:root{
  --brand:#0EA5E9; --brand-deep:#0369A1; --brand-ink:#FFFFFF; --brand-soft:#E0F2FE;
  --ground:#F3F8FB; --paper:#FFFFFF; --ink:#0F2533; --muted:#5B7080; --line:#DCE7EE; --soft:#EEF5F9;
  --lv1:#10B981; --lv2:#3B82F6; --lv3:#F59E0B;
  --ok:#059669; --ok-soft:#D1FAE5; --warn:#B45309; --warn-soft:#FEF3C7; --bad:#E11D48; --bad-soft:#FFE4E6;
  --mm-root:#0EA5E9; --mm-root-ink:#FFFFFF;
  --mm1:#10B981; --mm1-ink:#FFFFFF; --mm2:#3B82F6; --mm2-ink:#FFFFFF; --mm3:#F59E0B; --mm3-ink:#3A2600;
  --mm4:#F43F5E; --mm4-ink:#FFFFFF; --mm5:#8B5CF6; --mm5-ink:#FFFFFF; --mm6:#06B6D4; --mm6-ink:#06303A;
  --shadow:0 1px 2px rgba(15,37,51,.06),0 8px 24px -12px rgba(15,37,51,.18);
  --r:12px;
  --font:"Be Vietnam Pro",system-ui,-apple-system,"Segoe UI",Roboto,sans-serif;
}
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){
    color-scheme:dark;
    --brand:#38BDF8; --brand-deep:#7DD3FC; --brand-ink:#04202E; --brand-soft:#0C3347;
    --ground:#0D1820; --paper:#13222C; --ink:#E4EEF4; --muted:#93A8B6; --line:#24394A; --soft:#172C3A;
    --lv1:#34D399; --lv2:#60A5FA; --lv3:#FBBF24;
    --ok:#34D399; --ok-soft:#0F3A2C; --warn:#FBBF24; --warn-soft:#3A2E0A; --bad:#FB7185; --bad-soft:#3F1621;
    --mm-root:#38BDF8; --mm-root-ink:#04202E;
    --mm1:#34D399; --mm1-ink:#062A1E; --mm2:#60A5FA; --mm2-ink:#081E3D; --mm3:#FBBF24; --mm3-ink:#3A2600;
    --mm4:#FB7185; --mm4-ink:#3D0812; --mm5:#A78BFA; --mm5-ink:#1E1040; --mm6:#22D3EE; --mm6-ink:#06303A;
    --shadow:0 1px 2px rgba(0,0,0,.3),0 8px 24px -12px rgba(0,0,0,.6);
  }
}
:root[data-theme="dark"]{
  color-scheme:dark;
  --brand:#38BDF8; --brand-deep:#7DD3FC; --brand-ink:#04202E; --brand-soft:#0C3347;
  --ground:#0D1820; --paper:#13222C; --ink:#E4EEF4; --muted:#93A8B6; --line:#24394A; --soft:#172C3A;
  --lv1:#34D399; --lv2:#60A5FA; --lv3:#FBBF24;
  --ok:#34D399; --ok-soft:#0F3A2C; --warn:#FBBF24; --warn-soft:#3A2E0A; --bad:#FB7185; --bad-soft:#3F1621;
  --mm-root:#38BDF8; --mm-root-ink:#04202E;
  --mm1:#34D399; --mm1-ink:#062A1E; --mm2:#60A5FA; --mm2-ink:#081E3D; --mm3:#FBBF24; --mm3-ink:#3A2600;
  --mm4:#FB7185; --mm4-ink:#3D0812; --mm5:#A78BFA; --mm5-ink:#1E1040; --mm6:#22D3EE; --mm6-ink:#06303A;
  --shadow:0 1px 2px rgba(0,0,0,.3),0 8px 24px -12px rgba(0,0,0,.6);
}

*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{margin:0;background:var(--ground);color:var(--ink);font-family:var(--font);font-size:15px;line-height:1.6}
a{color:var(--brand-deep);text-decoration:none}
a:hover{text-decoration:underline}
h1,h2,h3{line-height:1.25;text-wrap:balance;margin:0}
button,input,select,textarea{font:inherit;color:inherit}
:focus-visible{outline:2px solid var(--brand);outline-offset:2px}
.wrap{max-width:1160px;margin:0 auto;padding-inline:20px}
.num{font-variant-numeric:tabular-nums}
.muted{color:var(--muted)}
.small{font-size:13px}
.stack{display:flex;flex-direction:column;gap:16px}
.row{display:flex;flex-wrap:wrap;gap:10px;align-items:center}
.sp{flex:1}

/* ---------- demo banner & header ---------- */
.demo{background:var(--warn-soft);color:var(--warn);font-size:13px;padding:8px 0}
.demo .wrap{display:flex;flex-wrap:wrap;gap:6px 14px;align-items:center}
.demo b{color:var(--ink)}
.demo button{background:none;border:0;color:var(--warn);text-decoration:underline;cursor:pointer;padding:0;font-size:13px}
header.top{position:sticky;top:env(safe-area-inset-top,0px);z-index:20;background:color-mix(in srgb,var(--paper) 92%,transparent);backdrop-filter:blur(8px);border-bottom:1px solid var(--line)}
header.top .wrap{display:flex;align-items:center;gap:14px;min-height:62px;flex-wrap:wrap;padding-block:8px}
.logo{display:flex;align-items:center;gap:10px;font-weight:800;font-size:18px;color:var(--ink)}
.logo:hover{text-decoration:none}
.logo i{width:34px;height:34px;border-radius:10px;background:var(--brand);display:grid;place-items:center;color:var(--brand-ink);font-style:normal}
.nav{display:flex;gap:4px;flex-wrap:wrap}
.nav a{padding:6px 10px;border-radius:8px;color:var(--muted);font-weight:600;font-size:14px}
.nav a:hover,.nav a.on{background:var(--soft);color:var(--ink);text-decoration:none}
.who{margin-left:auto;display:flex;align-items:center;gap:8px;flex-wrap:wrap}
.chip-bal{display:inline-flex;align-items:center;gap:6px;background:var(--brand-soft);color:var(--brand-deep);font-weight:700;border-radius:999px;padding:5px 12px;font-size:14px}

/* ---------- buttons, forms ---------- */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;border:1px solid var(--line);background:var(--paper);border-radius:10px;padding:9px 16px;font-weight:600;font-size:14px;cursor:pointer;color:var(--ink);text-decoration:none;white-space:nowrap}
.btn:hover{border-color:var(--muted);text-decoration:none}
.btn.pri{background:var(--brand);border-color:var(--brand);color:var(--brand-ink)}
.btn.pri:hover{filter:brightness(1.05)}
.btn.ok{background:var(--ok);border-color:var(--ok);color:#fff}
.btn.ghost{background:transparent;border-color:transparent;color:var(--muted)}
.btn.bad{color:var(--bad);border-color:var(--bad-soft)}
.btn.sm{padding:6px 11px;font-size:13px;border-radius:8px}
.btn.lg{padding:12px 20px;font-size:15px}
.btn[disabled]{opacity:.55;cursor:not-allowed}
label.f{display:flex;flex-direction:column;gap:6px;font-weight:600;font-size:14px}
label.f span.h{font-weight:400;color:var(--muted);font-size:13px}
input.i,select.i,textarea.i{width:100%;border:1px solid var(--line);background:var(--paper);border-radius:10px;padding:10px 12px;font-size:15px}
textarea.i{min-height:120px;resize:vertical;line-height:1.5}
textarea.code{font-family:ui-monospace,Menlo,Consolas,monospace;font-size:13px;min-height:320px}
input.i:focus,select.i:focus,textarea.i:focus{border-color:var(--brand);outline:none;box-shadow:0 0 0 3px var(--brand-soft)}
.check{display:flex;gap:8px;align-items:center;font-weight:600;font-size:14px}
.err{background:var(--bad-soft);color:var(--bad);border-radius:10px;padding:10px 12px;font-size:14px}
.note{background:var(--soft);border-radius:10px;padding:10px 12px;font-size:14px;color:var(--muted)}

/* ---------- cards & badges ---------- */
.card{background:var(--paper);border:1px solid var(--line);border-radius:var(--r);padding:20px}
.badge{display:inline-flex;align-items:center;gap:4px;font-size:12px;font-weight:700;border-radius:999px;padding:3px 10px;white-space:nowrap}
.b-free{background:var(--ok-soft);color:var(--ok)}
.b-own{background:var(--brand-soft);color:var(--brand-deep)}
.b-price{background:var(--soft);color:var(--ink)}
.b-pend{background:var(--warn-soft);color:var(--warn)}
.b-bad{background:var(--bad-soft);color:var(--bad)}
.b-hide{background:var(--soft);color:var(--muted)}

/* ---------- home ---------- */
main{padding-block:28px 60px;min-height:60vh}
.hero{display:grid;grid-template-columns:1.05fr 1fr;gap:28px;align-items:center;margin-bottom:34px}
.hero h1{font-size:clamp(28px,4.2vw,44px);font-weight:800;letter-spacing:-.02em}
.hero h1 em{font-style:normal;color:var(--brand)}
.hero p.lead{font-size:17px;color:var(--muted);margin:14px 0 22px;max-width:52ch}
.hero .mini{background:var(--paper);border:1px solid var(--line);border-radius:16px;padding:10px;box-shadow:var(--shadow);overflow:hidden}
.hero .mini .mm-bar,.hero .mini .mm-hint{display:none}
.hero .mini .mm-stage{border:0;background-size:18px 18px}
.plans{display:grid;grid-template-columns:repeat(3,1fr);gap:14px;margin-bottom:40px}
.plan{background:var(--paper);border:1px solid var(--line);border-radius:var(--r);padding:16px 18px;display:flex;gap:14px;align-items:flex-start}
.plan .ic{flex:none;width:40px;height:40px;border-radius:10px;display:grid;place-items:center;font-size:20px}
.plan h3{font-size:16px}
.plan p{margin:2px 0 0;color:var(--muted);font-size:14px}
.sec-h{display:flex;align-items:baseline;gap:12px;margin:0 0 14px}
.sec-h h2{font-size:22px;font-weight:800}
.levels{display:flex;flex-direction:column;gap:28px}
.lvl h3{font-size:15px;font-weight:700;color:var(--muted);text-transform:uppercase;letter-spacing:.06em;margin-bottom:10px;display:flex;align-items:center;gap:8px}
.lvl h3 i{width:10px;height:10px;border-radius:3px;background:var(--c)}
.grades{display:grid;grid-template-columns:repeat(auto-fill,minmax(150px,1fr));gap:12px}
.grade{position:relative;background:var(--paper);border:1px solid var(--line);border-radius:var(--r);padding:14px 16px 16px;color:var(--ink);overflow:hidden;display:flex;flex-direction:column;gap:2px;min-height:122px}
.grade:hover{text-decoration:none;border-color:var(--c);box-shadow:var(--shadow)}
.grade::before{content:"";position:absolute;inset:0 0 auto 0;height:5px;background:var(--c)}
.grade .n{font-size:40px;font-weight:800;line-height:1;color:var(--c);margin-top:6px}
.grade .t{font-weight:700}
.grade .s{font-size:13px;color:var(--muted)}

/* ---------- grade page ---------- */
.crumb{font-size:14px;color:var(--muted);margin-bottom:10px}
.page-h{display:flex;flex-wrap:wrap;align-items:flex-end;gap:14px;margin-bottom:20px}
.page-h h1{font-size:clamp(26px,3.4vw,36px);font-weight:800}
.combo{display:flex;flex-wrap:wrap;gap:16px;align-items:center;background:linear-gradient(135deg,var(--brand-soft),var(--paper));border:1px solid var(--line);border-radius:var(--r);padding:18px 20px;margin-bottom:22px}
.combo .big{font-size:28px;font-weight:800;color:var(--brand-deep)}
.combo s{color:var(--muted)}
.subj{margin-bottom:22px}
.subj h2{font-size:18px;font-weight:700;margin-bottom:10px}
.lessons{background:var(--paper);border:1px solid var(--line);border-radius:var(--r);overflow:hidden}
.lrow{display:flex;align-items:center;gap:14px;padding:13px 16px;border-top:1px solid var(--line);color:var(--ink)}
.lrow:first-child{border-top:0}
.lrow:hover{background:var(--soft);text-decoration:none}
.lrow .o{flex:none;width:34px;height:34px;border-radius:9px;background:var(--soft);display:grid;place-items:center;font-weight:700;color:var(--muted)}
.lrow .tt{flex:1;min-width:0}
.lrow .tt b{display:block;font-weight:600}
.lrow .tt span{display:block;font-size:13px;color:var(--muted);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.empty{text-align:center;padding:40px 16px;color:var(--muted)}

/* ---------- lesson ---------- */
.lesson-h{margin-bottom:16px}
.lesson-h h1{font-size:clamp(24px,3.2vw,34px);font-weight:800;margin:6px 0 10px}
.mm-bar{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:10px}
.mm-bar button{border:1px solid var(--line);background:var(--paper);border-radius:8px;padding:6px 12px;font-weight:600;font-size:13px;cursor:pointer}
.mm-stage{background:var(--paper);border:1px solid var(--line);border-radius:var(--r);overflow:auto;background-image:radial-gradient(var(--line) 1px,transparent 1px);background-size:22px 22px}
.mm-stage svg{display:block;margin:0 auto}
.mm-node.tog{cursor:pointer}
.mm-hint{font-size:13px;color:var(--muted);margin:8px 0 0}
.two{display:grid;grid-template-columns:1.4fr 1fr;gap:18px;margin-top:18px}
.video{position:relative;aspect-ratio:16/9;max-width:100%;background:#000;border-radius:var(--r);overflow:hidden}
.video iframe{position:absolute;inset:0;width:100%;height:100%;border:0}
.video-empty{aspect-ratio:16/9;max-width:100%;border:1px dashed var(--line);border-radius:var(--r);display:grid;place-items:center;color:var(--muted);text-align:center;padding:16px;background:var(--paper)}
.notes ul{margin:8px 0 0;padding-left:20px;display:flex;flex-direction:column;gap:6px}
.lock{text-align:center;padding:36px 20px;background:var(--paper);border:1px solid var(--line);border-radius:var(--r)}
.lock .ic{width:60px;height:60px;border-radius:50%;background:var(--brand-soft);color:var(--brand-deep);display:grid;place-items:center;margin:0 auto 12px}
.lock h2{font-size:21px;font-weight:800}
.lock p{color:var(--muted);max-width:48ch;margin:8px auto 18px}
.lock .row{justify-content:center}
.pn{display:flex;justify-content:space-between;gap:12px;margin-top:22px;flex-wrap:wrap}

/* ---------- auth ---------- */
.auth{max-width:440px;margin:10px auto}
.auth h1{font-size:26px;font-weight:800;margin-bottom:4px}
.seg{display:grid;grid-template-columns:1fr 1fr;gap:8px}
.seg label{border:1px solid var(--line);border-radius:10px;padding:10px;text-align:center;cursor:pointer;font-weight:600;font-size:14px}
.seg input{position:absolute;opacity:0;pointer-events:none}
.seg label:has(input:checked){border-color:var(--brand);background:var(--brand-soft);color:var(--brand-deep)}

/* ---------- account / admin ---------- */
.side{display:grid;grid-template-columns:220px 1fr;gap:22px;align-items:start}
.tabs{display:flex;flex-direction:column;gap:2px;background:var(--paper);border:1px solid var(--line);border-radius:var(--r);padding:8px}
.tabs a{padding:9px 12px;border-radius:8px;color:var(--muted);font-weight:600;font-size:14px;display:flex;justify-content:space-between;gap:8px}
.tabs a:hover{background:var(--soft);text-decoration:none;color:var(--ink)}
.tabs a.on{background:var(--brand-soft);color:var(--brand-deep)}
.stat{display:flex;flex-direction:column;gap:2px}
.stat .v{font-size:30px;font-weight:800}
.stat .k{font-size:13px;color:var(--muted);font-weight:600}
.stats{display:grid;grid-template-columns:repeat(auto-fit,minmax(170px,1fr));gap:14px}
.tbl-wrap{overflow-x:auto;background:var(--paper);border:1px solid var(--line);border-radius:var(--r)}
table.t{width:100%;border-collapse:collapse;font-size:14px}
table.t th{text-align:left;font-size:12px;text-transform:uppercase;letter-spacing:.05em;color:var(--muted);font-weight:700;padding:10px 12px;border-bottom:1px solid var(--line);white-space:nowrap}
table.t td{padding:10px 12px;border-bottom:1px solid var(--line);vertical-align:middle}
table.t tr:last-child td{border-bottom:0}
td.r,th.r{text-align:right}
.plus{color:var(--ok);font-weight:700}
.minus{color:var(--bad);font-weight:700}
.amounts{display:grid;grid-template-columns:repeat(4,1fr);gap:8px}
.amounts button{border:1px solid var(--line);background:var(--paper);border-radius:10px;padding:12px 6px;font-weight:700;cursor:pointer}
.amounts button.on{border-color:var(--brand);background:var(--brand-soft);color:var(--brand-deep)}
.pay{display:grid;grid-template-columns:260px 1fr;gap:22px;align-items:start}
.qr{background:#fff;border:1px solid var(--line);border-radius:var(--r);padding:10px;text-align:center}
.qr img{width:100%;display:block}
.kv{display:grid;grid-template-columns:auto 1fr;gap:8px 14px;font-size:15px}
.kv dt{color:var(--muted)}
.kv dd{margin:0;font-weight:700;display:flex;gap:8px;align-items:center;flex-wrap:wrap}
.code{font-family:ui-monospace,Menlo,Consolas,monospace;background:var(--warn-soft);color:var(--ink);padding:2px 8px;border-radius:6px;letter-spacing:.04em}
.editor{display:grid;grid-template-columns:1fr 1fr;gap:18px;align-items:start}
.grid2{display:grid;grid-template-columns:1fr 1fr;gap:12px}
.grid3{display:grid;grid-template-columns:repeat(3,1fr);gap:12px}

/* ---------- modal & toast ---------- */
.modal{position:fixed;inset:0;background:rgba(8,20,28,.5);display:grid;place-items:center;z-index:50;padding:16px}
.modal .box{background:var(--paper);border-radius:16px;max-width:420px;width:100%;padding:22px;box-shadow:var(--shadow)}
.modal h3{font-size:19px;font-weight:800;margin-bottom:8px}
.modal .row{justify-content:flex-end;margin-top:18px}
.toast{position:fixed;left:50%;bottom:calc(20px + env(safe-area-inset-bottom,0px));transform:translateX(-50%);background:var(--ink);color:var(--paper);padding:11px 18px;border-radius:10px;font-weight:600;font-size:14px;z-index:60;box-shadow:var(--shadow);max-width:calc(100% - 32px)}
footer{border-top:1px solid var(--line);padding-block:22px;color:var(--muted);font-size:13px}
footer .wrap{display:flex;flex-wrap:wrap;gap:8px 20px;justify-content:space-between}
.spin{display:inline-block;width:18px;height:18px;border:2px solid var(--line);border-top-color:var(--brand);border-radius:50%;animation:sp .8s linear infinite}
@keyframes sp{to{transform:rotate(360deg)}}
@media (prefers-reduced-motion:reduce){.spin{animation-duration:3s}}

@media (max-width:860px){
  .hero,.two,.side,.pay,.editor{grid-template-columns:1fr}
  .plans{grid-template-columns:1fr}
  .tabs{flex-direction:row;flex-wrap:wrap}
  .amounts{grid-template-columns:repeat(2,1fr)}
  .grid3{grid-template-columns:1fr 1fr}
  .pay .qr{max-width:280px}
}
@media (max-width:480px){
  .grid2,.grid3{grid-template-columns:1fr}
  .nav{order:3;width:100%}
  .grades{grid-template-columns:repeat(2,1fr)}
}

/* ---------- v2: lesson sections, editor, 2FA ---------- */
.sh{font-size:18px;font-weight:700;margin:0}
.ssh{font-size:15px;font-weight:700;margin:6px 0 0;color:var(--muted)}
.lsec{display:flex;flex-direction:column;gap:10px;margin-bottom:6px}
.seg2{display:inline-flex;background:var(--soft);border-radius:9px;padding:3px;gap:2px}
.seg2 button{border:0;background:transparent;padding:5px 12px;border-radius:7px;font-weight:600;font-size:13px;cursor:pointer;color:var(--muted)}
.seg2 button.on{background:var(--paper);color:var(--ink);box-shadow:var(--shadow)}
.mm-img img{display:block;max-width:100%;height:auto;margin:0 auto;border-radius:var(--r);border:1px solid var(--line);background:#fff}
.rich h3{font-size:16px;margin:14px 0 6px}
.rich h3:first-child{margin-top:0}
.rich p{margin:0 0 10px}
.rich ul{margin:0 0 10px;padding-left:20px;display:flex;flex-direction:column;gap:4px}
.upl{display:grid;grid-template-columns:260px 1fr;gap:16px;align-items:start}
.upl-pv{min-height:140px;border:1px dashed var(--line);border-radius:10px;display:grid;place-items:center;padding:8px;background:var(--ground)}
.upl-pv img{max-width:100%;max-height:220px;display:block}
.soon{opacity:.7;display:flex;flex-direction:column;gap:8px;align-items:flex-start;border-style:dashed}
.savebar{position:sticky;bottom:calc(10px + env(safe-area-inset-bottom,0px));background:var(--paper);border:1px solid var(--line);border-radius:var(--r);padding:10px 12px;box-shadow:var(--shadow);z-index:5}
.otp{font-size:26px;letter-spacing:.4em;text-align:center;font-weight:700}
.steps{margin:0;padding-left:20px;display:flex;flex-direction:column;gap:10px}
@media (max-width:860px){.upl{grid-template-columns:1fr}}
.editor>*,.two>*,.side>*,.pay>*,.hero>*,.upl>*{min-width:0}
.qr-box svg{display:block;width:100%;height:auto}
.qr-cap{font-size:13px;color:#0F2533;margin-top:4px;line-height:1.4}
.paybox{max-width:560px}
.pay2{display:grid;grid-template-columns:200px 1fr;gap:16px;align-items:start}
.paystate{display:flex;gap:12px;align-items:flex-start;background:var(--soft);border-radius:10px;padding:12px;margin-top:14px}
.paystate .spin{flex:none;margin-top:3px}
.okdot{flex:none;width:26px;height:26px;border-radius:50%;background:var(--ok);color:#fff;display:grid;place-items:center;font-weight:800}
.modal .box{max-height:calc(100vh - 32px);overflow:auto}
@media (max-width:520px){.pay2{grid-template-columns:1fr}.pay2 .qr{max-width:240px;margin:0 auto}}
.paybox{max-width:620px}
.pay2{grid-template-columns:190px minmax(0,1fr)}
.pay2 .kv{grid-template-columns:auto minmax(0,1fr)}
.pay2 .kv dd{min-width:0;overflow-wrap:anywhere}
.modal .box.paybox{max-width:620px}

/* ---------- v3: mindmap cho điện thoại & máy tính ---------- */
.mm{display:flex;flex-direction:column;gap:10px}
.mm .mm-bar{display:flex;flex-wrap:wrap;gap:8px;align-items:center;margin:0}
.mm .mm-bar button{border:1px solid var(--line);background:var(--paper);border-radius:8px;padding:7px 12px;font-weight:600;font-size:13px;cursor:pointer;min-height:36px}
.mm .mm-bar .seg2{padding:3px}
.mm .mm-bar .seg2 button{border:0;min-height:32px}
.mm .mm-bar .seg2 button.on{background:var(--paper)}
.mm-maptools{display:inline-flex;gap:6px;flex-wrap:wrap}
.mm-maptools button[data-a="in"],.mm-maptools button[data-a="out"],.mm-maptools button[data-a="fit"]{width:38px;padding:0;font-size:17px}
.mm-fullbtn{margin-left:auto}
.mm .mm-stage{position:relative;overflow:hidden;touch-action:none;cursor:grab;user-select:none;-webkit-user-select:none;min-height:200px}
.mm .mm-stage:active{cursor:grabbing}
.mm .mm-stage svg{position:absolute;left:0;top:0;transform-origin:0 0;margin:0;max-width:none!important;width:auto}
.mm .mm-hint{margin:0}
.mm .mm-list{display:none}
.mm.is-list .mm-list{display:block}
.mm.is-list .mm-stage,.mm.is-list .mm-maptools{display:none}
.mm-mini .mm-stage{cursor:default;touch-action:auto;border:0;background-size:18px 18px}
.mm-mini .mm-stage svg{pointer-events:none}
/* danh sách */
.ml{display:flex;flex-direction:column;gap:12px}
.ml-root{background:var(--mm-root);color:var(--mm-root-ink);font-weight:800;font-size:19px;border-radius:14px;padding:14px 18px;text-align:center;box-shadow:0 4px 0 color-mix(in srgb,var(--mm-root) 30%,transparent)}
.ml-b{border:2px solid var(--c);border-radius:14px;background:color-mix(in srgb,var(--c) 7%,var(--paper));overflow:hidden}
.ml-b summary{list-style:none;cursor:pointer}
.ml-b summary::-webkit-details-marker{display:none}
.ml-h{background:var(--c);color:var(--ci);font-weight:700;font-size:17px;padding:12px 44px 12px 16px;position:relative}
.ml-h::after,.ml-i>details>summary::after{content:"–";position:absolute;right:14px;top:50%;transform:translateY(-50%);font-weight:800;font-size:18px}
details:not([open])>.ml-h::after,.ml-i>details:not([open])>summary::after{content:"+"}
.ml ul{list-style:none;margin:0;padding:8px 12px 12px 12px;display:flex;flex-direction:column;gap:8px}
.ml ul ul{padding:8px 0 2px 14px;border-left:3px solid color-mix(in srgb,var(--c) 45%,transparent);margin-left:6px;gap:6px}
.ml-i>span,.ml-i>details>summary{display:block;position:relative;font-size:16px;line-height:1.45;padding:9px 12px;border-radius:10px;background:var(--paper);border:1px solid color-mix(in srgb,var(--c) 35%,var(--line))}
.ml-i.d2>details>summary{font-weight:700;background:color-mix(in srgb,var(--c) 18%,var(--paper));padding-right:36px}
.ml-i.d3>span,.ml-i.d3>details>summary,.ml-i.d4>span{font-size:15px}
/* toàn màn hình */
.mm.mm-full{position:fixed;inset:0;z-index:100;background:var(--paper);padding:calc(10px + env(safe-area-inset-top,0px)) 10px calc(10px + env(safe-area-inset-bottom,0px));gap:8px}
.mm.mm-full .mm-stage{flex:1;height:auto!important;border-radius:12px}
.mm.mm-full .mm-hint{display:none}
html.mm-lock,html.mm-lock body{overflow:hidden}
@media (max-width:700px){
  .mm .mm-bar{gap:6px}
  .mm-fullbtn{margin-left:0}
  .mm-maptools button[data-a="fold"],.mm-maptools button[data-a="open"]{display:none}
}
.video.vert{aspect-ratio:9/16;max-height:80vh;width:auto;margin:0 auto;height:min(80vh,calc((100vw - 40px)*16/9))}
.jump{display:none}
@media (max-width:700px){
  main{padding-block:16px 40px}
  .wrap{padding-inline:16px}
  .lesson-h h1{font-size:23px}
  .jump{display:flex;gap:6px;position:sticky;top:calc(env(safe-area-inset-top,0px) + 64px);z-index:15;background:var(--ground);padding:8px 0;margin:0 0 8px;overflow-x:auto}
  .jump button{flex:1 0 auto;border:1px solid var(--line);background:var(--paper);border-radius:999px;padding:8px 9px;font-weight:700;font-size:13.5px;white-space:nowrap}
  .two{gap:14px}
  .rich{font-size:16px}
  .pn{flex-direction:column}
  .pn .btn{white-space:normal;text-align:left;justify-content:flex-start}
  .btn.lg{width:100%;white-space:normal}
  header.top .wrap{gap:8px;min-height:56px}
  .logo{font-size:16px}
  .who .btn.sm{padding:6px 9px}
}
@media (max-width:700px){
  header.top{position:static}
  .jump{top:env(safe-area-inset-top,0px)}
}

/* v4: cỡ chữ đồng đều trong dạng danh sách */
.ml-h{font-size:16px}
.ml-i>span,.ml-i>details>summary,.ml-i.d3>span,.ml-i.d3>details>summary,.ml-i.d4>span{font-size:16px}
.ml-root{font-size:20px}

/* v5: chọn môn học, học kì */
.grid4{display:grid;grid-template-columns:repeat(4,1fr);gap:12px}
.picks{display:flex;flex-direction:column;gap:10px;margin-bottom:18px;position:sticky;top:calc(env(safe-area-inset-top,0px) + 62px);z-index:10;background:var(--ground);padding-block:8px}
.chips{display:flex;gap:8px;overflow-x:auto;padding-bottom:2px;scrollbar-width:thin}
.chips button{flex:none;border:1px solid var(--line);background:var(--paper);border-radius:999px;padding:8px 14px;font-weight:700;font-size:14px;cursor:pointer;color:var(--ink);display:inline-flex;gap:6px;align-items:center}
.chips button.on{background:var(--brand);border-color:var(--brand);color:var(--brand-ink)}
.chips .cnt{font-size:12px;font-weight:700;background:var(--soft);color:var(--muted);border-radius:999px;padding:1px 7px}
.chips button.on .cnt{background:rgba(255,255,255,.25);color:inherit}
.small-chips button{padding:5px 12px;font-size:13px}
@media (max-width:860px){.grid4{grid-template-columns:1fr 1fr}}
@media (max-width:700px){.picks{top:env(safe-area-inset-top,0px)}}

/* ===== Bài tập tự chấm ===== */
.ex-sec .sh{margin-bottom:6px}
.ex{display:flex;flex-direction:column;gap:14px}
.ex-top{display:flex;flex-wrap:wrap;gap:6px 16px;align-items:center;justify-content:space-between;font-size:15px}
.ex-best{background:var(--ok-soft);color:var(--ok);border-radius:999px;padding:4px 12px;font-size:14px}
.ex-bar{height:8px;border-radius:99px;background:var(--soft);overflow:hidden}
.ex-bar i{display:block;height:100%;background:var(--brand);border-radius:99px;transition:width .25s}
.ex-list{list-style:none;margin:0;padding:0;display:flex;flex-direction:column;gap:14px}
.ex-q{background:var(--paper);border:1px solid var(--line);border-radius:var(--r);padding:16px 18px;scroll-margin-top:120px}
.ex-q.is-ok{border-color:var(--ok);box-shadow:inset 4px 0 0 var(--ok)}
.ex-q.is-bad{border-color:var(--bad);box-shadow:inset 4px 0 0 var(--bad)}
.ex-q.is-part{border-color:var(--warn);box-shadow:inset 4px 0 0 var(--warn)}
.ex-h{display:flex;gap:8px;align-items:center;margin-bottom:6px}
.ex-n{font-weight:800}
.ex-tag{font-size:12px;font-weight:700;border-radius:999px;padding:2px 10px;background:var(--brand-soft);color:var(--brand-deep)}
.ex-tag.t-ds{background:var(--warn-soft);color:var(--warn)}
.ex-tag.t-tl{background:var(--ok-soft);color:var(--ok)}
.ex-text{font-weight:600;line-height:1.5;margin-bottom:10px}
.ex-opts{display:grid;gap:8px}
.ex-opt{display:flex;gap:10px;align-items:flex-start;border:1.5px solid var(--line);border-radius:12px;padding:10px 12px;cursor:pointer;line-height:1.45;min-height:44px}
.ex-opt:hover{border-color:var(--brand)}
.ex-opt input{position:absolute;opacity:0;pointer-events:none}
.ex-opt:has(input:checked){border-color:var(--brand);background:var(--brand-soft)}
.ex-opt:has(input:focus-visible){outline:3px solid var(--brand);outline-offset:2px}
.ex-l{flex:none;width:26px;height:26px;border-radius:50%;display:inline-grid;place-items:center;font-weight:800;font-size:13px;background:var(--soft);color:var(--ink)}
.ex-opt:has(input:checked) .ex-l{background:var(--brand);color:var(--brand-ink)}
.ex-opt.ok{border-color:var(--ok);background:var(--ok-soft)}
.ex-opt.ok .ex-l{background:var(--ok);color:#fff}
.ex-opt.bad{border-color:var(--bad);background:var(--bad-soft)}
.ex-opt.bad .ex-l{background:var(--bad);color:#fff}
.ex-ds{display:grid;gap:8px}
.ex-st{display:grid;grid-template-columns:auto 1fr auto;gap:10px;align-items:center;border:1.5px solid var(--line);border-radius:12px;padding:8px 10px;line-height:1.45}
.ex-st.ok{border-color:var(--ok);background:var(--ok-soft)}
.ex-st.bad{border-color:var(--bad);background:var(--bad-soft)}
.ex-tf{display:flex;gap:6px}
.ex-tf label{cursor:pointer}
.ex-tf input{position:absolute;opacity:0;pointer-events:none}
.ex-tf span{display:inline-block;min-width:54px;text-align:center;border:1.5px solid var(--line);border-radius:999px;padding:7px 10px;font-weight:700;font-size:14px;background:var(--paper)}
.ex-tf input:checked+span{background:var(--brand);border-color:var(--brand);color:var(--brand-ink)}
.ex-tf input:focus-visible+span{outline:3px solid var(--brand);outline-offset:2px}
.ex-key{font-style:normal;font-weight:700;color:var(--ok);white-space:nowrap}
.ex-tl .i{max-width:320px;font-size:16px}
.ex-tl .i.ok{border-color:var(--ok);background:var(--ok-soft)}
.ex-tl .i.bad{border-color:var(--bad);background:var(--bad-soft)}
.ex-fb{margin-top:10px;border-top:1px dashed var(--line);padding-top:10px;font-size:15px;line-height:1.5}
.ex-verdict{font-weight:700}
.is-ok .ex-verdict{color:var(--ok)} .is-bad .ex-verdict{color:var(--bad)} .is-part .ex-verdict{color:var(--warn)}
.ex-expl{margin-top:4px;color:var(--ink)}
.ex-foot{display:flex;gap:10px;align-items:center;flex-wrap:wrap}
.ex-score{display:flex;gap:16px;align-items:center;flex-wrap:wrap;border-radius:var(--r);padding:16px 20px;border:2px solid var(--line);background:var(--paper)}
.ex-score.hi{border-color:var(--ok);background:var(--ok-soft)}
.ex-score.mid{border-color:var(--warn);background:var(--warn-soft)}
.ex-score.lo{border-color:var(--bad);background:var(--bad-soft)}
.ex-score>div:nth-child(2){flex:1;min-width:180px}
.ex-big{font-size:44px;font-weight:800;line-height:1}
.ex-big small{font-size:18px;font-weight:700;opacity:.7}
.b-score{background:var(--ok-soft);color:var(--ok)}
.ex-guide{font-size:13px;background:var(--ground);border:1px solid var(--line);border-radius:10px;padding:10px 12px;margin:0;white-space:pre-wrap;font-family:ui-monospace,Menlo,Consolas,monospace}
@media (max-width:560px){
  .ex-q{padding:14px 12px}
  .ex-st{grid-template-columns:auto 1fr}
  .ex-tf{grid-column:1/-1;justify-content:flex-end}
  .ex-tf span{min-width:72px;padding:9px 12px}
  .ex-big{font-size:36px}
  .ex-foot .btn{width:100%}
}

/* ===== Công thức (KaTeX) ===== */
.katex{font-size:1.08em}
.mm-fo{color:inherit}
.mm-fo .katex{font-size:1.02em}
.mm-fo .katex-display{margin:0}
.ml .katex,.ex .katex,.rich .katex{font-size:1.06em}
.mt-err{color:var(--bad);font-size:.9em}
/* Bài tập theo nhánh + nút đáp án */
.ex-grp{display:flex;flex-direction:column;gap:12px}
.ex-gh{margin:6px 0 0;font-size:17px;font-weight:800;display:flex;gap:8px;align-items:center;padding:8px 12px;border-radius:12px;background:var(--brand-soft);color:var(--brand-deep)}
.ex-ansbtn{font-size:13px;padding:5px 10px;min-height:32px;white-space:nowrap}
.ex-q.is-shown{border-color:var(--brand);box-shadow:inset 4px 0 0 var(--brand)}
.ex-q.is-seen{opacity:.92}
.ex-q.is-shown .ex-verdict{color:var(--brand-deep)}
.ex-key.f{color:var(--bad)}

/* Trang bài học: video → bài tập ở cột trái, nội dung chính ở cột phải (bám theo khi cuộn) */
.lgrid{grid-template-areas:"vid main" "ex main";grid-template-rows:auto 1fr;align-items:start}
.lgrid>#secVid{grid-area:vid}
.lgrid>#secMain{grid-area:main;position:sticky;top:84px;max-height:calc(100vh - 100px);overflow:auto;overscroll-behavior:contain}
.lgrid>#secEx{grid-area:ex;margin-top:4px}
@media (max-width:900px){
  .lgrid{grid-template-columns:1fr;grid-template-areas:"vid" "main" "ex";grid-template-rows:auto}
  .lgrid>#secMain{position:static;max-height:none;overflow:visible}
}
/* Thẻ ý cấp 2 trong sơ đồ (tiêu đề + gạch đầu dòng) */
.mm-card .mm-ct{margin-bottom:1px}
.mm-card .mm-cl{margin:0;padding-left:18px;list-style:none}
.mm-card .mm-cl li{position:relative;margin:1px 0}
/* Ý lớn: ô vuông màu đậm, chữ đậm, cách nhau rõ */
.mm-card>.mm-cl>li{font-weight:700;margin-top:5px}
.mm-card>.mm-cl>li:first-child{margin-top:2px}
.mm-card>.mm-cl>li::before{content:"";position:absolute;left:-15px;top:.42em;width:9px;height:9px;border-radius:2.5px;background:var(--mmc,currentColor)}
/* Ý nhỏ: thụt vào, có đường gióng màu nhạt bên trái, gạch ngắn thay chấm, chữ thường */
.mm-card .mm-cl ul{position:relative;margin:1px 0 2px 2px;padding-left:14px;list-style:none;font-weight:400}
.mm-card .mm-cl ul::before{content:"";position:absolute;left:0;top:3px;bottom:3px;width:2px;border-radius:2px;background:var(--mmc,currentColor);opacity:.35}
.mm-card .mm-cl ul>li{color:var(--ink-2,inherit);font-weight:400}
.mm-card .mm-cl ul>li::before{content:"";position:absolute;left:-9px;top:.72em;width:6px;height:2px;border-radius:1px;background:var(--mmc,currentColor);opacity:.8}
/* Sơ đồ trên trang bài học: rộng hơn khung chữ để tranh toàn cảnh to nhất */
@media (min-width:1200px){
  #secMap{width:min(calc(100vw - 48px),1560px);margin-left:calc(50% - min(50vw - 24px,780px))}
}
.mm-card .mm-cl.c2{column-count:2;column-gap:22px}
.mm-card .mm-cl.c2>li{break-inside:avoid}
/* Sơ đồ kiểu dọc (điện thoại): cuộn trang tự nhiên, không kéo/phóng */
.mm.mm-stack .mm-stage{touch-action:auto;cursor:default;user-select:text;-webkit-user-select:text}
.mm.mm-stack .mm-stage svg{margin:0 auto}
.mm.mm-stack .mm-maptools{display:none}
.mm.mm-full.mm-stack .mm-stage{overflow:auto;-webkit-overflow-scrolling:touch}
/* Toàn màn hình thật (máy tính) */
.mm:fullscreen{background:var(--paper);padding:10px;display:flex;flex-direction:column;gap:8px}
.mm:fullscreen .mm-stage{flex:1;height:auto!important}
/* Chế độ học từng nhánh trên điện thoại */
.mm-study[hidden]{display:none}
.mm.mm-studying{display:flex;flex-direction:column}
.mm.mm-studying .mm-stage,.mm.mm-studying .mm-list,.mm.mm-studying .mm-hint,.mm.mm-studying .seg2,.mm.mm-studying .mm-maptools{display:none!important}
.mm.mm-studying .mm-bar{margin:0}
.mm-study{flex:1;min-height:0;display:flex;flex-direction:column;gap:10px}
.st-top{display:flex;align-items:center;gap:8px;font-size:14px;color:var(--muted)}
.st-title{flex:1;min-width:0;white-space:nowrap;overflow:hidden;text-overflow:ellipsis;font-weight:700}
.st-pg{flex:none;font-weight:800;color:var(--ink);background:var(--soft);border-radius:999px;padding:3px 10px}
.st-body{flex:1;min-height:0;overflow:auto;-webkit-overflow-scrolling:touch;overscroll-behavior:contain;font-size:19px;line-height:1.55}
.st-root{background:var(--mm-root);color:var(--mm-root-ink);border-radius:18px;padding:18px;text-align:center;font-size:24px;font-weight:800;line-height:1.3}
.st-tip{color:var(--muted);font-size:15px;margin:14px 2px 8px}
.st-toc{display:flex;flex-direction:column;gap:10px}
.st-toc button{text-align:left;border:0;border-radius:14px;padding:14px 16px;font:inherit;font-size:18px;font-weight:700;background:var(--c);color:var(--ci);min-height:52px}
.st-card{border:2px solid var(--c);border-radius:18px;background:color-mix(in srgb,var(--c) 9%,var(--paper));padding:14px 16px 18px}
.st-h{margin:0 0 8px;font-size:22px;line-height:1.3;padding:10px 14px;border-radius:12px;background:var(--c);color:var(--ci)}
.st-l{margin:0;padding-left:22px}
.st-l li{margin:6px 0}
.st-l.d2>li{font-weight:700}
.st-l.d2>li::marker{color:var(--c)}
.st-l.d3{padding-left:20px}
.st-l.d3>li{font-weight:400}
.st-l .katex{font-size:1.05em}
.st-nav{display:flex;align-items:center;gap:8px;padding-top:4px}
.st-nav .btn{min-height:48px;min-width:96px;font-size:16px}
.st-dots{flex:1;display:flex;justify-content:center;gap:6px;flex-wrap:wrap}
.st-dots i{width:9px;height:9px;border-radius:50%;background:var(--line)}
.st-dots i.on{background:var(--c,var(--mm-root));transform:scale(1.35)}
/* Bấm nhánh để phóng to */
.mm-node.zoomable{cursor:zoom-in}
.mm .mm-tg{cursor:pointer}
.mm-stage svg.mm-anim{transition:transform .38s cubic-bezier(.2,.7,.2,1)}
.mm-back{position:absolute;top:10px;right:10px;z-index:3;border:0;border-radius:999px;padding:9px 16px;font:700 14px/1 var(--font);background:var(--ink);color:var(--paper);box-shadow:0 6px 18px rgba(0,0,0,.18);cursor:pointer}
.mm-back[hidden]{display:none}

/* ===== Hình minh họa ===== */
.fig-sec .sh{margin-bottom:4px}
.fig-grp{margin-top:12px}
.fig-gh{margin:0 0 8px;font-size:16px;font-weight:800;color:var(--brand-deep)}
.fig-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(300px,1fr));gap:14px}
.fig{margin:0;background:var(--paper);border:1px solid var(--line);border-radius:var(--r);overflow:hidden;cursor:zoom-in;display:flex;flex-direction:column;transition:box-shadow .15s,transform .15s}
.fig:hover,.fig:focus-visible{box-shadow:var(--shadow);transform:translateY(-2px);outline:none}
.fig-img{background:#fff;padding:6px;display:grid;place-items:center}
.fig-img img{width:100%;height:auto;display:block}
.fig figcaption{padding:10px 12px 12px;display:flex;flex-direction:column;gap:3px;font-size:14px;line-height:1.45;border-top:1px solid var(--line)}
.fig figcaption span{color:var(--muted)}
.fig-lb{position:fixed;inset:0;z-index:200;background:rgba(10,20,30,.72);display:grid;place-items:center;padding:14px}
.fig-lb-box{background:var(--paper);border-radius:16px;max-width:min(1100px,100%);max-height:100%;overflow:auto;padding:14px 16px;display:flex;flex-direction:column;gap:8px}
.fig-lb-h{display:flex;gap:12px;align-items:flex-start;justify-content:space-between;font-size:17px}
.fig-br{font-size:13px;color:var(--muted);font-weight:700}
.fig-lb-img{background:#fff;border-radius:10px}
.fig-lb-img img{width:100%;height:auto;display:block;max-height:78vh;object-fit:contain}
.fig-cap{margin:0;color:var(--ink);font-size:15px;line-height:1.5}
.st-figs{display:flex;flex-direction:column;gap:12px;margin-top:14px}
.st-fig{cursor:default}
.st-fig figcaption{font-size:15px}
@media (max-width:560px){.fig-grid{grid-template-columns:1fr}}

/* Hình minh họa nằm ngay trong thẻ nhánh của sơ đồ */
.mm-figs{display:flex;flex-wrap:wrap;gap:8px;margin-top:8px;justify-content:center}
.mm-fig{display:block;box-sizing:border-box;background:#fff;border:1.5px solid var(--mmc,var(--line));border-radius:8px;padding:2px;cursor:zoom-in;transition:box-shadow .15s}
.mm-fig:hover{box-shadow:0 2px 10px rgba(0,0,0,.18)}
/* Chế độ học (điện thoại): ý lớn ô vuông màu, ý nhỏ gạch ngắn + đường gióng */
.st-l{list-style:none}
.st-l li{position:relative}
.st-l.d2>li{margin-top:12px}
.st-l.d2>li::before{content:"";position:absolute;left:-19px;top:.45em;width:11px;height:11px;border-radius:3px;background:var(--c)}
.st-l.d3{position:relative;margin:4px 0 2px 2px;padding-left:18px}
.st-l.d3::before{content:"";position:absolute;left:0;top:4px;bottom:4px;width:3px;border-radius:2px;background:var(--c);opacity:.35}
.st-l.d3>li{margin:4px 0}
.st-l.d3>li::before{content:"";position:absolute;left:-12px;top:.78em;width:7px;height:2.5px;border-radius:2px;background:var(--c)}
/* Bài tập: chọn mức độ */
.ex-lvbox{margin:0 0 12px}
.ex-lvh{font-size:14px;color:var(--muted);margin:0 0 8px;font-weight:600}
.ex-lv{display:grid;grid-template-columns:repeat(4,1fr);gap:8px}
.ex-lv button{display:flex;flex-direction:column;align-items:center;gap:2px;border:2px solid var(--line);background:var(--paper);color:var(--ink);border-radius:14px;padding:10px 6px;font:inherit;cursor:pointer;min-height:58px;transition:border-color .15s,background .15s}
.ex-lv .lvn{font-weight:800;font-size:16px;white-space:nowrap}
.ex-lv .lvs{font-size:12.5px;color:var(--muted)}
.ex-lv button.lv1{--lc:#16a34a}.ex-lv button.lv2{--lc:#2563eb}.ex-lv button.lv3{--lc:#9333ea}.ex-lv button.lv4{--lc:#e11d48}
.ex-lv button:hover{border-color:var(--lc)}
.ex-lv button.on{border-color:var(--lc);background:color-mix(in srgb,var(--lc) 12%,var(--paper))}
.ex-lv button.on .lvn{color:var(--lc)}
.ex-acts{display:flex;gap:8px;flex-wrap:wrap}
@media (max-width:560px){.ex-lv{grid-template-columns:repeat(2,1fr)}.ex-lv .lvn{font-size:15px}}