:root {
  --bg: #f8fafc;
  --surface: #ffffff;
  --surface-2: #f1f5f9;
  --text: #0f172a;
  --muted: #64748b;
  --border: #e2e8f0;
  --primary: #2563eb;
  --primary-ink: #ffffff;
  --accent: #7c3aed;
  --good: #16a34a;
  --warn: #d97706;
  --bad: #dc2626;
  --shadow: 0 10px 30px rgba(15, 23, 42, 0.08);
  --radius: 16px;
}
:root[data-theme="dark"],
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0b1220;
    --surface: #121a2b;
    --surface-2: #1a2338;
    --text: #e5edff;
    --muted: #94a3b8;
    --border: #263148;
    --primary: #60a5fa;
    --primary-ink: #0b1220;
    --accent: #a78bfa;
    --shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
  }
}
:root[data-theme="dark"] {
  --bg: #0b1220;
  --surface: #121a2b;
  --surface-2: #1a2338;
  --text: #e5edff;
  --muted: #94a3b8;
  --border: #263148;
  --primary: #60a5fa;
  --primary-ink: #0b1220;
  --accent: #a78bfa;
  --shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Text", "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  padding: env(safe-area-inset-top) 0 env(safe-area-inset-bottom);
  overscroll-behavior-y: contain;
}

/* ---------- Top bar ---------- */
.topbar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 10px 16px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: sticky; top: 0; z-index: 10;
}
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; }
.logo {
  display: inline-flex; align-items: center; justify-content: center;
  width: 32px; height: 32px; border-radius: 10px;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  color: #fff; font-weight: 800;
}
.logo sup { font-size: 0.7em; margin-left: 1px; }
.top-actions { display: flex; align-items: center; gap: 6px; }
#deckSelect {
  max-width: 42vw; padding: 6px 10px; border-radius: 10px;
  border: 1px solid var(--border); background: var(--surface-2); color: var(--text);
  font-size: 14px;
}
.icon-btn {
  width: 36px; height: 36px; border-radius: 10px;
  border: 1px solid var(--border); background: var(--surface-2); color: var(--text);
  font-size: 18px; cursor: pointer;
}
.icon-btn:active { transform: scale(0.96); }

/* ---------- Tabs ---------- */
.tabs {
  display: flex; gap: 4px; padding: 8px 12px;
  background: var(--surface); border-bottom: 1px solid var(--border);
  position: sticky; top: 56px; z-index: 9;
  overflow-x: auto;
}
.tab {
  padding: 8px 14px; border-radius: 999px;
  border: 1px solid transparent; background: transparent; color: var(--muted);
  font-weight: 600; cursor: pointer; white-space: nowrap;
}
.tab.active {
  background: var(--surface-2); color: var(--text); border-color: var(--border);
}

/* ---------- Views ---------- */
main { padding: 16px; max-width: 720px; margin: 0 auto; }
.view { display: none; }
.view.active { display: block; }

/* ---------- Learn ---------- */
.learn-head {
  display: flex; justify-content: space-between; align-items: center; gap: 12px;
  margin-bottom: 12px; flex-wrap: wrap;
}
.progress-pill {
  padding: 6px 12px; border-radius: 999px; background: var(--surface-2);
  color: var(--muted); font-weight: 600; font-size: 14px;
}
.learn-mode { display: flex; gap: 10px; font-size: 14px; color: var(--muted); flex-wrap: wrap; }
.learn-mode label { display: flex; align-items: center; gap: 4px; }

.card-stage {
  perspective: 1200px;
  min-height: 320px;
  display: flex; align-items: center; justify-content: center;
  padding: 10px 0 20px;
}
.card {
  position: relative;
  width: 100%; max-width: 520px; aspect-ratio: 3 / 2;
  cursor: pointer;
  transform-style: preserve-3d;
  transition: transform 0.5s cubic-bezier(0.2, 0.8, 0.2, 1);
  outline: none;
}
.card.flipped { transform: rotateY(180deg); }
.face {
  position: absolute; inset: 0;
  border-radius: 20px;
  background: var(--surface);
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
  padding: 20px;
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  text-align: center;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
}
.face.back {
  transform: rotateY(180deg);
  background: linear-gradient(160deg, var(--surface), var(--surface-2));
}
.word { font-size: clamp(28px, 6vw, 44px); font-weight: 800; letter-spacing: -0.02em; }
.phonetic { color: var(--muted); margin-top: 6px; font-size: 16px; }
.audio-btn {
  margin-top: 12px; width: 44px; height: 44px; border-radius: 50%;
  border: 1px solid var(--border); background: var(--surface-2); color: var(--text);
  font-size: 18px; cursor: pointer;
}
.hint { position: absolute; bottom: 14px; font-size: 12px; color: var(--muted); }
.pos {
  display: inline-block; padding: 4px 10px; border-radius: 999px;
  background: color-mix(in oklab, var(--accent) 20%, transparent);
  color: var(--accent); font-weight: 700; font-size: 13px; letter-spacing: 0.02em;
}
.face.back {
  justify-content: flex-start;
  padding-top: 24px;
  overflow-y: auto;
}
.vi {
  font-size: clamp(22px, 5vw, 30px);
  font-weight: 700;
  color: var(--primary);
  max-width: 92%;
  line-height: 1.3;
  text-align: center;
}
.groups {
  width: 92%;
  margin-top: 14px;
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.group-row {
  display: flex;
  gap: 8px;
  align-items: baseline;
  font-size: 14px;
  line-height: 1.4;
}
.group-pos {
  flex: 0 0 auto;
  display: inline-block;
  padding: 1px 8px;
  border-radius: 999px;
  background: color-mix(in oklab, var(--accent) 20%, transparent);
  color: var(--accent);
  font-weight: 700;
  font-size: 12px;
  text-transform: lowercase;
}
.group-terms {
  flex: 1;
  color: var(--muted);
}
.face.back .phonetic { margin-top: 12px; }
.face.back .audio-btn { margin-top: 8px; margin-bottom: 4px; }
/* Thẻ cũ dùng cardPos — ẩn vì giờ POS gộp vào groups */
#cardPos { display: none; }
.example {
  margin-top: 12px; font-style: italic; color: var(--muted);
  font-size: 14px; max-width: 90%;
}

.rate-row {
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px;
  margin-top: 8px;
}
.rate {
  padding: 10px 6px; border-radius: 12px; border: 1px solid var(--border);
  background: var(--surface); color: var(--text); font-weight: 700; cursor: pointer;
  font-size: 14px; line-height: 1.2;
}
.rate span { display: block; font-weight: 500; font-size: 11px; color: var(--muted); margin-top: 4px; }
.rate-again { border-color: color-mix(in oklab, var(--bad) 50%, var(--border)); }
.rate-hard  { border-color: color-mix(in oklab, var(--warn) 50%, var(--border)); }
.rate-good  { border-color: color-mix(in oklab, var(--good) 50%, var(--border)); }
.rate-easy  { border-color: color-mix(in oklab, var(--primary) 50%, var(--border)); }
.rate:active { transform: translateY(1px); }

.empty { text-align: center; padding: 48px 20px; color: var(--muted); }

/* ---------- List ---------- */
.list-head {
  display: flex; gap: 10px; align-items: center;
  margin-bottom: 12px;
}
#searchInput {
  flex: 1; padding: 10px 12px; border-radius: 12px;
  border: 1px solid var(--border); background: var(--surface); color: var(--text);
  font-size: 15px;
}
.card-list { display: flex; flex-direction: column; gap: 10px; }
.list-item {
  background: var(--surface); border: 1px solid var(--border); border-radius: 14px;
  padding: 12px 14px;
  display: grid; grid-template-columns: 1fr auto; gap: 6px 12px;
  align-items: center;
}
.li-word { font-weight: 700; font-size: 17px; }
.li-pos {
  display: inline-block; padding: 1px 8px; border-radius: 999px;
  background: var(--surface-2); color: var(--muted); font-size: 12px; margin-left: 6px;
  font-weight: 600;
}
.li-def { grid-column: 1 / -1; color: var(--muted); font-size: 14px; }
.li-actions { display: flex; gap: 6px; }
.li-actions button {
  width: 34px; height: 34px; border-radius: 10px;
  border: 1px solid var(--border); background: var(--surface-2);
  color: var(--text); cursor: pointer; font-size: 15px;
}
.li-actions .del { color: var(--bad); }

/* ---------- Add form ---------- */
.add-form { display: flex; flex-direction: column; gap: 14px; }
.add-form label { display: flex; flex-direction: column; gap: 6px; font-weight: 600; }
.add-form input, .add-form textarea {
  padding: 11px 12px; border-radius: 12px;
  border: 1px solid var(--border); background: var(--surface); color: var(--text);
  font-size: 16px; font-family: inherit;
}
.add-form textarea { resize: vertical; }
.input-row { display: flex; gap: 8px; }
.input-row input { flex: 1; }
.status {
  padding: 10px 12px; border-radius: 10px;
  background: var(--surface-2); color: var(--muted); font-size: 14px;
}
.status.error { color: var(--bad); background: color-mix(in oklab, var(--bad) 10%, var(--surface-2)); }
.status.success { color: var(--good); background: color-mix(in oklab, var(--good) 10%, var(--surface-2)); }
.form-actions { display: flex; gap: 10px; }

/* ---------- Buttons ---------- */
.primary, .secondary, .ghost, .danger {
  padding: 11px 16px; border-radius: 12px; font-weight: 700; cursor: pointer;
  font-size: 15px; border: 1px solid transparent;
}
.primary { background: var(--primary); color: var(--primary-ink); }
.secondary { background: var(--surface-2); color: var(--text); border-color: var(--border); }
.ghost { background: transparent; color: var(--muted); }
.danger { background: color-mix(in oklab, var(--bad) 15%, var(--surface)); color: var(--bad); border-color: color-mix(in oklab, var(--bad) 40%, var(--border)); }
.file-btn { display: inline-flex; align-items: center; justify-content: center; cursor: pointer; }

/* ---------- Stats ---------- */
.stats-grid {
  display: grid; grid-template-columns: repeat(2, 1fr); gap: 10px; margin-bottom: 20px;
}
.stat {
  background: var(--surface); border: 1px solid var(--border); border-radius: 14px;
  padding: 16px; text-align: center;
}
.stat-num { font-size: 28px; font-weight: 800; letter-spacing: -0.02em; }
.stat-label { color: var(--muted); font-size: 13px; margin-top: 4px; }
.io-row { display: flex; flex-wrap: wrap; gap: 10px; }
.muted { color: var(--muted); }
.small { font-size: 13px; }

/* ---------- Sheet ---------- */
.sheet {
  position: fixed; inset: 0; z-index: 50;
  background: rgba(0, 0, 0, 0.4);
  display: flex; align-items: flex-end; justify-content: center;
  padding: 0;
}
.sheet[hidden] { display: none; }
.sheet-body {
  width: 100%; max-width: 520px;
  background: var(--surface); border-top-left-radius: 20px; border-top-right-radius: 20px;
  padding: 20px 20px calc(20px + env(safe-area-inset-bottom));
  display: flex; flex-direction: column; gap: 10px;
}
.sheet-body h3 { margin: 0 0 8px; }
.row-btn {
  padding: 14px; border-radius: 12px; text-align: left; font-size: 15px; font-weight: 600;
  background: var(--surface-2); color: var(--text); border: 1px solid var(--border); cursor: pointer;
}
.row-btn.danger { color: var(--bad); border-color: color-mix(in oklab, var(--bad) 40%, var(--border)); background: color-mix(in oklab, var(--bad) 10%, var(--surface-2)); }
.row-btn.ghost { background: transparent; border-color: transparent; color: var(--muted); text-align: center; }