/* Karteikasten – giao diện chung và trang học */
:root{
  --bg:#0F1729; --surface:#172036; --card:rgba(40,45,60,.95); --inner:#111a2e; --line:#1F2A3D; --card-line:rgba(255,255,255,.1);
  --ink:#F6F7F9; --muted:#B3BDCC; --faint:#8190A5;
  --primary:#F6F7F9; --on-primary:#0F1729;
  --accent:#6EE7B7;
  --b-learn-bg:#2B3B55; --b-learn:#85B2F9;
  --b-new-bg:rgba(245,158,11,.12); --b-new:#FDE68A;
  --b-done-bg:rgba(16,185,129,.12); --b-done:#A7F3D0; --b-done-line:rgba(16,185,129,.3);
  --b-bad-bg:rgba(239,68,68,.12); --b-bad:#FCA5A5;
  --der:#85B2F9; --die:#FCA5A5; --das:#6EE7B7; --none:#B3BDCC;
  --focus:#85B2F9;
  --ease:cubic-bezier(.2,.7,.2,1);
  --font:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;
  color-scheme:dark;
  box-sizing:border-box;
  padding-top:env(safe-area-inset-top,0px);
  padding-bottom:env(safe-area-inset-bottom,0px);
}
@media (prefers-color-scheme: light){
  :root:not([data-theme="dark"]){
    --bg:#F6F7F9; --surface:#FFFFFF; --card:#FFFFFF; --inner:#F1F4F8; --line:#E2E8F0; --card-line:#E2E8F0;
    --ink:#0F1729; --muted:#475569; --faint:#64748B;
    --primary:#0F1729; --on-primary:#F6F7F9; --accent:#047857;
    --b-learn-bg:#DBEAFE; --b-learn:#1D4ED8; --b-new-bg:#FEF3C7; --b-new:#92400E;
    --b-done-bg:#D1FAE5; --b-done:#065F46; --b-done-line:#A7F3D0; --b-bad-bg:#FEE2E2; --b-bad:#B91C1C;
    --der:#1D4ED8; --die:#B91C1C; --das:#047857; --none:#475569; --focus:#1D4ED8;
    color-scheme:light;
  }
}
:root[data-theme="light"]{
    --bg:#F6F7F9; --surface:#FFFFFF; --card:#FFFFFF; --inner:#F1F4F8; --line:#E2E8F0; --card-line:#E2E8F0;
    --ink:#0F1729; --muted:#475569; --faint:#64748B;
    --primary:#0F1729; --on-primary:#F6F7F9; --accent:#047857;
    --b-learn-bg:#DBEAFE; --b-learn:#1D4ED8; --b-new-bg:#FEF3C7; --b-new:#92400E;
    --b-done-bg:#D1FAE5; --b-done:#065F46; --b-done-line:#A7F3D0; --b-bad-bg:#FEE2E2; --b-bad:#B91C1C;
    --der:#1D4ED8; --die:#B91C1C; --das:#047857; --none:#475569; --focus:#1D4ED8;
    color-scheme:light;
}
*,*::before,*::after{box-sizing:inherit}
html{scroll-padding-top:env(safe-area-inset-top,0px)}
body{margin:0;background:var(--bg);color:var(--ink);font-family:var(--font);font-size:16px;line-height:1.55;-webkit-font-smoothing:antialiased}
button,select{font:inherit;color:inherit}
button{cursor:pointer}
:focus-visible{outline:2px solid var(--focus);outline-offset:3px;border-radius:8px}
.sr{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}
svg{width:18px;height:18px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round;stroke-linejoin:round;flex:none}

/* Header */
.topbar{border-bottom:1px solid var(--line)}
.top{max-width:1120px;margin:0 auto;padding:14px clamp(16px,4vw,32px);display:flex;flex-wrap:wrap;gap:14px 28px;align-items:flex-end;justify-content:space-between}
.brand{display:flex;gap:10px;align-items:center;align-self:center}
.mark{width:36px;height:36px;background:var(--primary);color:var(--on-primary);display:grid;place-items:center;font-weight:900;font-size:17px;border-radius:8px;letter-spacing:-.02em}
.brand h1{margin:0;font-size:1.05rem;line-height:1.2;font-weight:800}
.brand p{margin:0;color:var(--muted);font-size:.8rem}
.controls{display:flex;flex-wrap:wrap;gap:10px 16px;align-items:flex-end}
.field{display:flex;flex-direction:column;gap:4px}
.field>span{font-size:.75rem;color:var(--faint);font-weight:600}
select{min-height:44px;padding:0 36px 0 12px;border:1px solid var(--line);border-radius:8px;background:var(--surface);appearance:none;font-weight:500;
  background-image:linear-gradient(45deg,transparent 50%,var(--muted) 50%),linear-gradient(135deg,var(--muted) 50%,transparent 50%);
  background-position:calc(100% - 18px) 50%,calc(100% - 12px) 50%;background-size:6px 6px;background-repeat:no-repeat;max-width:100%}
.seg{display:inline-flex;gap:4px;padding:3px;border:1px solid var(--line);border-radius:10px;background:var(--surface)}
.seg button{min-height:38px;padding:0 12px;border:0;border-radius:7px;background:transparent;color:var(--muted);font-weight:600;font-size:.88rem;white-space:nowrap;transition:background-color .15s,color .15s}
.seg button:hover{color:var(--ink)}
.seg button[aria-pressed="true"]{background:var(--primary);color:var(--on-primary)}
.seg.is-off{opacity:.4}
.seg.is-off button{cursor:not-allowed}

/* Layout */
.layout{max-width:1120px;margin:0 auto;padding:32px clamp(16px,4vw,32px) 64px;display:grid;gap:32px}
@media (min-width:920px){.layout{grid-template-columns:minmax(0,1fr) 320px;gap:40px}}
.study{min-width:0;max-width:680px;width:100%;justify-self:center}

.chips{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:14px}
.chip{display:inline-flex;align-items:center;gap:6px;font-size:.78rem;font-weight:600;padding:4px 10px;border-radius:8px;background:var(--b-done-bg);color:var(--b-done);border:1px solid var(--b-done-line)}
.chip svg{width:13px;height:13px;stroke-width:2.6}
.chip.blue{background:var(--b-learn-bg);color:var(--b-learn);border-color:transparent}

.progress{display:flex;align-items:center;gap:12px;margin-bottom:16px;font-size:.82rem;color:var(--muted);font-variant-numeric:tabular-nums}
.bar{flex:1;height:6px;background:var(--line);border-radius:999px;overflow:hidden}
.bar i{display:block;height:100%;width:0;background:var(--accent);border-radius:999px;transition:width .3s var(--ease)}

/* Flashcard */
.stage{position:relative;perspective:1600px;--g:var(--none)}
.card{position:relative;display:grid;min-height:clamp(360px,54vh,460px);transform-style:preserve-3d;transition:transform .5s var(--ease);cursor:pointer}
.card.is-flipped{transform:rotateY(180deg)}
.card.no-anim{transition:none}
.card.deal{animation:deal .22s var(--ease)}
@keyframes deal{from{opacity:0;translate:0 12px}to{opacity:1;translate:0 0}}
.card.is-static{cursor:default}
.face{grid-area:1/1;background:color-mix(in srgb,var(--card) 88%,var(--g) 12%);border:2px solid color-mix(in srgb,var(--g) 58%,var(--card-line));border-radius:24px;backface-visibility:hidden;-webkit-backface-visibility:hidden;display:flex;flex-direction:column;padding:18px 20px 22px;overflow:hidden}
.back{transform:rotateY(180deg)}
.card-top{display:flex;align-items:center;gap:8px;padding-right:48px;min-height:28px}
.badge{display:inline-flex;align-items:center;font-size:.72rem;font-weight:600;padding:4px 9px;border-radius:10px;line-height:1.2;white-space:nowrap}
.b-learn{background:var(--b-learn-bg);color:var(--b-learn)}
.b-new{background:var(--b-new-bg);color:var(--b-new)}
.b-done{background:var(--b-done-bg);color:var(--b-done)}
.b-bad{background:var(--b-bad-bg);color:var(--b-bad)}
.counter{font-size:.75rem;font-weight:600;color:var(--muted);font-variant-numeric:tabular-nums;padding:4px 8px;border-radius:10px;background:var(--inner)}
.center{flex:1;display:flex;flex-direction:column;align-items:center;justify-content:center;text-align:center;padding:20px 8px}
.head{margin:0;font-size:clamp(2.25rem,7vw,3.5rem);line-height:1.08;font-weight:800;letter-spacing:-.02em;hyphens:auto;-webkit-hyphens:auto;overflow-wrap:anywhere}
.head.vi{font-size:clamp(1.75rem,5.5vw,2.6rem);font-weight:750;hyphens:none}
.sub{margin:10px 0 0;color:var(--muted);font-size:1rem}
.sub .art{color:var(--g);font-weight:700}
.q{margin:0 0 10px;font-size:.9rem;color:var(--muted);font-weight:500}
.hint{margin:0;text-align:center;font-size:.8rem;color:var(--faint)}
.t-key{display:none}
@media (hover:hover) and (pointer:fine){.t-key{display:inline}.t-touch{display:none}}

/* mặt sau chế độ đoán der/die/das nhiều nội dung hơn: dồn lên trên. Chế độ lật thẻ giữ ở giữa như mặt trước. */
.card.is-static .back .center{justify-content:flex-start;padding-top:24px}
.head .art{color:var(--g)}
.exbox + .hint{margin-top:10px}
.de{font-size:clamp(1.9rem,5.5vw,2.75rem);line-height:1.1;font-weight:800;letter-spacing:-.02em;hyphens:auto;-webkit-hyphens:auto;overflow-wrap:anywhere}
.de .art{color:var(--g)}
.mean{margin:8px 0 0;font-size:1.2rem;font-weight:600;color:var(--ink)}
.gram{margin:10px 0 0;font-size:.85rem;color:var(--muted)}
.exbox{margin-top:auto;background:var(--inner);border:1px solid var(--line);border-radius:14px;padding:12px 14px;text-align:left}
.exbox .lbl{display:flex;align-items:center;gap:6px;font-size:.75rem;font-weight:600;color:var(--muted);margin:0 0 6px}
.exbox .lbl svg{width:14px;height:14px}
.ex{margin:0;font-weight:600;font-size:1rem}
.exv{margin:2px 0 0;color:var(--muted);font-size:.92rem}
.ex-speak{display:inline-flex;align-items:center;gap:6px;min-height:32px;margin-top:8px;padding:0 10px;border:1px solid var(--line);background:transparent;border-radius:8px;font-size:.8rem;font-weight:600;color:var(--muted)}
.ex-speak:hover{color:var(--ink);border-color:var(--muted)}
.ex-speak svg{width:14px;height:14px}

.speak{position:absolute;z-index:2;top:12px;right:12px;width:44px;height:44px;display:grid;place-items:center;border:0;border-radius:12px;background:transparent;color:var(--muted);transition:background-color .15s,color .15s}
.speak:hover{color:var(--ink);background:var(--inner)}
.speak svg{width:20px;height:20px}
.speak[hidden]{display:none}

/* Summary / empty */
.panel{min-height:clamp(360px,54vh,460px);background:var(--card);border:2px solid var(--card-line);border-radius:24px;padding:32px 24px;display:flex;flex-direction:column;align-items:center;justify-content:center;text-align:center;gap:12px}
.panel h2{margin:0;font-size:clamp(1.75rem,5vw,2.4rem);font-weight:900;line-height:1.15;letter-spacing:-.02em}
.panel p{margin:0;max-width:44ch;color:var(--muted)}
.tally{display:grid;grid-template-columns:1fr 1fr;gap:10px;width:100%;max-width:380px;margin:6px 0}
.tally div{background:var(--surface);border:1px solid var(--line);border-radius:8px;padding:12px;text-align:left}
.tally b{display:block;font-size:1.5rem;line-height:1.1;font-weight:900;font-variant-numeric:tabular-nums}
.tally span{font-size:.85rem;color:var(--muted)}

/* Buttons */
.actions{display:flex;gap:10px;margin-top:20px;flex-wrap:wrap}
.actions{flex-wrap:nowrap}
.act-mid{flex:1 1 0;display:flex;gap:10px;min-width:0}
.act-mid .btn{min-width:0}
.progress .nav{flex:none;width:40px;height:40px;display:grid;place-items:center;padding:0;border:1px solid var(--line);border-radius:10px;background:var(--surface);color:var(--ink);transition:background-color .15s}
.progress .nav:hover{background:var(--inner)}
.progress .nav svg{width:20px;height:20px}
.progress .nav:disabled{opacity:.35;cursor:not-allowed}
.progress .nav:disabled:hover{background:var(--surface)}
@media (max-width:420px){.act-mid .btn{padding:0 8px;font-size:.92rem;white-space:nowrap}.act-mid .btn kbd,.act-mid .btn svg{display:none}}
/* chỉ mặt đang hiện nhận cú bấm (Safari/cảm ứng có thể bắt nhầm mặt đã úp) */
.card:not(.is-flipped) .back,.card.is-flipped .front{pointer-events:none}
.btn{flex:1 1 0;min-width:110px;min-height:48px;padding:0 18px;border:1px solid var(--line);border-radius:8px;background:transparent;font-weight:600;font-size:1rem;display:inline-flex;align-items:center;justify-content:center;gap:8px;transition:background-color .15s,opacity .15s,transform .1s}
.btn:hover{background:var(--surface)}
.btn:active{transform:translateY(1px)}
.btn.primary{background:var(--primary);color:var(--on-primary);border-color:var(--primary)}
.btn.primary:hover{opacity:.9}
.btn.g{color:var(--c);font-weight:700;font-size:1.1rem;border-color:color-mix(in srgb,var(--c) 35%,transparent);background:color-mix(in srgb,var(--c) 8%,transparent)}
.btn.g:hover{background:color-mix(in srgb,var(--c) 16%,transparent)}
.btn.panel-btn{flex:0 0 auto;margin-top:6px;min-width:220px}
.btn kbd{font:inherit;font-size:.7rem;font-weight:600;opacity:.6;border:1px solid currentColor;border-radius:5px;padding:0 5px;line-height:1.5}
@media not ((hover:hover) and (pointer:fine)){.btn kbd{display:none}}
.keys{margin:12px 0 0;font-size:.8rem;color:var(--faint);text-align:center;display:none}
@media (hover:hover) and (pointer:fine){.keys{display:block}}

/* Leitner panel */
.kasten{align-self:start;background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:20px}
.eyebrow{margin:0 0 4px;font-size:.75rem;font-weight:600;letter-spacing:.12em;text-transform:uppercase;color:var(--accent)}
.kasten h2{margin:0 0 6px;font-size:1.25rem;font-weight:900;letter-spacing:-.01em}
.kasten>p{margin:0 0 16px;color:var(--muted);font-size:.88rem}
.boxes{list-style:none;margin:0;padding:0;display:grid;gap:8px}
.boxes li{display:grid;grid-template-columns:1fr auto;gap:8px 10px;align-items:center;background:var(--inner);border:1px solid var(--line);border-radius:8px;padding:10px 12px}
.boxes .n{font-weight:700;font-size:.95rem}
.boxes .d{display:block;color:var(--muted);font-size:.78rem;font-weight:400}
.boxes .c{font-variant-numeric:tabular-nums;font-weight:600;font-size:.75rem;padding:3px 9px;border-radius:8px;background:var(--b-learn-bg);color:var(--b-learn)}
.boxes li:first-child .c{background:var(--b-new-bg);color:var(--b-new)}
.boxes li:last-child .c{background:var(--b-done-bg);color:var(--b-done)}
.boxes .t{grid-column:1/-1;height:4px;border-radius:999px;background:var(--line);overflow:hidden}
.boxes .t i{display:block;height:100%;background:var(--b-learn);border-radius:999px;transition:width .3s var(--ease)}
.boxes li:first-child .t i{background:var(--b-new)}
.boxes li:last-child .t i{background:var(--accent)}
.legend{margin:18px 0 0;padding:16px 0 0;border-top:1px solid var(--line);display:grid;gap:8px;font-size:.88rem}
.legend p{margin:0 0 2px;color:var(--muted);font-size:.8rem;font-weight:600}
.legend div{display:flex;align-items:center;gap:10px;color:var(--muted)}
.legend b{font-weight:700;color:var(--c);background:color-mix(in srgb,var(--c) 12%,transparent);border-radius:8px;padding:2px 8px;min-width:3.2em;text-align:center}
.link{margin-top:14px;min-height:44px;padding:0;border:0;background:none;color:var(--faint);text-decoration:underline;text-underline-offset:3px;font-size:.85rem}
.link:hover{color:var(--b-bad)}

@media (max-width:560px){
  .controls{width:100%}
  .field{flex:1 1 100%}
  select{width:100%}
  .seg{display:flex}
  .seg button{flex:1;padding:0 6px}
  .layout{padding-top:20px}
}
@media (prefers-reduced-motion:reduce){
  .card,.bar i,.boxes .t i{transition:none}
  .card.deal{animation:none}
}
/* Nav + toolbar + setup */
:root{--sel:#10B981;--on-sel:#0F1729}
@media (prefers-color-scheme: light){:root:not([data-theme="dark"]){--sel:#047857;--on-sel:#FFFFFF}}
:root[data-theme="light"]{--sel:#047857;--on-sel:#FFFFFF}
.top{align-items:center}
.nav{display:flex;gap:4px;padding:3px;border:1px solid var(--line);border-radius:10px;background:var(--surface)}
.nav a{min-height:38px;display:inline-flex;align-items:center;gap:6px;padding:0 14px;border-radius:7px;color:var(--muted);font-weight:600;font-size:.9rem;text-decoration:none;transition:background-color .15s,color .15s}
.nav a:hover{color:var(--ink)}
.nav a[aria-current="page"]{background:var(--primary);color:var(--on-primary)}
.nav svg{width:16px;height:16px}
.toolbar{max-width:1120px;margin:0 auto;padding:20px clamp(16px,4vw,32px) 0;display:flex;flex-wrap:wrap;gap:12px 16px;align-items:flex-end}
.toolbar .grow{flex:1 1 auto}
.toolbar select{min-width:150px}
#f-topic{min-width:220px}
.scope{display:flex;align-items:center;gap:12px;flex-wrap:wrap;min-height:44px;padding:6px 6px 6px 14px;background:var(--surface);border:1px solid var(--line);border-radius:10px}
.scope b{font-weight:800}
.scope span{color:var(--muted);font-size:.88rem}
.btn-sm{min-height:34px;display:inline-flex;align-items:center;gap:6px;padding:0 12px;border:1px solid var(--line);border-radius:8px;background:transparent;font-size:.85rem;font-weight:600;color:var(--ink);text-decoration:none;transition:background-color .15s}
.btn-sm:hover{background:var(--inner)}
.btn-sm svg{width:15px;height:15px}
.layout{padding-top:24px}

.setup{max-width:880px;margin:0 auto;padding:36px clamp(16px,4vw,32px) 24px}
.setup h2{font-size:clamp(1.9rem,5vw,2.6rem);font-weight:900;letter-spacing:-.02em;margin:0 0 8px;line-height:1.15}
.lead{color:var(--muted);margin:0 0 24px;max-width:60ch}
.step{background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:20px;margin-bottom:14px}
.step-n{margin:0 0 2px;font-size:.72rem;font-weight:700;letter-spacing:.12em;text-transform:uppercase;color:var(--faint)}
.step h3{margin:0;font-size:1.1rem;font-weight:800}
.step-head{display:flex;justify-content:space-between;align-items:flex-end;gap:12px;flex-wrap:wrap;margin-bottom:14px}
.step>.step-n+h3{margin-bottom:14px}
.bulk{display:flex;gap:8px}
.levels{display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:10px}
@media (max-width:620px){.levels{grid-template-columns:repeat(2,minmax(0,1fr))}}
.lvl{text-align:left;padding:14px;border:1px solid var(--line);border-radius:10px;background:var(--inner);min-height:96px;display:flex;flex-direction:column;gap:2px;transition:background-color .15s,border-color .15s}
.lvl:hover{border-color:var(--muted)}
.lvl b{font-size:1.6rem;font-weight:900;line-height:1.1;letter-spacing:-.02em}
.lvl .d{font-size:.85rem;font-weight:600}
.lvl .s{font-size:.78rem;color:var(--muted)}
.lvl[aria-pressed="true"]{background:var(--primary);color:var(--on-primary);border-color:var(--primary)}
.lvl[aria-pressed="true"] .s{color:inherit;opacity:.72}
.topics{display:grid;grid-template-columns:repeat(auto-fill,minmax(230px,1fr));gap:10px}
.tp{display:flex;align-items:center;gap:12px;text-align:left;padding:12px 14px;min-height:66px;border:1px solid var(--line);border-radius:10px;background:var(--inner);transition:background-color .15s,border-color .15s}
.tp:hover{border-color:var(--muted)}
.tp .box{width:22px;height:22px;border-radius:6px;border:1.5px solid var(--faint);display:grid;place-items:center;flex:none;transition:background-color .15s,border-color .15s}
.tp .box svg{width:14px;height:14px;stroke-width:3;opacity:0}
.tp .txt{min-width:0}
.tp .txt b{display:block;font-weight:700;font-size:.95rem;line-height:1.3}
.tp .txt span{font-size:.8rem;color:var(--muted)}
.tp[aria-pressed="true"]{background:var(--b-done-bg);border-color:var(--sel)}
.tp[aria-pressed="true"] .box{background:var(--sel);border-color:var(--sel);color:var(--on-sel)}
.tp[aria-pressed="true"] .box svg{opacity:1}
.tp[aria-pressed="true"] .txt b{color:var(--b-done)}
.startbar{position:sticky;bottom:0;z-index:5;margin-top:8px;padding:16px 0 calc(16px + env(safe-area-inset-bottom,0px));background:linear-gradient(to top,var(--bg) 72%,transparent);display:flex;align-items:center;justify-content:space-between;gap:12px 20px;flex-wrap:wrap}
.startbar p{margin:0;color:var(--muted)}
.startbar p b{color:var(--ink)}
.startbar .btn{flex:0 0 auto;min-width:230px}
.btn:disabled{opacity:.4;cursor:not-allowed;transform:none}
[hidden]{display:none !important}
@media (max-width:560px){.startbar .btn{flex:1 1 100%}.toolbar select,#f-topic{min-width:0}}

/* Dùng chung: thông báo và toast */
.toast{position:fixed;left:50%;bottom:calc(20px + env(safe-area-inset-bottom,0px));transform:translateX(-50%) translateY(20px);opacity:0;pointer-events:none;background:var(--primary);color:var(--on-primary);padding:12px 18px;border-radius:10px;font-weight:600;font-size:.92rem;transition:opacity .2s,transform .2s;z-index:50;max-width:calc(100vw - 32px)}
.toast.show{opacity:1;transform:translateX(-50%) translateY(0)}
.toast.bad{background:var(--b-bad-bg);color:var(--b-bad);border:1px solid var(--b-bad)}
.notice{background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:28px 22px;text-align:center;color:var(--muted)}
.notice h3{margin:0 0 6px;color:var(--ink);font-weight:800}
@media (prefers-reduced-motion:reduce){.toast{transition:none}}