height: 1; color: transparent; background: transparent;
  transition: background var(--ease), border-color var(--ease);
}
.nav-item.in-progress .dot { border-color: var(--accent); background: radial-gradient(circle, var(--accent) 0 2.5px, transparent 3px); }
.nav-item.is-done .dot { background: var(--ok); border-color: var(--ok); color: #fff; }
.nav-item.is-done .dot::before { content: '✓'; font-weight: 700; }
.nav-item .mins {
  flex: none; margin-left: 4px; margin-top: 2px; font-size: 10px; color: var(--ink-faint);
  background: var(--bg-sunk); padding: 1px 6px; border-radius: 999px; font-variant-numeric: tabular-nums;
}
.nav-item.is-active .mins { background: color-mix(in srgb, var(--accent) 14%, var(--bg-sunk)); color: var(--accent); }
.sidebar::-webkit-scrollbar { width: 8px; }
.sidebar::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }

/* ============ Responsive v2 — phones, tablets, touch, safe areas ============ */
* { -webkit-tap-highlight-color: transparent; }
body.nav-open { overflow: hidden; }

/* Safe areas (notched phones) */
.topbar { padding-left: max(14px, env(safe-area-inset-left)); padding-right: max(14px, env(safe-area-inset-right)); }
#toast { bottom: max(22px, env(safe-area-inset-bottom)); }

/* Dynamic viewport height: keeps drawer + rails correct when mobile URL bar collapses */
.sidebar, .toc { height: calc(100dvh - var(--topbar-h)); }

/* Tablet (880–1150px): trim the sidebar so content keeps room */
@media (max-width: 1150px) {
  :root { --sidebar-w: 248px; }
}

/* Phone & small tablet */
@media (max-width: 880px) {
  .sidebar { height: calc(100dvh - var(--topbar-h)); padding-bottom: max(48px, env(safe-area-inset-bottom)); }
  /* iOS zooms on inputs under 16px — keep all inputs at 16px on touch layouts */
  #nav-filter, #search-input, .note-area { font-size: 16px; }
  /* Search becomes a full-height sheet */
  .modal { padding: 0; align-items: stretch; }
  .modal-box { max-width: none; max-height: none; height: 100dvh; border-radius: 0; border: none; padding-top: max(14px, env(safe-area-inset-top)); }
  #search-results { padding-bottom: 40px; }
  /* Content typography */
  .md h1 { font-size: 24px; }
  .md h2 { font-size: 19px; margin-top: 32px; }
  .md pre { font-size: 12px; padding: 12px; }
  .hero { gap: 16px; }
  .hero .ring { width: 92px; height: 92px; }
  .pager { flex-direction: column; }
  .flash { padding: 18px 16px; }
  .flash-actions .btn { flex: 1; text-align: center; }
  .page-tools { gap: 6px; }
}

/* Small phones */
@media (max-width: 560px) {
  .content { padding: calc(var(--topbar-h) + 14px) 14px 56px; }
  .brand-text { display: none; }                /* logo mark stays */
  #practice-link, #help-open { display: none; } /* reachable from home + ? shortcut on desktop */
  .search-trigger { min-width: 0; padding: 6px 10px; }
  .search-trigger kbd { display: none; }
  .courses-btn { font-size: 12.5px; padding: 6px 10px; }
  .cards { grid-template-columns: 1fr; }
  .course-grid { grid-template-columns: 1fr; }
  .path-row { flex-wrap: wrap; gap: 6px 12px; }
  .path-row .name { width: 100%; }
  .shortcuts { grid-template-columns: 1fr; }
  .toc { display: none; }
}

/* Touch devices: comfortable ≥40px targets regardless of width */
@media (pointer: coarse) {
  .nav-item { padding: 10px 8px; }
  .nav-group-h { padding: 14px 8px 6px; }
  .tool-btn { padding: 8px 14px; }
  .icon-btn { padding: 9px 12px; }
  .courses-btn { padding: 9px 14px; }
  .mega-item { padding: 12px 10px; }
  .copy-btn { padding: 6px 10px; }
  #search-results li { padding: 12px; }
  .lang-tabs [role="tab"] { padding: 9px 16px; }
  .sec-toggle { padding: 4px 10px; }
}

/* Landscape phones: reclaim vertical space */
@media (max-height: 480px) and (orientation: landscape) {
  :root { --topbar-h: 48px; }
  .hero .ring { width: 72px; height: 72px; }
}

/* ============ Redesign pass 1: identity, hero, cards ============ */
/* Ambient depth: faint accent glow at the top of the page */
html[data-theme="dark"] body { background: radial-gradient(900px 420px at 62% -140px, rgba(99,102,241,.16), transparent 70%), var(--bg); }
html[data-theme="light"] body { background: radial-gradient(900px 420px at 62% -140px, rgba(99,102,241,.07), transparent 70%), var(--bg); }

/* Category chip: colored identity square (hue set via --h) */
.cat-chip {
  flex: none; display: inline-flex; align-items: center; justify-content: center;
  width: 38px; height: 38px; border-radius: 11px;
  color: hsl(var(--h, 243) 75% 62%);
  background: hsl(var(--h, 243) 75% 62% / .13);
  border: 1px solid hsl(var(--h, 243) 75% 62% / .25);
}
.recent-card .cat-chip, .nav-home-item .cat-chip { width: 30px; height: 30px; border-radius: 9px; }

/* Hero */
.hero-home { align-items: center; justify-content: space-between; }
.hero-copy { max-width: 60ch; }
.hero-home h1 { font-size: 32px; letter-spacing: -.02em; margin-bottom: 8px; }
.stat-chips { display: flex; gap: 8px; margin-top: 16px; flex-wrap: wrap; }
.stat-chip {
  font-size: 12.5px; color: var(--ink-soft); background: var(--bg-raise);
  border: 1px solid var(--border); border-radius: 999px; padding: 5px 13px;
}
.stat-chip b { color: var(--ink); font-weight: 700; margin-right: 2px; }
.stat-chip.is-warn { border-color: hsl(38 90% 55% / .5); color: hsl(38 80% 45%); }
html[data-theme="dark"] .stat-chip.is-warn { color: hsl(38 90% 65%); }

/* Card system: real elevation + hover */
.card { box-shadow: 0 1px 2px rgba(0,0,0,.06); }
a.card:hover { transform: translateY(-2px); box-shadow: 0 8px 24px rgba(20,20,50,.12); }
html[data-theme="dark"] .card { box-shadow: 0 1px 3px rgba(0,0,0,.35); }
html[data-theme="dark"] a.card:hover { box-shadow: 0 10px 30px rgba(0,0,0,.45); }

/* Action cards */
.ac-kicker {
  display: block; font-size: 10.5px; font-weight: 700; letter-spacing: .08em;
  text-transform: uppercase; color: var(--accent); margin-bottom: 6px;
}
.action-card h3 { font-size: 15.5px; }

/* Recent cards: icon + text row */
.recent-card { display: flex; align-items: center; gap: 12px; }
.recent-card h3 { font-size: 13.5px; margin: 0; }
.recent-card p { font-size: 11.5px; margin: 2px 0 0; }

/* Course cards v2 */
.cc2 { display: flex; flex-direction: column; gap: 10px; padding: 18px; }
.cc2:hover { border-color: hsl(var(--h, 243) 70% 60% / .55); }
.cc2-top { display: flex; gap: 12px; align-items: center; }
.cc2-head h3 { margin: 0; font-size: 15.5px; letter-spacing: -.01em; }
.cc2-cat { font-size: 11px; color: hsl(var(--h, 243) 60% 58%); font-weight: 600; }
.cc2-tag { margin: 0; font-size: 12.5px; color: var(--ink-soft); line-height: 1.5; flex: 1; }
.cc2-meta { display: flex; gap: 6px; flex-wrap: wrap; }
.cc2-meta span {
  font-size: 10.5px; color: var(--ink-faint); background: var(--bg-sunk);
  border-radius: 999px; padding: 2px 9px; font-variant-numeric: tabular-nums;
}
.cc2-foot { display: flex; align-items: center; gap: 10px; }
.cc2-foot .bar { height: 5px; }
.cc2-foot .bar i { background: linear-gradient(90deg, hsl(var(--h,243) 70% 58%), hsl(var(--h,243) 80% 70%)); }
.cc2-pct { font-size: 11px; font-weight: 700; color: var(--ink-faint); min-width: 34px; text-align: right; font-variant-numeric: tabular-nums; }

/* Home sidebar: icon rows */
.nav-home-item { align-items: center; padding: 7px 8px; }
.nav-home-item .nhi-ico {
  flex: none; display: inline-flex; align-items: center; justify-content: center;
  width: 30px; height: 30px; border-radius: 9px; color: var(--accent);
  background: var(--accent-soft); border: 1px solid color-mix(in srgb, var(--accent) 25%, transparent);
}
.nav-home-item .ni-title { font-size: 13.5px; }

/* Topbar polish */
.top-actions { gap: 2px; }
.top-actions .icon-btn { min-width: 34px; text-align: center; }
.top-actions::before { content: ''; width: 1px; height: 18px; background: var(--border); margin: 0 8px 0 4px; }
.hero-chip { width: 84px; height: 84px; border-radius: 22px; }