:root {
  --bg: #f4f6fb;
  --surface: #ffffff;
  --surface-2: #f0f3fa;
  --ink: #1c2331;
  --ink-soft: #5a6478;
  --primary: #c8472e;      /* đỏ son Trung Hoa */
  --primary-dark: #a83820;
  --accent: #2f6f8f;       /* xanh cho âm Hán-Việt */
  --accent-soft: #e3eff4;
  --gold: #d9a441;
  --good: #2e9e6b;
  --bad: #d8473f;
  --border: #e2e6ee;
  --shadow: 0 6px 20px rgba(28, 35, 49, 0.08);
  --radius: 16px;
  font-size: 16px;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--ink);
  line-height: 1.55;
  -webkit-tap-highlight-color: transparent;
  overflow-wrap: break-word;
}

/* Bỏ độ trễ chạm 300ms & cho mọi nút/ô bấm phản hồi nhanh trên thiết bị cảm ứng */
button, .tab, .lvl-btn, .quiz-opt, .gp-chip, .gp-mode, .hz-tile, .rad-tile, .flashcard, input, a {
  touch-action: manipulation;
}

/* Truy cập bằng bàn phím: viền focus rõ ràng (không hiện khi bấm chuột) */
:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 2px;
  border-radius: 6px;
}

/* ---------- Header ---------- */
.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
  padding: 16px 24px;
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  color: #fff;
}
.brand { display: flex; align-items: center; gap: 14px; }
.logo {
  font-size: 34px;
  width: 56px; height: 56px;
  display: grid; place-items: center;
  background: rgba(255,255,255,.15);
  border-radius: 14px;
  border: 1px solid rgba(255,255,255,.25);
}
.app-header h1 { margin: 0; font-size: 1.35rem; }
.tagline { margin: 0; font-size: .85rem; opacity: .9; }

.level-filter { display: flex; gap: 6px; background: rgba(255,255,255,.15); padding: 4px; border-radius: 12px; }
.lvl-btn {
  border: none; background: transparent; color: #fff;
  padding: 7px 14px; border-radius: 9px; cursor: pointer;
  font-size: .9rem; font-weight: 600; transition: .15s;
}
.lvl-btn.active { background: #fff; color: var(--primary-dark); }

/* ---------- Tabs ---------- */
.tabs {
  display: flex; gap: 4px; overflow-x: auto;
  padding: 10px 16px; background: var(--surface);
  border-bottom: 1px solid var(--border);
  position: sticky; top: 0; z-index: 10;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: none;          /* Firefox: ẩn thanh cuộn ngang */
}
.tabs::-webkit-scrollbar { display: none; }  /* WebKit: ẩn thanh cuộn */
.tab {
  border: none; background: transparent; color: var(--ink-soft);
  padding: 9px 16px; border-radius: 10px; cursor: pointer;
  font-size: .95rem; font-weight: 600; white-space: nowrap; transition: .15s;
}
.tab:hover { background: var(--surface-2); }
.tab.active { background: var(--accent-soft); color: var(--accent); }

/* ---------- Layout ---------- */
main {
  max-width: 880px; margin: 0 auto; padding: 24px 18px 60px;
}
.view-head { margin-bottom: 16px; }
.view-head h2 { margin: 0 0 4px; font-size: 1.3rem; }
.view-head p { margin: 0; color: var(--ink-soft); font-size: .92rem; }

/* ---------- Flashcard ---------- */
.fc-stage { display: flex; flex-direction: column; align-items: center; gap: 18px; }
.flashcard {
  width: 100%; max-width: 460px; min-height: 320px;
  background: var(--surface); border-radius: var(--radius);
  box-shadow: var(--shadow); border: 1px solid var(--border);
  padding: 28px; cursor: pointer; text-align: center;
  display: flex; flex-direction: column; justify-content: center; gap: 12px;
  transition: transform .12s;
}
.flashcard:active { transform: scale(.99); }
.fc-hanzi { font-size: 4.6rem; line-height: 1.1; font-weight: 500; }
.fc-pinyin { font-size: 1.5rem; color: var(--accent); font-weight: 600; }
.fc-hanviet {
  display: inline-block; font-size: 1.05rem; color: var(--accent);
  background: var(--accent-soft); padding: 3px 12px; border-radius: 20px;
  font-weight: 700; letter-spacing: .3px; margin: 0 auto;
}
.fc-meaning { font-size: 1.3rem; font-weight: 600; }
.fc-pos { font-size: .8rem; color: var(--ink-soft); }
.fc-example {
  margin-top: 8px; padding-top: 14px; border-top: 1px dashed var(--border);
  font-size: .98rem; color: var(--ink-soft);
}
.fc-example .ex-hz { font-size: 1.1rem; color: var(--ink); }
.fc-hint { font-size: .82rem; color: var(--ink-soft); font-style: italic; }
.hanviet-tip { font-size: .85rem; color: var(--accent); margin-top: 6px; }

.audio-btn {
  border: none; background: var(--accent-soft); color: var(--accent);
  width: 42px; height: 42px; border-radius: 50%; cursor: pointer;
  font-size: 1.1rem; display: inline-grid; place-items: center;
}
.audio-btn:hover { background: var(--accent); color: #fff; }

.fc-controls { display: flex; gap: 10px; flex-wrap: wrap; justify-content: center; }
.fc-progress { font-size: .9rem; color: var(--ink-soft); }

button.btn {
  border: none; border-radius: 12px; padding: 11px 20px;
  font-size: .95rem; font-weight: 600; cursor: pointer; transition: .15s;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); }
.btn-ghost { background: var(--surface-2); color: var(--ink); }
.btn-ghost:hover { background: #e6eaf3; }
.btn-good { background: var(--good); color: #fff; }
.btn-bad { background: var(--bad); color: #fff; }
.btn-gold { background: var(--gold); color: #fff; }

/* ---------- Review / SRS ---------- */
.srs-grades { display: flex; gap: 8px; flex-wrap: wrap; justify-content: center; }
.srs-stats { display: flex; gap: 18px; flex-wrap: wrap; justify-content: center; margin-bottom: 8px; }
.stat-pill {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: 12px; padding: 10px 16px; text-align: center; min-width: 90px;
}
.stat-pill .num { font-size: 1.4rem; font-weight: 700; }
.stat-pill .lbl { font-size: .78rem; color: var(--ink-soft); }

/* ---------- Quiz ---------- */
.quiz-card {
  background: var(--surface); border-radius: var(--radius);
  box-shadow: var(--shadow); border: 1px solid var(--border);
  padding: 26px; max-width: 560px; margin: 0 auto;
}
.quiz-q { font-size: 1.05rem; margin-bottom: 4px; color: var(--ink-soft); }
.quiz-prompt { font-size: 3rem; text-align: center; margin: 8px 0 20px; font-weight: 500; }
.quiz-prompt.small { font-size: 1.7rem; }
.quiz-options { display: grid; gap: 10px; }
.quiz-opt {
  border: 1.5px solid var(--border); background: var(--surface);
  border-radius: 12px; padding: 14px 16px; cursor: pointer;
  font-size: 1.05rem; text-align: left; transition: .12s;
}
.quiz-opt:hover { border-color: var(--accent); background: var(--accent-soft); }
.quiz-opt.correct { border-color: var(--good); background: #e7f6ee; color: #1c7a4f; }
.quiz-opt.wrong { border-color: var(--bad); background: #fbe9e7; color: #a8332a; }
.quiz-opt:disabled { cursor: default; }
.quiz-bar { display: flex; justify-content: space-between; align-items: center; margin-bottom: 14px; }
.quiz-score { font-weight: 700; }
.quiz-feedback { text-align: center; margin-top: 16px; font-weight: 600; min-height: 24px; }

/* ---------- Quiz: bật/tắt gợi ý ---------- */
.quiz-toggles { display: flex; gap: 18px; flex-wrap: wrap; justify-content: center; margin-bottom: 14px; }
.quiz-toggle { display: inline-flex; align-items: center; gap: 6px; font-size: .9rem; color: var(--ink-soft); cursor: pointer; user-select: none; }
.quiz-toggle input { width: 16px; height: 16px; accent-color: var(--accent); cursor: pointer; }
.quiz-hint { text-align: center; color: var(--accent); font-weight: 600; font-size: 1.25rem; margin-bottom: 14px; }

/* ---------- Tên người ---------- */
.names-section { margin-bottom: 26px; }
.names-title { margin: 0 0 4px; font-size: 1.08rem; }
.names-note { margin: 0 0 12px; color: var(--ink-soft); font-size: .9rem; }

/* ---------- Grammar ---------- */
.grammar-list { display: grid; gap: 14px; }
.grammar-item {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 18px 20px; box-shadow: var(--shadow);
}
.grammar-item .g-level {
  display: inline-block; font-size: .72rem; font-weight: 700;
  background: var(--accent-soft); color: var(--accent);
  padding: 2px 9px; border-radius: 10px; margin-bottom: 8px;
}
.grammar-item .g-level.hsk2 { background: #fbeede; color: var(--gold); }
.grammar-item h3 { margin: 0 0 8px; font-size: 1.12rem; }
.g-pattern {
  font-family: "SF Mono", ui-monospace, monospace; font-size: .95rem;
  background: var(--surface-2); padding: 8px 12px; border-radius: 8px;
  display: inline-block; margin-bottom: 10px; color: var(--primary-dark);
}
.g-note { margin: 0 0 12px; font-size: .95rem; }
.g-ex { display: grid; gap: 8px; }
.g-ex-row {
  border-left: 3px solid var(--accent); padding: 4px 0 4px 12px;
  display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap;
}
.g-ex-row .ex-hz { font-size: 1.1rem; }
.g-ex-row .ex-py { color: var(--accent); font-size: .9rem; }
.g-ex-row .ex-vn { color: var(--ink-soft); font-size: .92rem; }

/* ---------- Luyện ngữ pháp (điền từ / sắp xếp) ---------- */
.gp-modes { display: flex; gap: 6px; flex-wrap: wrap; margin-bottom: 16px; }
.gp-mode {
  border: 1.5px solid var(--border); background: var(--surface); color: var(--ink-soft);
  padding: 8px 14px; border-radius: 10px; cursor: pointer; font-weight: 600; font-size: .9rem; transition: .12s;
}
.gp-mode:hover { border-color: var(--accent); }
.gp-mode.active { background: var(--accent-soft); color: var(--accent); border-color: var(--accent); }
.gp-tag { font-size: .75rem; font-weight: 700; color: var(--primary); margin-bottom: 10px; text-transform: uppercase; letter-spacing: .3px; }
.gp-sentence { font-size: 1.8rem; text-align: center; margin: 8px 0 8px; line-height: 1.7; }
.gp-blank {
  display: inline-block; min-width: 2.4em; text-align: center;
  border-bottom: 3px solid var(--primary); color: var(--primary); font-weight: 700; margin: 0 4px;
}
.gp-hint { text-align: center; color: var(--ink-soft); font-size: .98rem; margin-bottom: 16px; }
.gp-answer {
  min-height: 56px; border: 2px dashed var(--border); border-radius: 12px; padding: 10px;
  display: flex; flex-wrap: wrap; gap: 8px; align-content: flex-start; margin-bottom: 12px; background: var(--surface-2);
}
.gp-answer-ph { color: var(--ink-soft); font-size: .9rem; font-style: italic; align-self: center; }
.gp-bank { display: flex; flex-wrap: wrap; gap: 8px; justify-content: center; margin-bottom: 14px; }
.gp-chip {
  border: 1.5px solid var(--border); background: var(--surface); border-radius: 10px;
  padding: 10px 14px; font-size: 1.25rem; cursor: pointer; transition: .12s;
}
.gp-chip:hover { border-color: var(--accent); background: var(--accent-soft); }
.gp-chip.placed { border-color: var(--accent); background: var(--accent-soft); color: var(--accent); }

/* ---------- Browse / search ---------- */
.search-bar { display: flex; gap: 10px; margin-bottom: 16px; flex-wrap: wrap; }
.search-bar input {
  flex: 1; min-width: 200px; padding: 12px 16px; font-size: 1rem;
  border: 1.5px solid var(--border); border-radius: 12px; background: var(--surface);
}
.search-bar input:focus { outline: none; border-color: var(--accent); }
.vocab-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(230px, 100%), 1fr)); gap: 12px; }
.vocab-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: 14px; padding: 14px 16px; box-shadow: var(--shadow);
}
.vocab-card .vc-top { display: flex; justify-content: space-between; align-items: flex-start; }
.vocab-card .vc-hz { font-size: 1.9rem; font-weight: 500; }
.vocab-card .vc-py { color: var(--accent); font-weight: 600; }
.vocab-card .vc-hv {
  font-size: .8rem; color: var(--accent); background: var(--accent-soft);
  padding: 1px 8px; border-radius: 10px; font-weight: 700; display: inline-block; margin: 4px 0;
}
.vocab-card .vc-vn { font-size: .98rem; }
.vocab-card .vc-lvl { font-size: .68rem; color: var(--ink-soft); text-transform: uppercase; }
.vocab-card .vc-ex { font-size: .82rem; color: var(--ink-soft); margin-top: 6px; }

/* ---------- Footer & misc ---------- */
.app-footer {
  display: flex; justify-content: space-between; align-items: center; gap: 12px;
  flex-wrap: wrap; max-width: 880px; margin: 0 auto; padding: 16px 18px 30px;
  color: var(--ink-soft); font-size: .85rem;
}
.link-btn { background: none; border: none; color: var(--primary); cursor: pointer; font-size: .85rem; text-decoration: underline; }
.empty { text-align: center; color: var(--ink-soft); padding: 50px 0; }
.empty .big { font-size: 3rem; margin-bottom: 10px; }
.progress-track { width: 100%; max-width: 460px; height: 8px; background: var(--surface-2); border-radius: 6px; overflow: hidden; }
.progress-track > div { height: 100%; background: var(--good); transition: width .3s; }

/* ---------- Chữ Hán bấm được ---------- */
.hz-click { cursor: pointer; border-radius: 6px; transition: background .12s, color .12s; padding: 0 1px; }
.hz-click:hover { background: var(--accent-soft); color: var(--accent); }

/* ---------- Tập viết: lưới chữ ---------- */
.hz-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(78px, 100%), 1fr)); gap: 10px; }
.hz-tile {
  background: var(--surface); border: 1px solid var(--border); border-radius: 12px;
  padding: 10px 6px; text-align: center; cursor: pointer; box-shadow: var(--shadow); transition: .12s;
}
.hz-tile:hover { border-color: var(--primary); transform: translateY(-2px); }
.hz-tile-char { font-size: 2rem; line-height: 1.1; }
.hz-tile-hv { font-size: .72rem; color: var(--accent); font-weight: 700; margin-top: 2px; }

/* ---------- Học bộ thủ: lưới ---------- */
.rad-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(140px, 100%), 1fr)); gap: 12px; }
.rad-tile {
  background: var(--surface); border: 1px solid var(--border); border-radius: 14px;
  padding: 14px 12px; text-align: center; cursor: pointer; box-shadow: var(--shadow); transition: .12s;
}
.rad-tile:hover { border-color: var(--primary); transform: translateY(-2px); }
.rad-tile-char { font-size: 2.4rem; line-height: 1.1; }
.rad-tile-hv { font-size: .9rem; color: var(--accent); font-weight: 700; margin-top: 2px; }
.rad-tile-ng { font-size: .76rem; color: var(--ink-soft); margin-top: 2px; min-height: 1.4em; }
.rad-tile-count { font-size: .7rem; color: var(--primary); margin-top: 6px; font-weight: 600; }

/* ---------- Bảng chi tiết chữ (modal) ---------- */
.hz-overlay {
  position: fixed; inset: 0; background: rgba(20,25,35,.55);
  display: none; align-items: flex-start; justify-content: center;
  padding: 30px 16px; z-index: 100; overflow-y: auto;
}
.hz-overlay.open { display: flex; }
.hz-panel {
  background: var(--surface); border-radius: 18px; box-shadow: 0 20px 60px rgba(0,0,0,.3);
  width: 100%; max-width: 560px; padding: 22px; position: relative; animation: hzPop .15s ease;
}
@keyframes hzPop { from { transform: scale(.96); opacity: .6; } to { transform: scale(1); opacity: 1; } }
.hz-close {
  position: absolute; top: 12px; right: 14px; border: none; background: var(--surface-2);
  width: 34px; height: 34px; border-radius: 50%; font-size: 1.4rem; line-height: 1; cursor: pointer; color: var(--ink-soft);
}
.hz-close:hover { background: #e6eaf3; }
.hz-top { display: flex; gap: 20px; flex-wrap: wrap; align-items: center; }
.hz-writer-wrap { text-align: center; }
.hz-writer {
  width: 220px; height: 220px; max-width: 100%; margin: 0 auto; border: 2px dashed var(--border);
  border-radius: 12px; background:
    linear-gradient(var(--border),var(--border)) center/100% 1px no-repeat,
    linear-gradient(var(--border),var(--border)) center/1px 100% no-repeat,
    var(--surface);
  display: grid; place-items: center;
}
.hz-nostroke { font-size: 6rem; }
.hz-writer-controls { display: flex; gap: 8px; justify-content: center; margin-top: 12px; flex-wrap: wrap; }
.hz-writer-controls .btn { padding: 8px 14px; font-size: .85rem; }
.hz-quiz-msg { min-height: 20px; margin-top: 8px; font-size: .85rem; color: var(--ink-soft); }
.hz-meta { flex: 1; min-width: 160px; }
.hz-char { font-size: 3.4rem; line-height: 1; margin-bottom: 8px; }
.hz-py { font-size: 1.35rem; color: var(--accent); font-weight: 600; margin-bottom: 4px; }
.hz-vn { font-size: 1.15rem; font-weight: 600; margin-top: 6px; }
.hz-radtag { font-size: .7rem; font-weight: 700; letter-spacing: 1px; color: var(--primary); }

/* hàng bộ thủ bấm được trong chi tiết chữ */
.hz-radrow.hz-clickable { cursor: pointer; transition: .12s; }
.hz-radrow.hz-clickable:hover { background: var(--accent-soft); }
.hz-go { font-size: .76rem; font-weight: 600; color: var(--accent); }

/* lưới chữ ví dụ trong chi tiết bộ thủ */
.hz-exgrid { display: grid; grid-template-columns: repeat(auto-fill, minmax(64px, 1fr)); gap: 8px; }
.hz-extile { padding: 8px 4px; }
.hz-extile .hz-tile-char { font-size: 1.7rem; }

.hz-sections { margin-top: 18px; display: grid; gap: 12px; }
.hz-sec { background: var(--surface-2); border-radius: 12px; padding: 12px 14px; }
.hz-sec h4 { margin: 0 0 6px; font-size: .92rem; }
.hz-sec p { margin: 0; font-size: .95rem; }
.hz-sec.hz-tip { background: #fff8ec; border: 1px solid #f0e0c0; }
.hz-parts { display: flex; flex-wrap: wrap; gap: 8px; }
.hz-part { background: var(--surface); border: 1px solid var(--border); border-radius: 8px; padding: 4px 9px; font-size: .9rem; }
.hz-part b { font-size: 1.1rem; }
.hz-muted { color: var(--ink-soft); font-size: .9rem; }

/* ============ Đáp ứng đa thiết bị (responsive) ============ */

/* Thiết bị cảm ứng: bảo đảm vùng chạm đủ lớn (≥44px) cho mọi nút */
@media (pointer: coarse) {
  button.btn { min-height: 46px; }
  .quiz-opt { min-height: 50px; }
  .gp-chip { min-height: 46px; }
  .gp-mode, .lvl-btn, .tab { min-height: 42px; }
  .audio-btn { width: 46px; height: 46px; }
  .hz-close { width: 40px; height: 40px; }
  .hz-tile, .rad-tile { padding-top: 14px; padding-bottom: 14px; }
}

/* Máy tính bảng & màn hình vừa */
@media (max-width: 768px) {
  .app-header h1 { font-size: 1.22rem; }
  main { padding: 20px 16px 56px; }
  .quiz-prompt { font-size: 2.7rem; }
  .gp-sentence { font-size: 1.55rem; }
}

/* Điện thoại */
@media (max-width: 560px) {
  /* Header xếp dọc: thương hiệu trên, bộ lọc cấp độ trải rộng bên dưới */
  .app-header { padding: 12px 14px; gap: 10px; flex-direction: column; align-items: stretch; }
  .logo { width: 48px; height: 48px; font-size: 28px; }
  .app-header h1 { font-size: 1.15rem; }
  .level-filter { justify-content: stretch; }
  .level-filter .lvl-btn { flex: 1; text-align: center; }

  .tabs { padding: 8px 12px; }
  .tab { padding: 8px 13px; font-size: .9rem; }

  main { padding: 16px 12px 48px; }
  .view-head h2 { font-size: 1.15rem; }
  .view-head p { font-size: .88rem; }

  .flashcard { min-height: 260px; padding: 22px 18px; }
  .fc-hanzi { font-size: 3.4rem; }
  .fc-pinyin { font-size: 1.3rem; }
  .fc-meaning { font-size: 1.15rem; }
  /* 3 nút điều khiển chia đều một hàng cho gọn */
  .fc-controls { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; width: 100%; }
  .fc-controls .btn { padding: 12px 6px; }

  .quiz-card { padding: 18px 15px; }
  .quiz-prompt { font-size: 2.4rem; margin: 6px 0 16px; }
  .quiz-opt { padding: 13px 14px; font-size: 1rem; }
  .quiz-hint { font-size: 1.1rem; }
  .quiz-toggles { gap: 14px; }

  .srs-stats { gap: 10px; }
  .stat-pill { flex: 1; min-width: 68px; padding: 9px 10px; }

  .grammar-item { padding: 16px; }
  .gp-mode { flex: 1; text-align: center; padding: 9px 6px; }
  .gp-sentence { font-size: 1.4rem; line-height: 1.6; }
  .gp-chip { font-size: 1.15rem; padding: 11px 13px; }
  .gp-answer { min-height: 52px; }

  .hz-overlay { padding: 14px 10px; }
  .hz-panel { padding: 18px 15px; }
  .hz-top { gap: 14px; justify-content: center; }
  .hz-char { font-size: 3rem; }
}

/* Điện thoại nhỏ */
@media (max-width: 380px) {
  .fc-hanzi { font-size: 3rem; }
  .quiz-prompt { font-size: 2.1rem; }
  .gp-sentence { font-size: 1.25rem; }
  .tab { font-size: .85rem; padding: 7px 10px; }
}

/* Tôn trọng tùy chọn giảm chuyển động của hệ điều hành */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
    scroll-behavior: auto !important;
  }
}