/* ============================================================================
 * Course Viewer theme. Course-agnostic. Two themes via [data-theme].
 * --accent is overridden per-course from course.json.
 * ========================================================================== */

:root {
  --accent: #6d5dfc;
  --max-read: 50rem;
  --sidebar-w: 18rem;
  --toc-w: 15rem;
  --topbar-h: 3.5rem;
  --radius: 12px;
  --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', ui-monospace, monospace;
}

[data-theme='dark'] {
  --bg: #0d0e12;
  --bg-elev: #15171e;
  --bg-elev-2: #1c1f29;
  --border: #262a37;
  --text: #e6e8ee;
  --text-dim: #9aa1b2;
  --text-faint: #6b7280;
  --code-bg: #15171e;
  --accent-soft: color-mix(in srgb, var(--accent) 18%, transparent);
}
[data-theme='light'] {
  --bg: #fbfbfd;
  --bg-elev: #ffffff;
  --bg-elev-2: #f3f4f8;
  --border: #e4e6ee;
  --text: #1a1d26;
  --text-dim: #5a6172;
  --text-faint: #9097a6;
  --code-bg: #f5f6fa;
  --accent-soft: color-mix(in srgb, var(--accent) 12%, transparent);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--topbar-h) + 1rem); }
body {
  margin: 0; background: var(--bg); color: var(--text);
  font-family: var(--font-sans); line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.skip-link {
  position: absolute; left: -999px; top: 0; z-index: 100;
  background: var(--accent); color: #fff; padding: .5rem 1rem; border-radius: 0 0 8px 0;
}
.skip-link:focus { left: 0; }

/* ---- topbar ------------------------------------------------------------- */
.topbar {
  position: sticky; top: 0; z-index: 40; height: var(--topbar-h);
  display: flex; align-items: center; gap: .75rem; padding: 0 1rem;
  background: color-mix(in srgb, var(--bg) 85%, transparent);
  backdrop-filter: blur(12px); border-bottom: 1px solid var(--border);
}
.brand { font-weight: 800; letter-spacing: -.02em; color: var(--text); font-size: 1.05rem; }
.brand:hover { text-decoration: none; }
.brand-dot { color: var(--accent); margin: 0 .15rem; }
.brand-wrap { position: relative; display: inline-flex; }
.version-hint {
  position: absolute; top: calc(100% + .4rem); left: 0; z-index: 50;
  font-family: 'JetBrains Mono', monospace; font-size: .7rem; line-height: 1;
  color: var(--text-dim); background: var(--bg);
  border: 1px solid var(--border); border-radius: .4rem; padding: .25rem .45rem;
  white-space: nowrap; opacity: 0; pointer-events: none; transition: opacity .12s ease;
}
.brand-wrap:hover .version-hint { opacity: 1; }
.topbar-spacer { flex: 1; }
.crumbs { font-size: .85rem; color: var(--text-dim); display: flex; gap: .4rem; align-items: center; overflow: hidden; white-space: nowrap; }
.crumbs a { color: var(--text-dim); }
.crumbs a:hover { color: var(--accent); }
.crumb-sep { color: var(--text-faint); }
.crumbs span:last-child { color: var(--text); font-weight: 500; text-overflow: ellipsis; overflow: hidden; }

.icon-btn {
  background: var(--bg-elev); border: 1px solid var(--border); color: var(--text);
  width: 2.25rem; height: 2.25rem; border-radius: 8px; cursor: pointer; font-size: 1rem;
  display: grid; place-items: center; transition: background .15s, border-color .15s;
}
.icon-btn:hover { background: var(--bg-elev-2); border-color: var(--accent); }
#menuToggle { display: none; }

/* ---- layout ------------------------------------------------------------- */
.layout {
  display: grid;
  grid-template-columns: var(--sidebar-w) minmax(0, 1fr) var(--toc-w);
  max-width: 90rem; margin: 0 auto; align-items: start;
}
.sidebar {
  position: sticky; top: var(--topbar-h); align-self: start;
  height: calc(100vh - var(--topbar-h)); overflow-y: auto;
  padding: 1.5rem 1rem; border-right: 1px solid var(--border);
}
.sidebar.is-hidden { display: none; }
.content {
  min-width: 0; padding: 2.5rem clamp(1rem, 4vw, 3.5rem); outline: none;
  min-height: calc(100vh - var(--topbar-h));
}
.layout:has(.sidebar.is-hidden) { grid-template-columns: 1fr; }
.layout:has(.sidebar.is-hidden) .toc { display: none; }

/* ---- sidebar nav -------------------------------------------------------- */
.nav-course { display: block; margin-bottom: 1.5rem; padding: .85rem; border-radius: var(--radius);
  background: var(--bg-elev); border: 1px solid var(--border); }
.nav-course:hover { text-decoration: none; border-color: var(--accent); }
.nav-course-kicker { display: block; font-size: .68rem; text-transform: uppercase; letter-spacing: .12em; color: var(--text-faint); }
.nav-course-title { display: block; font-weight: 700; color: var(--text); margin-top: .15rem; line-height: 1.3; }
.nav-section { margin-bottom: 1.4rem; }
.nav-section-title { font-size: .72rem; text-transform: uppercase; letter-spacing: .1em; color: var(--text-faint); font-weight: 600; margin-bottom: .5rem; padding-left: .35rem; }
.sidebar ul { list-style: none; margin: 0; padding: 0; }
.lesson-link {
  display: flex; align-items: center; gap: .55rem; padding: .4rem .55rem; border-radius: 8px;
  color: var(--text-dim); font-size: .9rem; line-height: 1.35;
}
.lesson-link:hover { background: var(--bg-elev); color: var(--text); text-decoration: none; }
.lesson-link.active { background: var(--accent-soft); color: var(--text); font-weight: 600; }
.lesson-link.active .check { border-color: var(--accent); }
.check { flex: 0 0 auto; width: .85rem; height: .85rem; border: 1.5px solid var(--border); border-radius: 50%; }
.lesson-link.done .check { background: var(--accent); border-color: var(--accent); position: relative; }
.lesson-link.done .check::after { content: '✓'; position: absolute; inset: 0; font-size: .6rem; color: #fff; display: grid; place-items: center; }
.nav-all { display: inline-block; margin-top: .5rem; font-size: .82rem; color: var(--text-dim); }

/* ---- hub ---------------------------------------------------------------- */
.hub { max-width: 64rem; margin: 0 auto; padding-top: 1rem; }
.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(20rem, 1fr)); gap: 1.25rem; }
.card {
  position: relative; display: flex; flex-direction: column; gap: .5rem; overflow: hidden;
  padding: 1.5rem; border-radius: var(--radius); background: var(--bg-elev);
  border: 1px solid var(--border); color: var(--text); transition: transform .15s, border-color .15s;
  --card-accent: var(--accent);
}
.card:hover { text-decoration: none; transform: translateY(-3px); border-color: var(--card-accent); }
.card-accent { position: absolute; inset: 0 0 auto 0; height: 4px; background: var(--card-accent); }
.card h2 { margin: .25rem 0 0; font-size: 1.3rem; letter-spacing: -.02em; }
.card-sub { margin: 0; font-size: .8rem; color: var(--card-accent); font-weight: 600; }
.card-desc { margin: .25rem 0 .5rem; color: var(--text-dim); font-size: .92rem; }
.tags { display: flex; flex-wrap: wrap; gap: .4rem; margin-top: auto; }
.tag { font-size: .72rem; padding: .2rem .55rem; border-radius: 999px; background: var(--bg-elev-2); color: var(--text-dim); border: 1px solid var(--border); }
.card-cta { margin-top: .75rem; font-weight: 600; color: var(--card-accent); font-size: .9rem; }

/* ---- document (rendered markdown) -------------------------------------- */
.doc { max-width: var(--max-read); margin: 0 auto; }
.doc > *:first-child { margin-top: 0; }
.doc h1 { font-size: clamp(1.8rem, 4vw, 2.4rem); letter-spacing: -.03em; line-height: 1.15; margin: 2.5rem 0 1rem; }
.doc h2 { font-size: 1.55rem; letter-spacing: -.02em; margin: 2.5rem 0 1rem; padding-top: .75rem; border-top: 1px solid var(--border); }
.doc h3 { font-size: 1.2rem; margin: 2rem 0 .75rem; }
.doc h4 { font-size: 1.02rem; margin: 1.5rem 0 .5rem; color: var(--text-dim); }
.doc p, .doc li { color: var(--text); }
.doc a.ext::after { content: '↗'; font-size: .75em; margin-left: .15em; color: var(--text-faint); }
.doc strong { font-weight: 700; }
.doc ul, .doc ol { padding-left: 1.4rem; }
.doc li { margin: .35rem 0; }
.doc blockquote {
  margin: 1.25rem 0; padding: .75rem 1.1rem; border-left: 3px solid var(--accent);
  background: var(--accent-soft); border-radius: 0 8px 8px 0; color: var(--text);
}
.doc blockquote p { margin: .35rem 0; }
.doc hr { border: none; border-top: 1px solid var(--border); margin: 2.5rem 0; }

.doc code {
  font-family: var(--font-mono); font-size: .86em; background: var(--bg-elev-2);
  padding: .15em .4em; border-radius: 5px; border: 1px solid var(--border);
}
.doc pre {
  background: var(--code-bg); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 1rem 1.1rem; overflow-x: auto; margin: 1.25rem 0; line-height: 1.5;
}
.doc pre code { background: none; border: none; padding: 0; font-size: .85rem; }

.doc table {
  width: 100%; border-collapse: collapse; margin: 1.5rem 0; font-size: .9rem;
  display: block; overflow-x: auto;
}
.doc th, .doc td { text-align: left; padding: .6rem .8rem; border: 1px solid var(--border); vertical-align: top; }
.doc th { background: var(--bg-elev-2); font-weight: 600; }
.doc tr:nth-child(even) td { background: var(--bg-elev); }

/* ---- lesson prev/next --------------------------------------------------- */
.lesson-nav {
  max-width: var(--max-read); margin: 3rem auto 1rem; display: flex; gap: 1rem;
  justify-content: space-between; border-top: 1px solid var(--border); padding-top: 1.5rem;
}
.ln { display: flex; flex-direction: column; gap: .15rem; padding: .85rem 1.1rem; border-radius: var(--radius);
  background: var(--bg-elev); border: 1px solid var(--border); max-width: 48%; }
.ln:hover { text-decoration: none; border-color: var(--accent); }
.ln span { font-size: .75rem; color: var(--text-faint); }
.ln strong { color: var(--text); font-size: .92rem; font-weight: 600; }
.ln.next { text-align: right; margin-left: auto; }

/* ---- table of contents -------------------------------------------------- */
.toc {
  position: sticky; top: var(--topbar-h); align-self: start;
  height: calc(100vh - var(--topbar-h)); overflow-y: auto; padding: 2.5rem 1rem;
  font-size: .82rem;
}
.toc-title { text-transform: uppercase; letter-spacing: .1em; font-size: .7rem; color: var(--text-faint); font-weight: 600; margin-bottom: .75rem; }
.toc a { display: block; padding: .25rem 0 .25rem .6rem; color: var(--text-dim); border-left: 2px solid var(--border); line-height: 1.3; }
.toc a:hover { color: var(--text); text-decoration: none; }
.toc a.active { color: var(--accent); border-left-color: var(--accent); }
.toc-h3 { padding-left: 1.4rem !important; font-size: .78rem; }

/* ---- misc --------------------------------------------------------------- */
.loading, .error { max-width: var(--max-read); margin: 3rem auto; color: var(--text-dim); }
.error h1 { color: var(--text); }
.scrim { position: fixed; inset: 0; background: rgba(0,0,0,.5); z-index: 30; }

/* ---- responsive --------------------------------------------------------- */
@media (max-width: 1100px) {
  .layout { grid-template-columns: var(--sidebar-w) minmax(0, 1fr); }
  .toc { display: none; }
}
@media (max-width: 820px) {
  #menuToggle { display: grid; }
  .crumbs { display: none; }
  .layout { grid-template-columns: 1fr; }
  .sidebar {
    position: fixed; top: var(--topbar-h); left: 0; z-index: 35; width: min(20rem, 85vw);
    background: var(--bg); transform: translateX(-105%); transition: transform .2s ease;
    border-right: 1px solid var(--border);
  }
  .sidebar.open { transform: translateX(0); }
  .sidebar.is-hidden { display: none; }
  .content { padding: 1.5rem 1.1rem; }
  .lesson-nav { flex-direction: column; }
  .ln, .ln.next { max-width: 100%; }
}