:root{
  --bg:#F8F8F5;--card:#FFFFFF;--ink:#10151C;--mute:#4A5260;--line:#DCDCD4;
  --jade:#1B3A6B;--jade-ink:#FFFFFF;--jade-soft:#D3DFEF;--seal:#B3261E;--seal-ink:#FFFFFF;
  color-scheme:light;
}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]){
  --bg:#0E141C;--card:#161E29;--ink:#E8EDF3;--mute:#9AA8BA;--line:#2B394A;
  --jade:#7FA6E8;--jade-ink:#0A1730;--jade-soft:#1D3050;--seal:#E0584F;--seal-ink:#1A0806;color-scheme:dark}}
:root[data-theme="dark"]{
  --bg:#0E141C;--card:#161E29;--ink:#E8EDF3;--mute:#9AA8BA;--line:#2B394A;
  --jade:#7FA6E8;--jade-ink:#0A1730;--jade-soft:#1D3050;--seal:#E0584F;--seal-ink:#1A0806;color-scheme:dark}

*{box-sizing:border-box}
html{scroll-behavior:smooth}
/* Chữ Việt dùng Be Vietnam Pro; chữ Hán và dấu thanh pinyin tự rơi về bộ chữ Trung rõ nét. */
:root{--font-zh:"Noto Sans SC","PingFang SC","Hiragino Sans GB","Microsoft YaHei",system-ui,sans-serif}
body{margin:0;background:var(--bg);color:var(--ink);font-family:"Be Vietnam Pro","Noto Sans SC","PingFang SC","Microsoft YaHei",system-ui,-apple-system,"Segoe UI",sans-serif;line-height:1.6;-webkit-font-smoothing:antialiased;text-rendering:optimizeLegibility}
.zh,[lang^="zh"]{font-family:var(--font-zh);line-height:1.6}
a{color:inherit}
a:focus-visible,button:focus-visible{outline:3px solid var(--jade);outline-offset:3px;border-radius:6px}

.top{max-width:1040px;margin:0 auto;padding:max(14px,env(safe-area-inset-top)) 20px 14px;display:flex;align-items:center;justify-content:space-between;gap:16px;flex-wrap:wrap}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none}
.seal{display:grid;place-items:center;width:38px;height:38px;border-radius:6px;background:var(--seal);color:var(--seal-ink);font-family:"Noto Serif SC","Songti SC",serif;font-weight:900;font-size:1.4rem;line-height:1}
.brand-name{font-weight:700;font-size:1.2rem}
.top nav{display:flex;gap:20px}
.top nav a{text-decoration:none;color:var(--mute);font-weight:600;font-size:.95rem}
.top nav a:hover{color:var(--jade)}

main{max-width:1040px;margin:0 auto;padding:0 20px}

.hero{display:grid;grid-template-columns:1.3fr 1fr;gap:32px;align-items:center;padding:40px 0 48px}
.hero h1{font-size:clamp(1.9rem,5vw,3rem);line-height:1.15;margin:0 0 14px}
.hero p{font-size:1.1rem;color:var(--mute);margin:0 0 24px;max-width:46ch}
.cta{display:flex;gap:12px;flex-wrap:wrap}
.btn{display:inline-block;font:inherit;font-weight:600;text-decoration:none;padding:13px 20px;border:1.5px solid var(--jade);border-radius:10px;color:var(--jade);background:transparent}
.btn.primary{background:var(--jade);color:var(--jade-ink)}
.btn:hover{filter:brightness(1.08)}

.block{padding:32px 0}
.block h2{font-size:1.5rem;margin:0 0 6px}
.lead{color:var(--mute);margin:0 0 20px}

.levels{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:repeat(4,1fr);gap:10px}
.levels li{display:flex}
.level{flex:1;display:flex;flex-direction:column;gap:4px;padding:10px 12px;border:1.5px solid var(--line);border-radius:14px;background:var(--card);text-decoration:none}
.level .lhead{display:flex;align-items:baseline;gap:8px;flex-wrap:wrap}
.level .lv{font-weight:700;font-size:1.05rem}
.level .zh{font-family:var(--font-zh);font-weight:500;color:var(--jade);font-size:.9rem}
.level .words{color:var(--mute);font-size:.74rem;line-height:1.35}
.level .state{margin-left:auto;font-size:.8rem;font-weight:600;color:var(--mute)}
a.level:hover{border-color:var(--jade)}
a.level .state{color:var(--jade)}
.level.soon{opacity:.75}

.tools{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:repeat(2,1fr);gap:12px}
.tool{display:flex;align-items:flex-start;gap:14px;padding:16px;border:1.5px solid var(--line);border-radius:12px;background:var(--card)}
.tool .ic{flex:none;display:grid;place-items:center;width:42px;height:42px;border-radius:8px;background:var(--jade-soft);color:var(--jade);font-family:"Noto Serif SC","Songti SC",serif;font-weight:900;font-size:1.3rem}
.tool h3{margin:0 0 2px;font-size:1.05rem}
.tool p{margin:0;color:var(--mute);font-size:.92rem}
.tool .state{display:inline-block;margin-top:6px;font-size:.85rem;font-weight:600;color:var(--mute)}
a.tool{text-decoration:none;color:inherit}
a.tool:hover{border-color:var(--jade)}
a.tool .state{color:var(--jade)}

.foot{max-width:1040px;margin:24px auto 0;padding:24px 20px max(32px,env(safe-area-inset-bottom));border-top:1px solid var(--line);color:var(--mute);font-size:.9rem}
.foot p{margin:0}

@media (max-width:760px){
  .hero{grid-template-columns:1fr;padding-top:20px}
  .levels{grid-template-columns:repeat(2,1fr)}
  .tools{grid-template-columns:1fr}
}
@media (max-width:420px){
  .level .state{display:none}
}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}}

.chip.ser{font-weight:700}
.chipsep{color:var(--line);align-self:center;padding:0 2px}
.chip.soon,.chip:disabled{opacity:.55;cursor:default}
.books{display:flex;flex-wrap:wrap;gap:8px;margin:0 0 22px}
.books .chip{font:inherit;font-size:1rem;font-weight:700;padding:9px 20px;border:1.5px solid var(--line);border-radius:24px;background:var(--card);color:var(--ink);cursor:pointer}
.books .chip[aria-pressed="true"]{background:var(--jade);border-color:var(--jade);color:var(--jade-ink)}
.books .chip:disabled{font-weight:600}
.hide{display:none!important}

/* Bố cục trang chủ: màn hình rộng có hai cột bên, màn hình nhỏ xếp các thẻ xuống dưới nội dung chính. */
.page{display:flex;flex-direction:column}
.page main{order:1}
.side{order:2;width:100%;max-width:1040px;margin:0 auto;padding:0 20px;display:grid;gap:14px;grid-template-columns:repeat(auto-fit,minmax(260px,1fr));align-content:start}
.card{padding:16px;border:1.5px solid var(--line);border-radius:14px;background:var(--card)}
.card h2{font-size:1.02rem;margin:0 0 10px}
.card .muted{color:var(--mute);font-size:.9rem;margin:0}
.card .btnrow{display:flex;gap:8px;flex-wrap:wrap;margin-top:10px}
.card .mini{display:inline-block;font:inherit;font-size:.9rem;font-weight:600;padding:7px 14px;border:1.5px solid var(--jade);border-radius:20px;background:var(--jade);color:var(--jade-ink);text-decoration:none;cursor:pointer}
.card .mini.alt{background:var(--card);color:var(--jade)}
.resume-t{font-weight:700;font-size:1.05rem;margin:0}
.prow{margin:0 0 10px}
.prow .pl{display:flex;justify-content:space-between;gap:8px;font-size:.88rem}
.prow .pl b{font-weight:700}
.pbar{height:6px;background:var(--line);border-radius:3px;overflow:hidden;margin-top:4px}
.pbar i{display:block;height:100%;background:var(--jade)}
@media (min-width:1480px){
  .page{display:grid;grid-template-columns:minmax(200px,1fr) 1040px minmax(200px,1fr);align-items:start}
  .page main{order:0;grid-column:2;grid-row:1}
  #sideL{order:0;grid-column:1;grid-row:1;grid-template-columns:1fr;max-width:300px;justify-self:end;margin:0 16px 0 0;padding:96px 0 0;position:sticky;top:12px}
}
.bookrow{flex-basis:100%;display:flex;align-items:center;gap:10px;margin:0 0 2px;font-weight:600;color:var(--mute);font-size:.92rem}
.booksel{font:inherit;font-size:.95rem;font-weight:700;padding:7px 34px 7px 14px;border:1.5px solid var(--jade);border-radius:20px;background:var(--card);color:var(--ink);cursor:pointer}
.levels.two{grid-template-columns:repeat(2,1fr)}
.tools.one{grid-template-columns:1fr}
.pcont{margin:4px 0 0;font-size:.86rem;color:var(--mute)}
.pcont .zh{font-family:var(--font-zh);font-weight:700;color:var(--ink)}
.plink{color:var(--jade);font-weight:700;text-decoration:none;margin-left:4px}
.plink:hover{text-decoration:underline}

/* ---------- Bổ sung giao diện (2026-11) ---------- */
.skip{position:absolute;left:-9999px;top:8px;z-index:20;background:var(--jade);color:var(--jade-ink);padding:8px 14px;border-radius:8px;font-weight:600;text-decoration:none}
.skip:focus{left:12px}
.sr{position:absolute!important;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}
button:focus-visible,a:focus-visible,[role="tab"]:focus-visible,[role="tabpanel"]:focus-visible,textarea:focus-visible{outline:3px solid var(--jade);outline-offset:3px}

/* Thẻ lật ở đầu trang */
.flash{display:flex;flex-direction:column;align-items:center;gap:10px;justify-self:center;width:100%;max-width:340px}
.fcard{position:relative;display:block;width:100%;aspect-ratio:1/1;padding:0;border:0;background:none;cursor:pointer;perspective:1200px;font:inherit;color:inherit}
.fcard .face{position:absolute;inset:0;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:4px;padding:18px;border:1.5px solid var(--line);border-radius:18px;background:var(--card);backface-visibility:hidden;-webkit-backface-visibility:hidden;transition:transform .5s cubic-bezier(.2,.7,.2,1);box-shadow:0 1px 0 var(--line)}
.fcard .front{background-image:linear-gradient(var(--line) 1px,transparent 1px),linear-gradient(90deg,var(--line) 1px,transparent 1px);background-size:50% 50%;background-position:center}
.fcard .back{transform:rotateY(180deg);text-align:center;align-items:stretch;justify-content:center}
.fcard.flipped .front{transform:rotateY(-180deg)}
.fcard.flipped .back{transform:rotateY(0)}
.fcard:hover .face{border-color:var(--jade)}
.fcard .big{font-weight:700;font-size:min(8.5rem,32vw);line-height:1.05;color:var(--ink)}
.fcard .read{font-size:1.35rem;font-weight:600;color:var(--jade);background:var(--card);padding:0 10px}
.fcard .mean{color:var(--mute);background:var(--card);padding:0 10px}
.fcard .blabel{font-size:.75rem;font-weight:700;letter-spacing:.06em;text-transform:uppercase;color:var(--mute);margin-top:6px}
.fcard .bzh{font-size:1.6rem;font-weight:500}
.fcard .bpy{color:var(--jade);font-weight:600}
.fcard .bvi{color:var(--mute);font-size:.95rem}
.fcard .bparts{display:flex;flex-wrap:wrap;justify-content:center;align-items:center;gap:6px 10px;font-size:.92rem}
.fcard .part{display:inline-flex;align-items:baseline;gap:5px}
.fcard .part b{font-size:1.5rem;font-weight:700}
.fcard .plus{color:var(--mute)}
.fctl{display:flex;gap:8px}
.ibtn{font:inherit;font-weight:600;font-size:.92rem;display:inline-flex;align-items:center;gap:6px;padding:7px 14px;border:1.5px solid var(--jade);border-radius:20px;background:var(--card);color:var(--jade);cursor:pointer}
.ibtn:hover{background:var(--jade-soft)}
.ibtn[aria-busy="true"]{opacity:.7}
.fhint{margin:0;font-size:.82rem;color:var(--mute);text-align:center}
@media (prefers-reduced-motion:reduce){.fcard .face{transition:none}}

/* Tabs giáo trình */
.tabs{display:flex;gap:6px;border-bottom:1.5px solid var(--line);margin:12px 0 16px}
.tab{font:inherit;font-weight:700;font-size:1rem;padding:9px 20px;margin-bottom:-1.5px;border:1.5px solid transparent;border-bottom:3px solid transparent;border-radius:10px 10px 0 0;background:none;color:var(--mute);cursor:pointer}
.tab:hover{color:var(--jade)}
.tab[aria-selected="true"]{color:var(--jade);border-bottom-color:var(--jade);background:var(--card);border-color:var(--line) var(--line) var(--jade)}
.tabpanel[hidden]{display:none}
.tabpanel:focus{outline:none}
.tabpanel .lead{margin-bottom:14px}

/* Chân trang */
.foot-links{display:flex;flex-wrap:wrap;gap:8px 20px;margin:0 0 10px}
.foot-links a,.linkbtn{font:inherit;font-size:.92rem;font-weight:600;color:var(--jade);background:none;border:0;padding:0;cursor:pointer;text-decoration:none}
.foot-links a:hover,.linkbtn:hover{text-decoration:underline}

/* Hộp sao lưu */
.bk{width:min(560px,calc(100vw - 32px));max-height:calc(100vh - 32px);border:1.5px solid var(--line);border-radius:16px;padding:18px 20px;background:var(--card);color:var(--ink)}
.bk::backdrop{background:rgba(10,15,25,.45)}
.bk-head{display:flex;align-items:center;justify-content:space-between;gap:12px}
.bk h2{font-size:1.15rem;margin:0}
.bk h3{font-size:1rem;margin:16px 0 4px}
.bk .muted{color:var(--mute);font-size:.9rem;margin:4px 0 8px}
.bk textarea{width:100%;font:13px/1.4 ui-monospace,Menlo,Consolas,monospace;padding:8px 10px;border:1.5px solid var(--line);border-radius:8px;background:var(--bg);color:var(--ink);resize:vertical;word-break:break-all}
.bk .btnrow{display:flex;flex-wrap:wrap;align-items:center;gap:8px;margin-top:8px}
.bk .mini{display:inline-block;font:inherit;font-size:.9rem;font-weight:600;padding:7px 14px;border:1.5px solid var(--jade);border-radius:20px;background:var(--jade);color:var(--jade-ink);cursor:pointer}
.bk .mini.alt{background:var(--card);color:var(--jade)}
.filebtn{position:relative;overflow:hidden}
.filebtn input{position:absolute;inset:0;opacity:0;cursor:pointer}
.bk-msg{font-size:.9rem;font-weight:600;margin:6px 0 0;color:var(--mute)}
.bk-msg.good{color:#1E7A3C}
.bk-msg.bad{color:#B3261E}
.card .btnrow button.mini{font:inherit;font-size:.85rem;font-weight:600}

/* Thanh tiến độ gọn: chỉ trên màn hình nhỏ */
.strip{display:none}
@media (max-width:767px){
  .strip{display:block;position:sticky;top:0;z-index:10;background:var(--bg);border-bottom:1px solid var(--line)}
  .strip-in{display:flex;align-items:center;gap:10px;padding:8px 16px}
  .strip-go{flex:1;min-width:0;display:flex;flex-direction:column;text-decoration:none;line-height:1.3}
  .strip-k{font-size:.72rem;font-weight:700;color:var(--mute);text-transform:uppercase;letter-spacing:.05em}
  .strip-v{font-weight:700;color:var(--jade);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
  .strip-n{font-size:.8rem;color:var(--mute);white-space:nowrap}
  .strip-b{font:inherit;font-size:.82rem;font-weight:600;padding:6px 12px;border:1.5px solid var(--jade);border-radius:18px;background:var(--card);color:var(--jade);cursor:pointer;white-space:nowrap}
  #sideL{display:none}
  .top{padding-left:16px;padding-right:16px}
  .top nav{gap:14px}
  main{padding:0 16px}
  .flash{max-width:260px}
}

/* ---------- Đầu trang gọn (2026-11-14) ---------- */
.hero{grid-template-columns:1fr 260px;gap:28px;padding:20px 0 12px}
.hero h1{font-size:clamp(1.6rem,4vw,2.4rem);line-height:1.2;margin:0 0 18px;max-width:18ch}
.flash{max-width:260px;gap:8px}
.fcard .big{font-size:6.5rem}
.fcard .read{font-size:1.15rem}
.fcard .bzh{font-size:1.3rem}
.fcard .bpy{font-size:.92rem}
.fcard .bvi{font-size:.85rem}
.fcard .bparts{font-size:.85rem}
.fcard .part b{font-size:1.25rem}
@media (max-width:767px){
  .hero{grid-template-columns:1fr 128px;gap:14px;align-items:center;padding:14px 0 6px}
  .hero h1{font-size:1.45rem;margin:0 0 12px}
  .hero .btn{padding:10px 16px;font-size:.95rem}
  .flash{max-width:128px;gap:6px}
  .fcard .face{padding:8px;border-radius:14px}
  .fcard .big{font-size:3.6rem}
  .fcard .read{font-size:.9rem;padding:0 6px}
  .fcard .mean{font-size:.75rem;padding:0 6px;line-height:1.3}
  .fcard .back .blabel,.fcard .back .bvi,.fcard .back .bparts{display:none}
  .fcard .bzh{font-size:.95rem;line-height:1.35}
  .fcard .bpy{font-size:.72rem;line-height:1.3}
  .fctl{gap:6px}
  .ibtn{padding:5px 10px;font-size:.85rem}
  .ibtn .lbl{display:none}
}

/* ---------- Thẻ công cụ gọn (2026-11-14) ---------- */
#tools .tools{grid-template-columns:repeat(4,1fr);gap:10px}
#tools .tool{align-items:center;gap:10px;padding:10px 12px;border-radius:12px;min-height:58px}
#tools .tool .ic{width:36px;height:36px;font-size:1.15rem}
.tool .tname{font-weight:700;font-size:.95rem;line-height:1.3}
a.tool:hover .tname{color:var(--jade)}
@media (max-width:900px){#tools .tools{grid-template-columns:repeat(3,1fr)}}
@media (max-width:600px){#tools .tools{grid-template-columns:repeat(2,1fr);gap:8px}#tools .tool{padding:9px 10px}.tool .tname{font-size:.9rem}}

/* Nhóm công cụ */
.tgroup{margin:0 0 16px}
.tgroup:last-child{margin-bottom:0}
.tgh{font-size:.8rem;font-weight:700;letter-spacing:.06em;text-transform:uppercase;color:var(--mute);margin:0 0 8px}

#vui-hoc{scroll-margin-top:70px}

/* ---------- Đầu trang: dòng phụ + số liệu (2026-11-14) ---------- */
.hero .eyebrow{display:inline-block;margin:0 0 10px;padding:4px 12px;border-radius:999px;background:var(--jade-soft);color:var(--jade);font-size:.82rem;font-weight:700;letter-spacing:.02em}
.hero h1{margin-bottom:10px}
.hero .sub{margin:0 0 16px;color:var(--mute);font-size:1.05rem;max-width:44ch;line-height:1.55}
.stats{list-style:none;margin:0 0 20px;padding:0;display:flex;flex-wrap:wrap;gap:8px}
.stats li{display:flex;align-items:baseline;gap:6px;padding:6px 12px;border:1.5px solid var(--line);border-radius:10px;background:var(--card);font-size:.88rem;color:var(--mute)}
.stats b{font-size:1.05rem;color:var(--ink)}
@media (max-width:767px){
  .hero{align-items:start}
  .hero .eyebrow{font-size:.72rem;padding:3px 10px;margin-bottom:6px}
  .hero .sub{font-size:.9rem;margin-bottom:10px}
  .stats{display:grid;grid-template-columns:1fr 1fr;gap:6px;margin-bottom:12px}
  .stats li{flex-direction:column;align-items:flex-start;gap:0;padding:5px 9px;font-size:.72rem;line-height:1.25}
  .stats li span{white-space:nowrap}
  .stats b{font-size:1rem}
}

/* ---------- Thẻ chữ theo cấp độ (2026-11-14) ---------- */
.hero .ftag{margin:0;font-size:.8rem;font-weight:700;color:var(--jade);text-align:center}
.hero .fnext{margin:0;font-size:.8rem;color:var(--mute);text-align:center}
.fnext a{color:var(--jade);font-weight:700;text-decoration:none}
.fnext a:hover{text-decoration:underline}
.fcard .big.mid{font-size:4.6rem}
.fcard .big.long{font-size:3.2rem;letter-spacing:-.02em}
.fcard .bwrap{display:flex;flex-direction:column;align-items:center;gap:2px}
.fcard .bwrap[hidden]{display:none}
.fcard .bmean{font-size:1rem;color:var(--ink)}
@media (max-width:767px){
  .hero .ftag{font-size:.68rem;line-height:1.25}
  .hero .fnext{font-size:.68rem;line-height:1.3}
  .fcard .big.mid{font-size:2.6rem}
  .fcard .big.long{font-size:1.8rem}
  .fcard .back .bwrap .blabel,.fcard .back #fPartsWrap{display:none}
  .fcard .back #fInfoWrap .bvi{display:block;font-size:.8rem}
}