:root {
  --bg: #f7f5f0; --surface: #ffffff; --surface-2: #f0ede6; --ink: #1d2433; --muted: #5f6b7d;
  --line: #e2ddd2; --accent: #2f6fde; --accent-soft: #e4edfc; --accent-ink: #ffffff;
  --good: #1f8a5b; --good-soft: #def3e8; --bad: #c4423a; --bad-soft: #f9e1df;
  --warn: #b5701f; --warn-soft: #faedd9;
  --radius: 14px; --shadow: 0 1px 2px rgba(20, 24, 33, .06), 0 4px 14px rgba(20, 24, 33, .05);
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #14171d; --surface: #1c2028; --surface-2: #242a34; --ink: #e8eaef; --muted: #9aa3b2;
    --line: #2f3643; --accent: #6d9cf5; --accent-soft: #23314d; --accent-ink: #0f1420;
    --good: #4cc38a; --good-soft: #193628; --bad: #f07a72; --bad-soft: #3d1f1d;
    --warn: #e0a458; --warn-soft: #3a2d1a; --shadow: none; color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #14171d; --surface: #1c2028; --surface-2: #242a34; --ink: #e8eaef; --muted: #9aa3b2;
  --line: #2f3643; --accent: #6d9cf5; --accent-soft: #23314d; --accent-ink: #0f1420;
  --good: #4cc38a; --good-soft: #193628; --bad: #f07a72; --bad-soft: #3d1f1d;
  --warn: #e0a458; --warn-soft: #3a2d1a; --shadow: none; color-scheme: dark;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 17px/1.6 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
button { font: inherit; cursor: pointer; border-radius: 10px; border: 1px solid var(--line); background: var(--surface);
         color: var(--ink); padding: 9px 16px; }
button:hover { border-color: var(--accent); }
button.primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); font-weight: 600; }
button.ghost { background: transparent; border-color: transparent; }
button:disabled { opacity: .5; cursor: default; }
textarea { width: 100%; min-height: 150px; font: inherit; padding: 12px 14px; border-radius: 10px; border: 1px solid var(--line);
           background: var(--bg); color: var(--ink); resize: vertical; }
textarea:focus, button:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.topbar { position: sticky; top: 0; z-index: 5; display: flex; align-items: center; gap: 16px; padding: 12px 24px;
          background: color-mix(in srgb, var(--bg) 88%, transparent); backdrop-filter: blur(8px); border-bottom: 1px solid var(--line); }
.brand { font-weight: 750; color: var(--ink); letter-spacing: -.01em; white-space: nowrap; }
.crumbs { flex: 1; color: var(--muted); font-size: 15px; overflow: hidden; white-space: nowrap; text-overflow: ellipsis; }
.crumbs a { color: var(--muted); }
.view { max-width: 920px; margin: 0 auto; padding: 28px 24px 80px; }

h1 { font-size: 30px; line-height: 1.2; margin: 4px 0 6px; letter-spacing: -.015em; }
h2 { font-size: 22px; margin: 30px 0 10px; }
.sub { color: var(--muted); margin: 0 0 22px; }
.pill { display: inline-block; font-size: 12.5px; font-weight: 650; letter-spacing: .03em; padding: 3px 10px; border-radius: 99px;
        background: var(--surface-2); color: var(--muted); }
.pill.good { background: var(--good-soft); color: var(--good); }
.pill.bad { background: var(--bad-soft); color: var(--bad); }
.pill.warn { background: var(--warn-soft); color: var(--warn); }
.empty { padding: 36px; text-align: center; color: var(--muted); background: var(--surface); border: 1px dashed var(--line); border-radius: var(--radius); }
.empty code { background: var(--surface-2); padding: 2px 6px; border-radius: 6px; }

/* Lists of courses / weeks */
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 14px; }
.tile { display: block; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 18px 20px;
        color: var(--ink); box-shadow: var(--shadow); }
.tile:hover { border-color: var(--accent); text-decoration: none; }
.tile .code { font-weight: 750; font-size: 20px; }
.tile .muted { color: var(--muted); font-size: 14.5px; }
.weeks { display: flex; flex-direction: column; gap: 10px; }
.week { display: grid; grid-template-columns: 64px 1fr auto; gap: 16px; align-items: center; background: var(--surface);
        border: 1px solid var(--line); border-radius: var(--radius); padding: 14px 18px; color: var(--ink); }
.week:hover { border-color: var(--accent); text-decoration: none; }
.week .num { font-size: 13px; color: var(--muted); font-weight: 650; text-transform: uppercase; letter-spacing: .05em; }
.week .num b { display: block; font-size: 24px; color: var(--ink); letter-spacing: 0; }
.week .t { font-weight: 600; }
.week .topics { color: var(--muted); font-size: 14px; }
.week .right { text-align: right; display: flex; flex-direction: column; gap: 4px; align-items: flex-end; }
/* Account / sync status in the top bar */
.account { display: flex; gap: 12px; align-items: center; font-size: 14px; white-space: nowrap; }
.sync { color: var(--good); }
.sync[data-state="pending"], .sync[data-state="saving"] { color: var(--muted); }
.sync[data-state="error"] { color: var(--bad); }

/* Progress */
.bar { height: 6px; border-radius: 99px; background: var(--surface-2); overflow: hidden; margin-top: 8px; }
.bar span { display: block; height: 100%; background: var(--accent); border-radius: 99px; }
.chips { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 8px; }
.chip { font-size: 12.5px; padding: 2px 9px; border-radius: 99px; background: var(--surface-2); color: var(--muted); }
.chip.part { background: var(--accent-soft); color: var(--accent); }
.chip.done { background: var(--good-soft); color: var(--good); }
.continue { display: flex; flex-direction: column; gap: 2px; margin: 4px 0 22px; padding: 16px 20px; border-radius: var(--radius);
            background: var(--accent-soft); border: 1px solid transparent; color: var(--ink); }
.continue:hover { border-color: var(--accent); text-decoration: none; }
.continue .k { font-size: 12px; font-weight: 750; letter-spacing: .08em; text-transform: uppercase; color: var(--accent); }
.continue b { font-size: 18px; }
.continue .muted { color: var(--muted); font-size: 14.5px; }
.toolbar { display: flex; gap: 10px; flex-wrap: wrap; margin: 0 0 18px; }

/* Week tabs */
.tabs { display: flex; gap: 4px; border-bottom: 1px solid var(--line); margin: 18px 0 24px; overflow-x: auto; }
.tabs a { padding: 10px 16px; color: var(--muted); border-bottom: 2px solid transparent; margin-bottom: -1px; white-space: nowrap; font-weight: 550; }
.tabs a.on { color: var(--ink); border-color: var(--accent); }
.tabs a:hover { text-decoration: none; color: var(--ink); }
.tabs a.off { opacity: .45; pointer-events: none; }

/* Notes / summary prose */
.prose { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 30px 36px; box-shadow: var(--shadow); }
.prose h1 { font-size: 28px; } .prose h2 { font-size: 22px; border-top: 1px solid var(--line); padding-top: 22px; }
.prose h2:first-child, .prose h1 + h2 { border-top: 0; padding-top: 0; }
.prose h3 { font-size: 18.5px; margin: 22px 0 6px; }
.prose ul, .prose ol { padding-left: 24px; } .prose li { margin: 4px 0; }
.prose table { border-collapse: collapse; width: 100%; margin: 14px 0; font-size: 15.5px; display: block; overflow-x: auto; }
.prose th, .prose td { border: 1px solid var(--line); padding: 8px 12px; text-align: left; vertical-align: top; }
.prose th { background: var(--surface-2); }
.prose blockquote { margin: 16px 0; padding: 12px 18px; border-left: 4px solid var(--accent); background: var(--accent-soft); border-radius: 0 10px 10px 0; }
.prose blockquote p { margin: 4px 0; }
.prose code { background: var(--surface-2); padding: 1px 6px; border-radius: 5px; font-size: .92em; }
.prose svg { max-width: 100%; height: auto; display: block; margin: 16px auto; }
.prose .callout, .prose .example, .prose .remember, .prose .exam-tip { border-radius: 12px; padding: 14px 18px; margin: 16px 0; }
.prose .example { background: var(--warn-soft); } .prose .remember { background: var(--good-soft); } .prose .exam-tip { background: var(--bad-soft); }
.prose .example::before, .prose .remember::before, .prose .exam-tip::before { display: block; font-size: 12px; font-weight: 750;
  letter-spacing: .1em; text-transform: uppercase; margin-bottom: 4px; }
.prose .example::before { content: "Example"; color: var(--warn); }
.prose .remember::before { content: "Remember"; color: var(--good); }
.prose .exam-tip::before { content: "Exam tip"; color: var(--bad); }
.prose .example > :first-child, .prose .remember > :first-child, .prose .exam-tip > :first-child { margin-top: 0; }
.prose .example > :last-child, .prose .remember > :last-child, .prose .exam-tip > :last-child { margin-bottom: 0; }

/* Video */
.player { background: #000; border-radius: var(--radius); overflow: hidden; }
.player video { width: 100%; display: block; aspect-ratio: 16 / 9; }
.chapters { display: grid; gap: 6px; margin-top: 16px; }
.chapters button { display: flex; justify-content: space-between; text-align: left; gap: 12px; }
.chapters button.on { border-color: var(--accent); background: var(--accent-soft); }
.chapters .time { color: var(--muted); font-variant-numeric: tabular-nums; }
.speed { display: flex; gap: 6px; align-items: center; margin-top: 12px; color: var(--muted); font-size: 14px; flex-wrap: wrap; }
.speed button { padding: 5px 10px; font-size: 14px; } .speed button.on { border-color: var(--accent); color: var(--accent); }

/* Exam */
.part-head { display: flex; justify-content: space-between; align-items: baseline; gap: 12px; flex-wrap: wrap; }
.scorebar { position: sticky; top: 56px; z-index: 3; display: flex; gap: 14px; align-items: center; justify-content: space-between;
            flex-wrap: wrap; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius);
            padding: 12px 18px; margin: 12px 0 18px; box-shadow: var(--shadow); }
.scorebar .big { font-size: 22px; font-weight: 750; font-variant-numeric: tabular-nums; }
.q { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 18px 20px; margin-bottom: 12px; }
.q .qn { font-size: 13px; color: var(--muted); font-weight: 650; display: flex; gap: 8px; align-items: center; margin-bottom: 4px; }
.q .qt { font-weight: 560; margin: 0 0 12px; white-space: pre-line; }
.opts { display: grid; gap: 8px; }
.opt { display: flex; gap: 12px; align-items: flex-start; text-align: left; width: 100%; padding: 10px 14px; background: var(--bg); }
.opt .l { flex: none; width: 26px; height: 26px; border-radius: 50%; border: 1.5px solid var(--line); display: grid; place-items: center;
          font-size: 13px; font-weight: 700; color: var(--muted); }
.opt.sel { border-color: var(--accent); background: var(--accent-soft); }
.opt.sel .l { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.marked .opt { cursor: default; }
.marked .opt.right { border-color: var(--good); background: var(--good-soft); }
.marked .opt.right .l { background: var(--good); border-color: var(--good); color: #fff; }
.marked .opt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.marked .opt.wrong .l { background: var(--bad); border-color: var(--bad); color: #fff; }
.q.is-right { border-left: 4px solid var(--good); } .q.is-wrong { border-left: 4px solid var(--bad); } .q.is-skip { border-left: 4px solid var(--warn); }
.explain { margin-top: 12px; padding: 12px 14px; border-radius: 10px; background: var(--surface-2); font-size: 15.5px; }
.explain .src { display: block; color: var(--muted); font-size: 13.5px; margin-top: 6px; }
.case { background: var(--surface-2); border-radius: 10px; padding: 12px 16px; margin: 0 0 12px; font-size: 15.5px; white-space: pre-line; }
.case b { display: block; font-size: 12px; letter-spacing: .1em; text-transform: uppercase; color: var(--muted); margin-bottom: 2px; }
.model { margin-top: 14px; border-top: 1px dashed var(--line); padding-top: 14px; }
.model h4 { margin: 0 0 6px; font-size: 13px; letter-spacing: .08em; text-transform: uppercase; color: var(--good); }
.model .ans p { margin: 6px 0; } .model .ans ul, .model .ans ol { margin: 6px 0; padding-left: 22px; }
.points { list-style: none; padding: 0; margin: 8px 0 0; display: grid; gap: 6px; }
.points label { display: flex; gap: 10px; align-items: flex-start; padding: 8px 12px; border-radius: 10px; background: var(--bg); cursor: pointer; }
.points input { margin-top: 5px; accent-color: var(--good); }
.row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; margin-top: 10px; }
.history { color: var(--muted); font-size: 14px; }
textarea[readonly] { background: var(--surface-2); color: var(--ink); }
.err { margin-top: 10px; padding: 10px 14px; border-radius: 10px; background: var(--bad-soft); color: var(--bad); font-size: 15px; }
.spin { display: inline-block; width: 13px; height: 13px; border: 2px solid currentColor; border-right-color: transparent;
        border-radius: 50%; vertical-align: -2px; margin-right: 6px; animation: spin .8s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }
.mark { margin-top: 16px; padding: 16px 18px; border-radius: 12px; background: var(--surface-2); }
.mark.stale { opacity: .6; }
.mark-head { display: flex; align-items: baseline; gap: 12px; flex-wrap: wrap; }
.mark .score { font-size: 26px; font-weight: 750; font-variant-numeric: tabular-nums; }
.mark .score.good { color: var(--good); } .mark .score.warn { color: var(--warn); } .mark .score.bad { color: var(--bad); }
.mark .feedback { margin: 8px 0 12px; }
.mpoints { list-style: none; padding: 0; margin: 0; display: grid; gap: 8px; }
.mpoints li { display: flex; gap: 12px; align-items: flex-start; padding: 10px 12px; border-radius: 10px; background: var(--surface); font-size: 15.5px; }
.mpoints .ic { flex: none; width: 26px; height: 26px; border-radius: 50%; display: grid; place-items: center; font-weight: 750; font-size: 14px; color: #fff; }
.mpoints li.full .ic { background: var(--good); } .mpoints li.partial .ic { background: var(--warn); } .mpoints li.missing .ic { background: var(--bad); }
.mpoints b { display: block; font-weight: 600; } .mpoints span:not(.ic) { color: var(--muted); }
.improve { margin-top: 12px; } .improve h4 { margin: 0 0 4px; font-size: 13px; letter-spacing: .08em; text-transform: uppercase; color: var(--accent); }
.improve ul { margin: 0; padding-left: 20px; }
.recbar { gap: 12px; }
.rec-stop { border-color: var(--bad); color: var(--bad); font-weight: 600; }
.rec-dot { display: inline-block; width: 10px; height: 10px; border-radius: 50%; background: var(--bad); margin-right: 4px;
           animation: pulse 1.2s ease-in-out infinite; }
.rec-time { font-variant-numeric: tabular-nums; font-weight: 650; color: var(--bad); }
@keyframes pulse { 50% { opacity: .25; } }
audio { width: 100%; max-width: 420px; height: 36px; }
@media (prefers-reduced-motion: reduce) { .spin, .rec-dot { animation: none; } }

@media (max-width: 640px) {
  .topbar { padding: 10px 16px; } .view { padding: 20px 16px 60px; }
  .prose { padding: 20px 18px; } h1 { font-size: 25px; }
  .week { grid-template-columns: 48px 1fr; } .week .right { grid-column: 1 / -1; flex-direction: row; align-items: center; }
  .scorebar { top: 50px; }
}
@media print {
  .topbar, .tabs, .toolbar { display: none; } body { background: #fff; } .prose { border: 0; box-shadow: none; padding: 0; }
}