/* ------------------------------------------------------------------ theme */
:root {
  --bg: #0f1116;
  --bg-elev: #171a21;
  --bg-elev-2: #1e222b;
  --border: #2a2f3a;
  --border-strong: #3a4150;
  --text: #e8eaef;
  --text-dim: #a0a7b6;
  --text-faint: #6d7484;
  --accent: #6a8dff;
  --accent-soft: rgba(106, 141, 255, 0.14);
  --good: #3ecf8e;
  --good-soft: rgba(62, 207, 142, 0.14);
  --bad: #ff6b6b;
  --bad-soft: rgba(255, 107, 107, 0.14);
  --warn: #f0b840;
  --radius: 14px;
  --radius-sm: 9px;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.35);
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #f4f5f8;
    --bg-elev: #ffffff;
    --bg-elev-2: #eef0f5;
    --border: #dfe3ec;
    --border-strong: #c6ccdb;
    --text: #171a21;
    --text-dim: #59606f;
    --text-faint: #878e9d;
    --accent: #3f63d8;
    --accent-soft: rgba(63, 99, 216, 0.1);
    --good: #14915d;
    --good-soft: rgba(20, 145, 93, 0.12);
    --bad: #d13d3d;
    --bad-soft: rgba(209, 61, 61, 0.12);
    --warn: #b07908;
    --shadow: 0 10px 30px rgba(20, 25, 40, 0.1);
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.55 system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3 { margin: 0; line-height: 1.25; font-weight: 650; letter-spacing: -0.01em; }
p { margin: 0 0 0.8em; }

/* ----------------------------------------------------------------- layout */
.app { max-width: 980px; margin: 0 auto; padding: 0 18px 80px; }

.topbar {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 0 12px;
  background: linear-gradient(var(--bg) 72%, transparent);
}
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; letter-spacing: -0.02em; }
.brand .logo {
  width: 30px; height: 30px; border-radius: 9px;
  background: linear-gradient(135deg, var(--accent), #a06aff);
  display: grid; place-items: center; color: #fff; font-size: 15px; font-weight: 800;
}
.topbar nav { display: flex; gap: 4px; margin-left: auto; flex-wrap: wrap; }

.view { display: none; animation: fade 0.18s ease; }
.view.active { display: block; }
@keyframes fade { from { opacity: 0; transform: translateY(4px); } to { opacity: 1; transform: none; } }

.section-head {
  display: flex; align-items: baseline; gap: 12px;
  flex-wrap: wrap; margin: 26px 0 14px;
}
.section-head h2 { font-size: 20px; }
.section-head .hint { color: var(--text-dim); font-size: 13px; }
.spacer { flex: 1; }

/* ------------------------------------------------------------------ atoms */
.card {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 18px;
}

button, .btn {
  font: inherit;
  font-weight: 550;
  color: var(--text);
  background: var(--bg-elev-2);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 9px 15px;
  cursor: pointer;
  transition: background 0.12s, border-color 0.12s, transform 0.06s;
}
button:hover { border-color: var(--border-strong); }
button:active { transform: translateY(1px); }
button:disabled { opacity: 0.45; cursor: not-allowed; }
button.primary { background: var(--accent); border-color: transparent; color: #fff; }
button.primary:hover { filter: brightness(1.08); }
button.ghost { background: transparent; }
button.ghost:hover { background: var(--bg-elev-2); }
button.danger { color: var(--bad); }
button.danger:hover { background: var(--bad-soft); border-color: var(--bad); }
button.tab.active { background: var(--accent-soft); border-color: transparent; color: var(--accent); }
button.big { padding: 14px 22px; font-size: 16px; }

.pill {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 3px 10px; border-radius: 999px;
  background: var(--bg-elev-2); border: 1px solid var(--border);
  font-size: 12px; color: var(--text-dim); white-space: nowrap;
}
.pill.good { color: var(--good); background: var(--good-soft); border-color: transparent; }
.pill.bad { color: var(--bad); background: var(--bad-soft); border-color: transparent; }
.pill.accent { color: var(--accent); background: var(--accent-soft); border-color: transparent; }

.bar { height: 7px; border-radius: 999px; background: var(--bg-elev-2); overflow: hidden; display: flex; }
.bar > span { display: block; height: 100%; }
.bar .ok { background: var(--good); }
.bar .no { background: var(--bad); }
.bar .neutral { background: var(--border-strong); }
.bar .seen { background: var(--accent); }

kbd {
  font: 11px/1 var(--mono);
  padding: 3px 6px; border-radius: 5px;
  background: var(--bg); border: 1px solid var(--border-strong); color: var(--text-dim);
}

.muted { color: var(--text-dim); }
.faint { color: var(--text-faint); font-size: 13px; }
.empty {
  border: 1px dashed var(--border-strong); border-radius: var(--radius);
  padding: 34px; text-align: center; color: var(--text-dim);
}

/* --------------------------------------------------------------- library */
.dropzone {
  border: 2px dashed var(--border-strong);
  border-radius: var(--radius);
  padding: 30px 20px;
  text-align: center;
  background: var(--bg-elev);
  transition: border-color 0.15s, background 0.15s;
}
.dropzone.drag { border-color: var(--accent); background: var(--accent-soft); }
.dropzone h3 { font-size: 16px; margin-bottom: 6px; }

.set-list { display: grid; gap: 12px; }
.set-card { display: grid; gap: 12px; }
.set-card .title { font-size: 17px; font-weight: 650; }
.set-card .meta { display: flex; gap: 8px; flex-wrap: wrap; }
.set-card .actions { display: flex; gap: 8px; flex-wrap: wrap; }

/* ----------------------------------------------------------------- setup */
.setup-grid { display: grid; gap: 16px; grid-template-columns: 1fr; }
.options { display: grid; gap: 10px; }
.option-row { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }
.option-row > .label { min-width: 96px; color: var(--text-dim); font-size: 13px; }
.toggle {
  display: flex; align-items: center; gap: 8px; cursor: pointer;
  padding: 5px 9px; border-radius: var(--radius-sm); border: 1px solid transparent;
}
.toggle:hover { background: var(--bg-elev-2); }
.toggle:has(input:checked) { border-color: var(--border-strong); background: var(--accent-soft); }
.toggle .faint { font-size: 12px; }
@media (max-width: 620px) { .toggle .faint { display: none; } }

.tree { display: grid; gap: 8px; }
.tree-cat {
  border: 1px solid var(--border); border-radius: var(--radius-sm);
  background: var(--bg-elev); overflow: hidden;
}
.tree-cat > header {
  display: flex; align-items: center; gap: 10px; padding: 11px 13px; cursor: pointer;
}
.tree-cat > header:hover { background: var(--bg-elev-2); }
.tree-cat .cat-title { font-weight: 600; flex: 1; min-width: 0; }
.tree-cat .bar { width: 110px; flex: none; }
.tree-cat .twist { color: var(--text-faint); transition: transform 0.15s; font-size: 12px; }
.tree-cat.open .twist { transform: rotate(90deg); }
.tree-subs { display: none; padding: 2px 13px 12px 40px; }
.tree-cat.open .tree-subs { display: grid; gap: 2px; }
.tree-subs label {
  display: flex; align-items: center; gap: 9px; padding: 5px 6px;
  border-radius: 7px; cursor: pointer; font-size: 14px;
}
.tree-subs label:hover { background: var(--bg-elev-2); }
.tree-subs .count { margin-left: auto; color: var(--text-faint); font-size: 12px; font-family: var(--mono); }
input[type="checkbox"] { width: 16px; height: 16px; accent-color: var(--accent); cursor: pointer; }

select, input[type="number"] {
  font: inherit; color: var(--text); background: var(--bg-elev-2);
  border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 8px 11px;
}

.start-bar {
  position: sticky; bottom: 0; margin-top: 16px;
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
  padding: 13px; border-radius: var(--radius);
  background: var(--bg-elev); border: 1px solid var(--border); box-shadow: var(--shadow);
}

/* -------------------------------------------------------------- practice */
.practice-head { display: grid; gap: 10px; margin: 8px 0 18px; }
.practice-head .row { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.progress { height: 6px; border-radius: 999px; background: var(--bg-elev-2); overflow: hidden; }
.progress > span { display: block; height: 100%; background: var(--accent); transition: width 0.25s ease; }
.counter { font-family: var(--mono); font-size: 13px; }

.flashcard {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: 18px;
  box-shadow: var(--shadow);
  padding: 26px;
  min-height: 260px;
  display: flex; flex-direction: column; gap: 18px;
}
.flashcard .crumbs { display: flex; gap: 8px; flex-wrap: wrap; }
.flashcard .question {
  font-size: clamp(20px, 3vw, 26px); font-weight: 600; letter-spacing: -0.015em;
  white-space: pre-wrap;
}
.flashcard .answer {
  border-top: 1px solid var(--border); padding-top: 18px;
  font-size: 17px; color: var(--text);
  animation: reveal 0.22s ease;
}
.flashcard .answer > div { white-space: pre-wrap; }
.flashcard .answer .lbl {
  display: block; font-size: 11px; letter-spacing: 0.09em; text-transform: uppercase;
  color: var(--text-faint); margin-bottom: 7px;
}
@keyframes reveal { from { opacity: 0; transform: translateY(-6px); } to { opacity: 1; transform: none; } }

.card-actions { margin-top: auto; display: flex; gap: 10px; flex-wrap: wrap; align-items: center; }
.judge { display: flex; gap: 10px; flex: 1; }
.judge button { flex: 1; display: flex; justify-content: center; align-items: center; gap: 9px; }
button.correct { background: var(--good-soft); border-color: var(--good); color: var(--good); }
button.correct:hover { background: var(--good); color: #06130d; }
button.wrong { background: var(--bad-soft); border-color: var(--bad); color: var(--bad); }
button.wrong:hover { background: var(--bad); color: #210909; }

.keyhints { display: flex; gap: 14px; flex-wrap: wrap; margin-top: 14px; color: var(--text-faint); font-size: 12px; }
.keyhints span { display: inline-flex; align-items: center; gap: 5px; }

/* --------------------------------------------------------------- summary */
.score-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(140px, 1fr)); gap: 12px; }
.score {
  background: var(--bg-elev); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 16px;
}
.score .num { font-size: 30px; font-weight: 700; letter-spacing: -0.03em; }
.score .lbl { font-size: 12px; color: var(--text-dim); text-transform: uppercase; letter-spacing: 0.07em; }
.score.ok .num { color: var(--good); }
.score.no .num { color: var(--bad); }

.review-list { display: grid; gap: 8px; }
.review-item {
  border: 1px solid var(--border); border-left: 3px solid var(--bad);
  border-radius: var(--radius-sm); background: var(--bg-elev); padding: 12px 14px;
}
.review-item.ok { border-left-color: var(--good); }
.review-item .q { font-weight: 550; }
.review-item .a { color: var(--text-dim); font-size: 14px; margin-top: 6px; white-space: pre-wrap; }

/* ----------------------------------------------------------------- stats */
.stat-rows { display: grid; gap: 8px; }
.stat-row {
  display: grid; grid-template-columns: 1fr 130px 84px; gap: 12px; align-items: center;
  padding: 10px 13px; border: 1px solid var(--border);
  border-radius: var(--radius-sm); background: var(--bg-elev);
}
.stat-row .name { min-width: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.stat-row .pct { text-align: right; font-family: var(--mono); font-size: 13px; color: var(--text-dim); }
.days { display: flex; gap: 6px; align-items: flex-end; height: 90px; }
.days .day {
  flex: 1; max-width: 46px; display: flex; flex-direction: column;
  justify-content: flex-end; gap: 4px;
}
.days .day .stack.idle { background: var(--bg-elev-2); border-radius: 3px; }
.days .day .stack { border-radius: 4px 4px 0 0; overflow: hidden; display: flex; flex-direction: column-reverse; }
.days .day .ok { background: var(--good); }
.days .day .no { background: var(--bad); }
.days .lbl { font-size: 10px; color: var(--text-faint); text-align: center; }

/* ---------------------------------------------------------------- toasts */
.toasts { position: fixed; right: 16px; bottom: 16px; display: grid; gap: 8px; z-index: 50; }
.toast {
  background: var(--bg-elev); border: 1px solid var(--border-strong);
  border-left: 3px solid var(--accent); border-radius: var(--radius-sm);
  padding: 11px 15px; box-shadow: var(--shadow); max-width: 380px;
  animation: fade 0.2s ease;
}
.toast.error { border-left-color: var(--bad); }
.toast.success { border-left-color: var(--good); }

@media (max-width: 620px) {
  .app { padding: 0 12px 60px; }
  .topbar { flex-wrap: wrap; }
  .flashcard { padding: 20px; border-radius: 14px; }
  .stat-row { grid-template-columns: 1fr 70px; }
  .stat-row .bar { display: none; }
  .judge { flex-direction: column; }
}