:root {
  --bg: #0c1018;
  --bg-elev: #141a26;
  --bg-elev2: #1b2434;
  --border: #263246;
  --text: #e6ecf5;
  --muted: #8b9bb4;
  --accent: #4f9dff;
  --accent-dim: #2b517f;
  --good: #38c172;
  --good-dim: #1f6b41;
  --bad: #ef5350;
  --bad-dim: #7a2c2a;
  --warn: #f0b429;
  --radius: 10px;
  --maxw: 920px;
  font-synthesis: none;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  font-size: 16px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); }

/* ---------------------------------------------------------------- topbar */
.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  background: linear-gradient(180deg, #0f141f, #0c1018);
  border-bottom: 1px solid var(--border);
  padding: 14px 20px 0;
}
.brand { display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap; }
.brand .logo { color: var(--accent); font-size: 18px; }
.brand .title { font-weight: 700; font-size: 18px; letter-spacing: .3px; }
.brand .sub { color: var(--muted); font-size: 13px; }

.tabs { display: flex; gap: 4px; margin-top: 12px; flex-wrap: wrap; }
.tab {
  background: transparent;
  border: none;
  border-bottom: 2px solid transparent;
  color: var(--muted);
  padding: 9px 14px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  border-radius: 6px 6px 0 0;
}
.tab:hover { color: var(--text); background: var(--bg-elev); }
.tab.active { color: var(--text); border-bottom-color: var(--accent); }

/* ------------------------------------------------------------------ view */
.view { max-width: var(--maxw); margin: 0 auto; padding: 26px 20px 60px; }

h1 { font-size: 24px; margin: 0 0 6px; }
h2 { font-size: 19px; margin: 0 0 10px; }
.lead { color: var(--muted); margin: 0 0 22px; }

.card {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  margin-bottom: 16px;
}

.grid2 { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
@media (max-width: 640px) { .grid2 { grid-template-columns: 1fr; } }

/* ---------------------------------------------------------------- buttons */
.btn {
  background: var(--accent);
  color: #06101f;
  border: none;
  border-radius: 8px;
  padding: 11px 18px;
  font-size: 15px;
  font-weight: 700;
  cursor: pointer;
}
.btn:hover { filter: brightness(1.08); }
.btn.secondary { background: var(--bg-elev2); color: var(--text); border: 1px solid var(--border); }
.btn.ghost { background: transparent; color: var(--accent); border: 1px solid var(--accent-dim); }
.btn.danger { background: transparent; color: var(--bad); border: 1px solid var(--bad-dim); }
.btn:disabled { opacity: .45; cursor: not-allowed; }
.btn-row { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; margin-top: 14px; }

.pill {
  display: inline-block;
  background: var(--bg-elev2);
  border: 1px solid var(--border);
  color: var(--muted);
  border-radius: 999px;
  padding: 3px 11px;
  font-size: 12px;
  font-weight: 600;
}
.pill.accent { color: var(--accent); border-color: var(--accent-dim); }

/* topic chips */
.chips { display: flex; gap: 8px; flex-wrap: wrap; }
.chip {
  background: var(--bg-elev2);
  border: 1px solid var(--border);
  color: var(--text);
  border-radius: 999px;
  padding: 7px 14px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
}
.chip[aria-pressed="true"] { background: var(--accent-dim); border-color: var(--accent); color: #fff; }
.chip .n { color: var(--muted); font-weight: 500; margin-left: 5px; }

/* ----------------------------------------------------------------- quiz */
.quizbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}
.timer { font-variant-numeric: tabular-nums; font-weight: 700; font-size: 20px; }
.timer.warn { color: var(--warn); }
.timer.crit { color: var(--bad); }
.progresslabel { color: var(--muted); font-size: 14px; }

.qcount { color: var(--muted); font-size: 13px; margin-bottom: 6px; }
.qtopic { font-size: 12px; }
.stem { font-size: 17px; font-weight: 600; margin: 8px 0 16px; }

.options { display: flex; flex-direction: column; gap: 10px; }
.opt {
  display: flex;
  align-items: flex-start;
  gap: 11px;
  background: var(--bg-elev2);
  border: 1px solid var(--border);
  border-radius: 9px;
  padding: 12px 14px;
  cursor: pointer;
  text-align: left;
  color: var(--text);
  font-size: 15px;
  width: 100%;
}
.opt:hover { border-color: var(--accent-dim); }
.opt .mark {
  flex: 0 0 auto;
  width: 22px; height: 22px;
  border: 2px solid var(--muted);
  border-radius: 5px;
  display: grid; place-items: center;
  font-size: 13px; font-weight: 800;
  color: transparent;
}
.opt.radio .mark { border-radius: 50%; }
.opt[aria-pressed="true"] { border-color: var(--accent); background: #16243a; }
.opt[aria-pressed="true"] .mark { border-color: var(--accent); color: var(--accent); }

/* graded states */
.opt.correct { border-color: var(--good); background: #12281d; }
.opt.correct .mark { border-color: var(--good); color: var(--good); }
.opt.wrong { border-color: var(--bad); background: #2a1717; }
.opt.wrong .mark { border-color: var(--bad); color: var(--bad); }
.opt.reveal { border-color: var(--good-dim); }

.explain {
  margin-top: 14px;
  border-left: 3px solid var(--accent-dim);
  background: var(--bg-elev2);
  padding: 11px 14px;
  border-radius: 0 8px 8px 0;
  font-size: 14px;
  color: var(--text);
}
.explain b { color: var(--accent); }
.verdict { font-weight: 700; margin-bottom: 4px; }
.verdict.good { color: var(--good); }
.verdict.bad { color: var(--bad); }

.nav-row { display: flex; justify-content: space-between; gap: 10px; margin-top: 18px; flex-wrap: wrap; }

/* question navigator grid (exam) */
.navgrid { display: grid; grid-template-columns: repeat(auto-fill, 34px); gap: 6px; margin-top: 12px; }
.navgrid button {
  width: 34px; height: 30px;
  background: var(--bg-elev2);
  border: 1px solid var(--border);
  color: var(--muted);
  border-radius: 6px;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
}
.navgrid button.answered { color: var(--text); border-color: var(--accent-dim); }
.navgrid button.flagged { border-color: var(--warn); color: var(--warn); }
.navgrid button.current { outline: 2px solid var(--accent); }

/* ----------------------------------------------------------------- result */
.scorebig { font-size: 52px; font-weight: 800; line-height: 1; }
.scorebig.good { color: var(--good); }
.scorebig.bad { color: var(--bad); }
.bar { height: 10px; background: var(--bg-elev2); border-radius: 999px; overflow: hidden; margin: 10px 0; position: relative; }
.bar > span { display: block; height: 100%; background: var(--accent); }
.bar .passline { position: absolute; top: -3px; bottom: -3px; width: 2px; background: var(--warn); }
.topicrow { display: flex; align-items: center; gap: 10px; margin: 7px 0; font-size: 14px; }
.topicrow .name { width: 150px; text-transform: capitalize; }
.topicrow .bar { flex: 1; margin: 0; }
.topicrow .pct { width: 56px; text-align: right; color: var(--muted); font-variant-numeric: tabular-nums; }

/* flashcard */
.flash {
  min-height: 220px;
  display: grid;
  place-items: center;
  text-align: center;
  cursor: pointer;
  user-select: none;
  padding: 30px;
}
.flash .ftopic { position: absolute; top: 14px; left: 16px; }
.flash .fhint { position: absolute; bottom: 12px; right: 16px; color: var(--muted); font-size: 12px; }
.flash .front { font-size: 22px; font-weight: 700; }
.flash .back { font-size: 16px; color: var(--text); max-width: 640px; }
.cardwrap { position: relative; }

/* stat tiles */
.tiles { display: grid; grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); gap: 12px; }
.tile { background: var(--bg-elev2); border: 1px solid var(--border); border-radius: 9px; padding: 14px; }
.tile .big { font-size: 28px; font-weight: 800; }
.tile .lbl { color: var(--muted); font-size: 13px; }

table.hist { width: 100%; border-collapse: collapse; font-size: 14px; }
table.hist th, table.hist td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--border); }
table.hist th { color: var(--muted); font-weight: 600; }
.tag-pass { color: var(--good); font-weight: 700; }
.tag-fail { color: var(--bad); font-weight: 700; }

.muted { color: var(--muted); }
.center { text-align: center; }
.spacer { height: 10px; }

/* ---------------------------------------------------------------- footer */
.footer {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 18px 20px 30px;
  color: var(--muted);
  font-size: 12px;
  border-top: 1px solid var(--border);
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  align-items: center;
}
.footer .dot { opacity: .5; }