:root, :root[data-theme="dark"] {
  --bg: #121212; --bg2: #1a1a1a; --card: #1e1e1e; --line: #2e2e2e; --text: #ececec; --muted: #9a9a9a;
  --amber: #f2a93b; --amber-ink: #1a1206; --good: #5bc48a; --goodbg: rgba(91,196,138,.1); --bad: #ef6b5b; --badbg: rgba(239,107,91,.1);
  --shadow: none;
}
:root[data-theme="light"] {
  --bg: #f6f4ef; --bg2: #ffffff; --card: #ffffff; --line: #e1ddd3; --text: #1b1b1b; --muted: #6b675f;
  --amber: #c77a0a; --amber-ink: #ffffff; --good: #1f8a4c; --goodbg: rgba(31,138,76,.08); --bad: #c0392b; --badbg: rgba(192,57,43,.07);
}
* { box-sizing: border-box; }
html, body { margin: 0; background: var(--bg); color: var(--text); }
body { font: 16px/1.6 Inter, system-ui, sans-serif; -webkit-font-smoothing: antialiased; }
h1, h2, h3, .brand, .kicker, .btn, .unum, .ring b, .stats b, .big { font-family: 'Space Grotesk', Inter, sans-serif; }
h1 { font-size: clamp(26px, 4vw, 38px); line-height: 1.15; margin: 6px 0 14px; letter-spacing: -.01em; }
h2 { font-size: 22px; margin: 32px 0 10px; }
h3 { font-size: 18px; margin: 22px 0 8px; }
a { color: var(--amber); }
.muted { color: var(--muted); }
.small { font-size: 14px; }
.hide { display: none !important; }
.kicker { color: var(--amber); font-size: 13px; letter-spacing: .12em; text-transform: uppercase; font-weight: 600; }
.lead { font-size: 18px; color: var(--muted); max-width: 720px; }
.sec { border-bottom: 1px solid var(--line); padding-bottom: 6px; }

/* shell */
.top { position: sticky; top: 0; z-index: 20; display: flex; align-items: center; gap: 14px; padding: 10px 18px; background: var(--bg); border-bottom: 1px solid var(--line); }
.brand { color: var(--text); text-decoration: none; font-weight: 700; font-size: 18px; }
.brand .mark { color: var(--amber); }
.topstats { margin-left: auto; display: flex; gap: 14px; font-size: 13px; color: var(--muted); }
.topstats .hot, .hot b { color: var(--amber); }
.sync { font-size: 12px; color: var(--muted); }
.iconbtn { background: none; border: 1px solid var(--line); color: var(--text); width: 36px; height: 36px; font-size: 16px; cursor: pointer; }
#menubtn { display: none; }
.wrap { display: flex; max-width: 1180px; margin: 0 auto; }
nav.side { width: 200px; flex: none; padding: 24px 12px; position: sticky; top: 57px; align-self: flex-start; }
nav.side a { display: block; padding: 8px 12px; color: var(--text); text-decoration: none; border-left: 2px solid transparent; }
nav.side a:hover { background: var(--bg2); }
nav.side a.on { border-left-color: var(--amber); color: var(--amber); }
.navlbl { font-size: 11px; letter-spacing: .12em; text-transform: uppercase; color: var(--muted); padding: 18px 12px 4px; }
main { flex: 1; min-width: 0; padding: 28px 24px 120px; max-width: 900px; }

/* buttons */
.btn { display: inline-flex; align-items: center; gap: 6px; padding: 10px 16px; background: var(--bg2); color: var(--text); border: 1px solid var(--line); cursor: pointer; font-size: 15px; font-weight: 600; text-decoration: none; }
.btn:hover:not(:disabled) { border-color: var(--amber); }
.btn:disabled { opacity: .45; cursor: not-allowed; }
.btn.primary { background: var(--amber); color: var(--amber-ink); border-color: var(--amber); }
.btn.ghost { background: transparent; }
.btn.big { padding: 13px 20px; font-size: 16px; }
.btn.small { padding: 6px 10px; font-size: 13px; }
.row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; margin: 16px 0; }
.row.center { justify-content: center; }
.back { display: inline-block; margin-bottom: 16px; color: var(--muted); text-decoration: none; font-size: 14px; }
.chip { background: var(--bg2); border: 1px solid var(--line); color: var(--text); padding: 6px 12px; font-size: 13px; cursor: pointer; margin: 0 6px 6px 0; }
.chip.on { background: var(--amber); color: var(--amber-ink); border-color: var(--amber); }
.pill { font-size: 11px; padding: 1px 7px; border: 1px solid var(--line); color: var(--muted); text-transform: uppercase; letter-spacing: .06em; }
.pill.free { color: var(--good); border-color: var(--good); }
input, textarea, select { font: inherit; color: var(--text); background: var(--bg2); border: 1px solid var(--line); padding: 10px 12px; }
input:focus, textarea:focus { outline: 2px solid var(--amber); outline-offset: -1px; }

/* enroll + dashboard */
.hero { padding: 40px 0; }
.enroll { display: flex; gap: 12px; align-items: flex-end; flex-wrap: wrap; margin: 26px 0 10px; }
.enroll label { display: flex; flex-direction: column; gap: 6px; font-size: 14px; color: var(--muted); }
.dash { border: 1px solid var(--line); background: var(--card); padding: 26px; }
.dashtop { display: flex; gap: 24px; justify-content: space-between; align-items: center; flex-wrap: wrap; }
.dashtop .btn { margin-top: 6px; }
.ring { --p: 0; width: 120px; height: 120px; border-radius: 50%; background: conic-gradient(var(--amber) calc(var(--p) * 1%), var(--line) 0); display: grid; place-items: center; flex: none; }
.ring > div { width: 96px; height: 96px; border-radius: 50%; background: var(--card); display: grid; place-content: center; text-align: center; }
.ring b { font-size: 26px; }
.ring span { font-size: 12px; color: var(--muted); }
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1px; background: var(--line); margin-top: 24px; border: 1px solid var(--line); }
.stats > * { background: var(--card); padding: 14px; text-decoration: none; color: var(--text); }
.stats b { display: block; font-size: 20px; }
.stats span { font-size: 13px; color: var(--muted); }
.map { display: grid; grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); gap: 14px; }
.unitcard { display: flex; flex-direction: column; gap: 6px; padding: 18px; border: 1px solid var(--line); background: var(--card); text-decoration: none; color: var(--text); transition: border-color .15s; }
.unitcard:hover { border-color: var(--amber); }
.unitcard.locked { opacity: .5; cursor: not-allowed; }
.unitcard.locked:hover { border-color: var(--line); }
.unitcard.passed { border-left: 3px solid var(--good); }
.unitcard.final { border-style: dashed; }
.unum { font-size: 12px; letter-spacing: .1em; text-transform: uppercase; color: var(--amber); }
.utitle { font-weight: 600; font-size: 17px; line-height: 1.3; }
.usum { font-size: 14px; color: var(--muted); flex: 1; }
.ubar { height: 4px; background: var(--line); }
.ubar i { display: block; height: 100%; background: var(--amber); }
.ustat { font-size: 13px; color: var(--muted); }

/* unit + lesson */
.goals { border: 1px solid var(--line); background: var(--card); padding: 16px 20px; margin: 18px 0; }
.goalhead { font-weight: 600; margin-bottom: 4px; }
.goals ul { margin: 0; padding-left: 20px; }
.lessons { display: flex; flex-direction: column; border: 1px solid var(--line); }
.lrow { display: flex; gap: 14px; align-items: center; padding: 14px 16px; border-bottom: 1px solid var(--line); text-decoration: none; color: var(--text); background: var(--card); }
.lrow:last-child { border-bottom: 0; }
.lrow:hover { background: var(--bg2); }
.lrow.locked { opacity: .45; cursor: not-allowed; }
.lnum { width: 30px; height: 30px; flex: none; display: grid; place-items: center; border: 1px solid var(--line); font-size: 14px; font-weight: 600; }
.lrow.done .lnum { background: var(--good); color: #fff; border-color: var(--good); }
.lrow.exam .lnum { border-color: var(--amber); color: var(--amber); }
.lrow.exam.done .lnum { color: #fff; }
.ltitle { flex: 1; }
.lmin { font-size: 13px; color: var(--muted); }
.reslist { padding-left: 20px; }
.reslist li { margin-bottom: 10px; }

.prose { font-size: 17px; line-height: 1.7; }
.prose h2 { font-size: 22px; }
.prose h3 { font-size: 18px; }
.prose table { width: 100%; border-collapse: collapse; margin: 16px 0; font-size: 15px; display: block; overflow-x: auto; }
.prose th, .prose td { border: 1px solid var(--line); padding: 8px 10px; text-align: left; vertical-align: top; }
.prose th { background: var(--bg2); }
.prose code, .msg code { background: var(--bg2); padding: 1px 5px; font-size: .92em; }
.prose blockquote { margin: 16px 0; padding: 4px 18px; border-left: 3px solid var(--line); color: var(--muted); }
.callout { border: 1px solid var(--line); border-left: 4px solid var(--amber); background: var(--card); padding: 14px 18px; margin: 20px 0; }
.callout > b:first-child, .callout .ch { display: block; font-family: 'Space Grotesk', sans-serif; margin-bottom: 4px; }
.callout.tip { border-left-color: var(--good); }
.callout.warn { border-left-color: var(--bad); }
.callout.mi { border-left-color: #4a90d9; }
.callout p:last-child { margin-bottom: 0; }
.example { border: 1px dashed var(--line); background: var(--bg2); padding: 14px 18px; margin: 20px 0; }
.example .eh { font-family: 'Space Grotesk', sans-serif; font-weight: 600; color: var(--amber); margin-bottom: 6px; }
.formula { font-family: 'Space Grotesk', sans-serif; font-size: 20px; text-align: center; padding: 16px; border: 1px solid var(--line); background: var(--card); margin: 18px 0; }
.lessonfoot { display: flex; gap: 16px; align-items: center; margin: 30px 0 12px; }
#after { margin: 10px 0; }

/* calculators */
.calc { border: 1px solid var(--amber); background: var(--card); padding: 16px; margin: 22px 0; }
.calchead { font-family: 'Space Grotesk', sans-serif; font-weight: 600; margin-bottom: 10px; }
.calchead span { font-weight: 400; font-size: 13px; color: var(--muted); margin-left: 6px; }
.calcgrid { display: grid; grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); gap: 10px; }
.calcgrid label { display: flex; flex-direction: column; font-size: 13px; color: var(--muted); gap: 4px; }
.calcgrid input { width: 100%; }
.calcout { display: grid; grid-template-columns: repeat(auto-fill, minmax(180px, 1fr)); gap: 1px; background: var(--line); margin-top: 12px; border: 1px solid var(--line); }
.calcout div { background: var(--bg2); padding: 10px 12px; }
.calcout span { display: block; font-size: 12px; color: var(--muted); }
.calcout b { font-size: 18px; font-family: 'Space Grotesk', sans-serif; }

/* questions */
.qcard { border: 1px solid var(--line); background: var(--card); padding: 20px; margin: 14px 0; }
.qcard.right { border-color: var(--good); }
.qtag { font-size: 12px; color: var(--amber); text-transform: uppercase; letter-spacing: .08em; margin-bottom: 6px; }
.qtext { font-size: 17px; margin-bottom: 14px; }
.choices { display: flex; flex-direction: column; gap: 8px; }
.choice { text-align: left; font: inherit; padding: 12px 14px; background: var(--bg2); color: var(--text); border: 1px solid var(--line); cursor: pointer; }
.choice:hover:not(:disabled) { border-color: var(--amber); }
.choice.x { border-color: var(--bad); background: var(--badbg); text-decoration: line-through; opacity: .8; }
.choice.ok { border-color: var(--good); background: var(--goodbg); }
.choice:disabled { cursor: default; }
.numform { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.numin { width: 220px; font-size: 18px; }
.unitlbl { color: var(--muted); font-size: 14px; }
.fb:empty { display: none; }
.fb { margin-top: 14px; }
.good { border-left: 3px solid var(--good); background: var(--goodbg); padding: 12px 16px; }
.bad { border-left: 3px solid var(--bad); background: var(--badbg); padding: 12px 16px; }
.good p:last-child, .bad p:last-child { margin-bottom: 0; }
.ans { font-size: 17px; }
.walk { margin: 12px 0; border: 1px solid var(--line); background: var(--bg2); padding: 12px 16px; }
.walkhead { font-weight: 600; font-family: 'Space Grotesk', sans-serif; }
.walk ol { margin: 8px 0; padding-left: 22px; }
.walk li { display: none; margin-bottom: 6px; }
.walk li.show { display: list-item; animation: fade .25s; }
@keyframes fade { from { opacity: 0; transform: translateY(-3px); } to { opacity: 1; } }
.fbtools { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 10px; }

/* exams */
.exambar { display: flex; gap: 14px; align-items: center; margin: 10px 0; font-size: 14px; color: var(--muted); }
.pbar { flex: 1; height: 6px; background: var(--line); }
.pbar i { display: block; height: 100%; background: var(--amber); transition: width .3s; }
.result { border: 1px solid var(--line); background: var(--card); padding: 28px; text-align: center; }
.result.pass { border-color: var(--good); }
.result.fail { border-color: var(--bad); }
.result .big { font-size: 56px; font-weight: 700; }
.result.pass .big { color: var(--good); }
.result.fail .big { color: var(--bad); }
.result .row { justify-content: center; }
.missed { text-align: left; }
.missed li { margin-bottom: 12px; }

/* reference */
.search { width: 100%; font-size: 17px; margin: 10px 0 20px; }
.gloss dt { font-weight: 600; font-family: 'Space Grotesk', sans-serif; margin-top: 16px; color: var(--amber); }
.gloss dd { margin: 4px 0 0; }
details.fg { border: 1px solid var(--line); background: var(--card); margin: 10px 0; }
details.fg summary { padding: 14px 18px; cursor: pointer; font-weight: 600; font-family: 'Space Grotesk', sans-serif; font-size: 17px; }
details.fg .prose { padding: 0 18px 12px; font-size: 16px; }
.panel { border: 1px solid var(--line); background: var(--card); padding: 6px 20px 16px; margin: 14px 0; }
.code { font-family: 'Space Grotesk', monospace; font-size: 24px; letter-spacing: .06em; color: var(--amber); margin: 8px 0 12px; }
.toggle { display: flex; gap: 8px; align-items: center; cursor: pointer; }
.empty { text-align: center; padding: 60px 0; }
.cert { border: 6px double var(--amber); padding: 10px; margin: 20px 0; }
.certin { border: 1px solid var(--line); padding: 50px 30px; text-align: center; }
.certin h1 { font-size: 44px; }
.drillpick { margin: 10px 0 6px; }

/* tutor */
.fab { position: fixed; right: 20px; bottom: 20px; z-index: 30; background: var(--amber); color: var(--amber-ink); border: 0; padding: 12px 18px; font: 600 15px 'Space Grotesk', sans-serif; cursor: pointer; box-shadow: 0 4px 16px rgba(0,0,0,.3); }
.drawer { position: fixed; top: 0; right: 0; bottom: 0; width: min(440px, 100vw); background: var(--bg); border-left: 1px solid var(--line); z-index: 40; transform: translateX(100%); transition: transform .2s; display: flex; flex-direction: column; }
.drawer.open { transform: none; }
.drawerhead { display: flex; justify-content: space-between; align-items: center; padding: 12px 16px; border-bottom: 1px solid var(--line); font-family: 'Space Grotesk', sans-serif; }
.drawerbody { flex: 1; display: flex; flex-direction: column; min-height: 0; padding: 12px 16px; }
.tctx { font-size: 13px; color: var(--muted); border: 1px solid var(--line); padding: 8px 10px; margin-bottom: 10px; max-height: 110px; overflow: auto; }
.tctx span { color: var(--amber); }
.tlog { flex: 1; overflow-y: auto; display: flex; flex-direction: column; gap: 10px; min-height: 200px; }
#tutorfull .tlog { max-height: 60vh; }
.msg { padding: 10px 14px; max-width: 92%; font-size: 15px; }
.msg p { margin: 0 0 8px; }
.msg p:last-child { margin: 0; }
.msg ol, .msg ul { margin: 4px 0 8px; padding-left: 20px; }
.msg.user { align-self: flex-end; background: var(--amber); color: var(--amber-ink); }
.msg.assistant { align-self: flex-start; background: var(--card); border: 1px solid var(--line); }
.msg.typing { color: var(--muted); animation: pulse 1s infinite; }
@keyframes pulse { 50% { opacity: .4; } }
.tform { display: flex; gap: 8px; margin-top: 10px; }
.tform textarea { flex: 1; resize: vertical; }
.tsuggest { margin-top: 12px; }

@media (max-width: 820px) {
  #menubtn { display: block; }
  nav.side { position: fixed; top: 57px; left: 0; bottom: 0; background: var(--bg); z-index: 25; border-right: 1px solid var(--line); transform: translateX(-100%); transition: transform .2s; }
  body.menu nav.side { transform: none; }
  main { padding: 20px 16px 110px; }
  .topstats { display: none; }
  .stats { grid-template-columns: repeat(2, 1fr); }
  .numin { width: 100%; }
  .sync { margin-left: auto; }
}
@media print {
  .top, nav.side, .fab, .drawer, .row { display: none !important; }
  main { padding: 0; }
}