/* Tiếng Việt — Daily Flashcards. Mobile-first, dark-mode default. */
:root {
  color-scheme: dark;
  --bg: #0f1420;
  --surface: #1a2130;
  --surface2: #232c40;
  --text: #e8ecf4;
  --muted: #8b95a8;
  --accent: #e8443a;      /* Vietnam red */
  --accent2: #ffd54a;     /* star yellow */
  --good: #4ade80;
  --bad: #f87171;
  --radius: 16px;
}
body.light {
  color-scheme: light;
  --bg: #f5f2ec;
  --surface: #ffffff;
  --surface2: #ece7dd;
  --text: #1c2230;
  --muted: #6b7280;
}
* { box-sizing: border-box; margin: 0; padding: 0; -webkit-tap-highlight-color: transparent; }
html, body { height: 100%; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: var(--bg); color: var(--text);
  transition: background .25s, color .25s;
}
#app { max-width: 520px; margin: 0 auto; padding: 16px 16px calc(24px + env(safe-area-inset-bottom)); min-height: 100vh; display: flex; flex-direction: column; }

.view { display: none; flex-direction: column; gap: 16px; flex: 1; }
.view.active { display: flex; }

.topbar { display: flex; align-items: center; justify-content: space-between; padding-top: 8px; }
.topbar h1 { font-size: 1.35rem; }
.icon-btn {
  background: var(--surface); border: none; color: var(--text);
  font-size: 1.15rem; width: 44px; height: 44px; border-radius: 12px; cursor: pointer;
}

.hero-stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; }
.stat-card {
  background: var(--surface); border-radius: var(--radius);
  padding: 18px 8px; text-align: center; display: flex; flex-direction: column; gap: 6px;
}
.stat-num { font-size: 2rem; font-weight: 700; color: var(--accent2); }
.stat-label { font-size: .78rem; color: var(--muted); }

.btn-primary {
  background: var(--accent); color: #fff; border: none;
  font-size: 1.15rem; font-weight: 700; padding: 20px;
  border-radius: var(--radius); cursor: pointer; min-height: 64px;
  transition: transform .08s, filter .15s;
}
.btn-primary:active { transform: scale(.97); }
.btn-primary:disabled { filter: grayscale(.6); opacity: .6; }
.btn-secondary {
  background: var(--surface); color: var(--text); border: none;
  font-size: 1.05rem; font-weight: 600; padding: 16px;
  border-radius: var(--radius); cursor: pointer; min-height: 56px;
}
.sync-status { text-align: center; font-size: .8rem; color: var(--muted); min-height: 1.2em; }

/* Quiz */
.quiz-top { display: flex; align-items: center; gap: 12px; padding-top: 8px; }
.quiz-progress { flex: 1; height: 8px; background: var(--surface2); border-radius: 4px; overflow: hidden; }
#quiz-bar { height: 100%; width: 0%; background: var(--accent); border-radius: 4px; transition: width .3s; }
.quiz-count { font-size: .85rem; color: var(--muted); min-width: 44px; text-align: right; }
.quiz-prompt { text-align: center; padding: 28px 8px 8px; }
.quiz-direction { font-size: .8rem; letter-spacing: .08em; text-transform: uppercase; color: var(--muted); margin-bottom: 14px; }
.quiz-front { font-size: 2rem; font-weight: 700; line-height: 1.25; overflow-wrap: break-word; white-space: pre-line; }
.quiz-deck { font-size: .75rem; color: var(--muted); margin-top: 12px; }
.choices { display: flex; flex-direction: column; gap: 12px; margin-top: 12px; }
.choice-btn {
  background: var(--surface); color: var(--text); border: 2px solid transparent;
  font-size: 1.2rem; padding: 18px 14px; min-height: 60px;
  border-radius: var(--radius); cursor: pointer; transition: border-color .15s, background .15s, transform .08s;
  line-height: 1.3; overflow-wrap: break-word;
}
.choice-btn:active { transform: scale(.98); }
.choice-btn.correct { border-color: var(--good); background: color-mix(in srgb, var(--good) 18%, var(--surface)); }
.choice-btn.wrong { border-color: var(--bad); background: color-mix(in srgb, var(--bad) 18%, var(--surface)); }
.choice-btn.dimmed { opacity: .45; }
.quiz-back { text-align: center; font-size: 1.9rem; font-weight: 700; color: var(--good); padding: 8px; overflow-wrap: break-word; white-space: pre-line; }
.reveal-row { display: flex; align-items: center; justify-content: center; gap: 10px; }
.reveal-row .quiz-back { flex: 1; }
.speak-btn { width: 52px; height: 52px; font-size: 1.4rem; flex: 0 0 auto; }
.speak-mini { background: var(--surface); border: none; color: var(--text); border-radius: 10px; width: 34px; height: 34px; margin-left: 8px; font-size: .95rem; cursor: pointer; vertical-align: middle; }
.selfgrade { display: flex; align-items: center; gap: 12px; margin-top: 6px; }
.selfgrade-label { font-size: .85rem; color: var(--muted); }
.btn-grade { flex: 1; min-height: 60px; font-size: 1.05rem; font-weight: 700; border: none; border-radius: var(--radius); cursor: pointer; }
.btn-grade.correct { background: color-mix(in srgb, var(--good) 25%, var(--surface)); color: var(--good); }
.btn-grade.wrong { background: color-mix(in srgb, var(--bad) 25%, var(--surface)); color: var(--bad); }
.feedback { text-align: center; min-height: 1.4em; font-size: .95rem; color: var(--muted); }
.hidden { display: none !important; }

/* Summary */
.summary-card {
  background: var(--surface); border-radius: var(--radius);
  padding: 32px 20px; text-align: center; display: flex; flex-direction: column; gap: 18px; margin-top: 10vh;
}
.summary-emoji { font-size: 3rem; }
.summary-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 10px; }
.sum-num { font-size: 1.5rem; font-weight: 700; color: var(--accent2); }
.sum-label { font-size: .78rem; color: var(--muted); }
.sum-streak { font-size: 1rem; color: var(--text); }

/* Progress */
.panel { background: var(--surface); border-radius: var(--radius); padding: 18px; display: flex; flex-direction: column; gap: 12px; }
.panel h3 { font-size: 1rem; color: var(--muted); font-weight: 600; }
.bar-wrap { display: flex; height: 18px; border-radius: 9px; overflow: hidden; background: var(--surface2); }
.bar.matured { background: var(--good); }
.bar.young { background: var(--accent2); }
.bar-legend { display: flex; gap: 14px; font-size: .78rem; color: var(--muted); flex-wrap: wrap; }
.bar-legend b { color: var(--text); }
.dot { display: inline-block; width: 10px; height: 10px; border-radius: 50%; margin-right: 5px; }
.dot.matured { background: var(--good); }
.dot.young { background: var(--accent2); }
.dot.new { background: var(--surface2); border: 1px solid var(--muted); }
.baseline-note { font-size: .8rem; color: var(--muted); line-height: 1.5; }
.week-chart { display: flex; align-items: flex-end; gap: 8px; height: 110px; }
.week-col { flex: 1; display: flex; flex-direction: column; align-items: center; gap: 6px; height: 100%; justify-content: flex-end; }
.week-bar { width: 100%; background: var(--accent); border-radius: 6px 6px 2px 2px; min-height: 3px; transition: height .3s; }
.week-bar.empty { background: var(--surface2); }
.week-label { font-size: .68rem; color: var(--muted); }
.week-val { font-size: .68rem; color: var(--text); }

@media (min-width: 700px) {
  #app { max-width: 640px; }
  .quiz-front { font-size: 2.6rem; }
  .choices { display: grid; grid-template-columns: 1fr 1fr; }
}