/* Layout: app tra cứu — header + tab bar; Trang chủ dùng thẻ gradient cam – xanh; sổ tay = mục lục trái + thẻ kiến thức phải */
:root{
  --orange:#FF6A00; --orange-2:#FF4400; --orange-soft:#FFC7A6; --orange-tint:#FFF1E8;
  --blue:#1A9CF5; --blue-2:#0A66F0; --blue-soft:#A6D7FA; --blue-tint:#E9F5FF;
  --ink:#172033; --muted:#5A6577; --line:#E3E8F0; --bg:#F3F5F9; --surface:#FFFFFF; --surface-2:#F8FAFC;
  --ok:#14A058; --ok-tint:#E6F7EE; --bad:#E5383B; --bad-tint:#FDECEC;
  --fig:#1B2433;
  --f-display:"Lexend","Be Vietnam Pro",system-ui,sans-serif;
  --f-body:"Be Vietnam Pro",system-ui,-apple-system,"Segoe UI",sans-serif;
  --r:18px;
}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){
  --orange:#FF7A1A; --orange-2:#FF5A14; --orange-soft:#7A3512; --orange-tint:#2B1D14;
  --blue:#33A8F7; --blue-2:#1F78F2; --blue-soft:#163F6B; --blue-tint:#13243A;
  --ink:#EEF2F8; --muted:#9BA6B8; --line:#273042; --bg:#0E131C; --surface:#161D29; --surface-2:#1B2331;
  --ok:#3CCB7F; --ok-tint:#123326; --bad:#FF6B6E; --bad-tint:#3A1A1C; --fig:#E6EBF3; color-scheme:dark}}
:root[data-theme="dark"]{
  --orange:#FF7A1A; --orange-2:#FF5A14; --orange-soft:#7A3512; --orange-tint:#2B1D14;
  --blue:#33A8F7; --blue-2:#1F78F2; --blue-soft:#163F6B; --blue-tint:#13243A;
  --ink:#EEF2F8; --muted:#9BA6B8; --line:#273042; --bg:#0E131C; --surface:#161D29; --surface-2:#1B2331;
  --ok:#3CCB7F; --ok-tint:#123326; --bad:#FF6B6E; --bad-tint:#3A1A1C; --fig:#E6EBF3; color-scheme:dark}
*{box-sizing:border-box}
body{background:var(--bg);color:var(--ink);font-family:var(--f-body);font-size:16px;line-height:1.6;-webkit-font-smoothing:antialiased}
body::before{content:"";position:fixed;inset:0 0 auto;height:env(safe-area-inset-top,0px);z-index:30;background:var(--surface)}
.wrap{max-width:1200px;margin:0 auto;padding-left:max(16px,env(safe-area-inset-left,0px));padding-right:max(16px,env(safe-area-inset-right,0px))}
button{font:inherit;color:inherit;cursor:pointer}
:focus-visible{outline:3px solid var(--blue);outline-offset:2px;border-radius:8px}
h1,h2,h3{font-family:var(--f-display);text-wrap:balance;line-height:1.2;margin:0}

/* Header */
header.top{position:sticky;top:env(safe-area-inset-top,0px);z-index:20;background:var(--surface);border-bottom:1px solid var(--line)}
.top-row{display:flex;align-items:center;gap:16px;padding-block:12px}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none;color:inherit;flex-shrink:0}
.brand-mark{width:40px;height:40px;border-radius:12px;background:linear-gradient(140deg,var(--orange),var(--orange-2));display:grid;place-items:center;color:#fff;font-family:var(--f-display);font-weight:800;font-size:22px;box-shadow:0 6px 0 -1px var(--orange-soft)}
.brand-text{display:flex;flex-direction:column;line-height:1.05}
.brand-text b{font-family:var(--f-display);font-weight:800;font-size:21px;color:var(--orange);letter-spacing:-.01em}
.brand-text b span{color:var(--blue-2)}
.brand-text small{font-size:10.5px;font-weight:700;letter-spacing:.14em;color:var(--muted);text-transform:uppercase}
.search{flex:1;min-width:0;position:relative;max-width:520px;margin-left:auto}
.search input{width:100%;height:46px;border-radius:999px;border:2px solid var(--line);background:var(--surface-2);color:var(--ink);padding:0 44px 0 46px;font:inherit;font-size:15px}
.search input:focus{outline:none;border-color:var(--blue);background:var(--surface)}
.search svg{position:absolute;left:16px;top:50%;transform:translateY(-50%);color:var(--muted)}
.search .clear{position:absolute;right:8px;top:50%;transform:translateY(-50%);border:0;background:transparent;width:32px;height:32px;border-radius:50%;color:var(--muted);font-size:20px;line-height:1}
.theme-btn{border:2px solid var(--line);background:var(--surface);width:44px;height:44px;border-radius:50%;display:grid;place-items:center;flex-shrink:0}
nav.tabs{display:flex;gap:6px;overflow-x:auto;scrollbar-width:none;padding-bottom:10px}
nav.tabs::-webkit-scrollbar{display:none}
nav.tabs a{flex-shrink:0;text-decoration:none;color:var(--muted);font-weight:600;font-size:14.5px;padding:8px 14px;border-radius:999px;white-space:nowrap;display:flex;align-items:center;gap:6px}
nav.tabs a:hover{background:var(--surface-2);color:var(--ink)}
nav.tabs a.on{background:var(--ink);color:var(--surface)}
nav.tabs a.on.t-or{background:var(--orange);color:#fff}
nav.tabs a.on.t-bl{background:var(--blue-2);color:#fff}
.count{background:var(--orange);color:#fff;border-radius:999px;font-size:11.5px;padding:0 7px;line-height:18px;font-weight:700}

main{padding-block:28px 64px;min-height:70vh}

/* Home */
.hero{display:grid;grid-template-columns:1.1fr 1fr;gap:28px;align-items:center;margin-bottom:34px}
.eyebrow{display:inline-flex;align-items:center;gap:8px;font-weight:700;font-size:13px;letter-spacing:.08em;text-transform:uppercase;color:var(--orange)}
.eyebrow i{width:8px;height:8px;border-radius:50%;background:var(--orange);display:inline-block}
.hero h1{font-size:clamp(32px,5vw,54px);font-weight:800;letter-spacing:-.025em;margin:12px 0 14px}
.hero h1 .hl-o{color:var(--orange)}
.hero h1 .hl-b{color:var(--blue-2)}
.hero p{color:var(--muted);font-size:17px;max-width:52ch;margin:0 0 18px}
.chips{display:flex;flex-wrap:wrap;gap:8px}
.chip{border:2px solid var(--line);background:var(--surface);border-radius:999px;padding:6px 14px;font-size:14px;font-weight:600;color:var(--ink)}
.chip:hover{border-color:var(--orange);color:var(--orange)}
.formula-board{background:var(--surface);border-radius:24px;padding:22px;border:1px solid var(--line);position:relative;overflow:hidden}
.formula-board .fb-label{font-size:12px;font-weight:700;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);margin-bottom:6px;display:flex;justify-content:space-between;align-items:center;gap:8px}
.formula-board h3{font-size:19px;margin-bottom:6px}
.formula-board .fb-topic{font-size:13.5px;color:var(--muted);margin-bottom:10px}
.formula-board .fb-body{max-height:260px;overflow:auto}
.fb-actions{display:flex;gap:8px;margin-top:14px;flex-wrap:wrap}

.track-tiles{display:grid;grid-template-columns:1fr 1fr;gap:24px;margin-bottom:34px}
.tile{position:relative;text-decoration:none;color:#fff;border-radius:24px;padding:24px 24px 22px;min-height:230px;display:flex;flex-direction:column;overflow:hidden;isolation:isolate;transition:transform .18s ease}
.tile:hover{transform:translateY(-3px)}
.tile.or{background:linear-gradient(160deg,#FF7A0F 0%,#FF4A00 100%);box-shadow:0 14px 0 -4px var(--orange-soft)}
.tile.bl{background:linear-gradient(160deg,#1FA6F7 0%,#0A62EE 100%);box-shadow:0 14px 0 -4px var(--blue-soft)}
.tile .badges{display:flex;gap:8px;flex-wrap:wrap}
.badge{font-size:13px;font-weight:600;padding:4px 12px;border-radius:999px;background:rgba(0,0,0,.16)}
.badge.w{background:#fff;color:#172033}
.tile h2{font-size:clamp(26px,3.4vw,36px);font-weight:700;margin:18px 0 6px;letter-spacing:-.01em}
.tile p{margin:0;opacity:.95;max-width:34ch}
.tile .go{margin-top:auto;padding-top:18px;font-weight:700;display:flex;align-items:center;gap:8px}
.tile .deco{position:absolute;right:-14px;bottom:-18px;width:190px;height:190px;opacity:.22;z-index:-1}

.tools{display:grid;grid-template-columns:repeat(4,1fr);gap:16px}
.tool{background:var(--surface);border:1px solid var(--line);border-radius:var(--r);padding:18px;text-decoration:none;color:inherit;display:flex;flex-direction:column;gap:8px;transition:border-color .15s}
.tool:hover{border-color:var(--orange)}
.tool .ic{width:44px;height:44px;border-radius:14px;display:grid;place-items:center}
.tool .ic.o{background:var(--orange-tint);color:var(--orange)}
.tool .ic.b{background:var(--blue-tint);color:var(--blue-2)}
.tool b{font-family:var(--f-display);font-weight:700;font-size:17px}
.tool span{color:var(--muted);font-size:14px;line-height:1.45}
.sec-title{font-size:22px;font-weight:700;margin:0 0 14px}

/* Track view */
.banner{border-radius:24px;padding:22px 24px;color:#fff;margin-bottom:22px;position:relative;overflow:hidden;isolation:isolate}
.banner.or{background:linear-gradient(120deg,#FF7A0F,#FF4A00)}
.banner.bl{background:linear-gradient(120deg,#1FA6F7,#0A62EE)}
.banner .deco{position:absolute;right:10px;top:-30px;width:170px;height:170px;opacity:.2;z-index:-1}
.banner small{font-weight:700;letter-spacing:.08em;text-transform:uppercase;opacity:.9;font-size:12.5px}
.banner h1{font-size:clamp(24px,3.6vw,34px);font-weight:700;margin-top:4px}
.book{display:grid;grid-template-columns:290px minmax(0,1fr);gap:24px;align-items:start}
.toc{position:sticky;top:calc(env(safe-area-inset-top,0px) + 124px);background:var(--surface);border:1px solid var(--line);border-radius:var(--r);padding:12px;max-height:calc(100vh - 150px);overflow:auto}
.toc .part{font-size:11.5px;font-weight:700;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);padding:12px 10px 6px}
.toc button{display:flex;gap:10px;width:100%;text-align:left;border:0;background:transparent;padding:8px 10px;border-radius:12px;font-size:14.5px;line-height:1.35;align-items:flex-start}
.toc button .n{font-family:var(--f-display);font-weight:700;font-size:13px;min-width:30px;color:var(--muted);padding-top:1px;font-variant-numeric:tabular-nums}
.toc button:hover{background:var(--surface-2)}
.or-t .toc button.on{background:var(--orange-tint);color:var(--orange);font-weight:600}
.bl-t .toc button.on{background:var(--blue-tint);color:var(--blue-2);font-weight:600}
.or-t .toc button.on .n{color:var(--orange)} .bl-t .toc button.on .n{color:var(--blue-2)}
.toc-select{display:none;width:100%;height:48px;border-radius:14px;border:2px solid var(--line);background:var(--surface);color:var(--ink);font:inherit;font-weight:600;padding:0 12px;margin-bottom:16px}
.topic-head{margin-bottom:16px}
.topic-head .num{font-family:var(--f-display);font-weight:700;font-size:14px;letter-spacing:.06em}
.or-t .topic-head .num{color:var(--orange)} .bl-t .topic-head .num{color:var(--blue-2)}
.topic-head h2{font-size:clamp(22px,3vw,30px);font-weight:700;margin-top:2px}
.topic-head p{color:var(--muted);margin:4px 0 0;font-size:14.5px}
.cards{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px}
.kcard{background:var(--surface);border:1px solid var(--line);border-radius:var(--r);padding:18px 20px;min-width:0;scroll-margin-top:140px}
.kcard.wide{grid-column:1/-1}
.kcard.flash-hl{animation:hl 1.6s ease}
@keyframes hl{0%,40%{box-shadow:0 0 0 4px var(--orange)}100%{box-shadow:0 0 0 0 transparent}}
.kcard-h{display:flex;align-items:flex-start;justify-content:space-between;gap:10px;margin-bottom:8px}
.kcard-h h3{font-size:17.5px;font-weight:600}
.star{border:0;background:transparent;width:36px;height:36px;border-radius:50%;display:grid;place-items:center;color:var(--muted);flex-shrink:0;margin:-6px -8px 0 0}
.star:hover{background:var(--surface-2)}
.star.on{color:var(--orange)}
.star.on svg{fill:currentColor}
.pager{display:flex;justify-content:space-between;gap:12px;margin-top:22px;flex-wrap:wrap}
.btn{border:2px solid var(--line);background:var(--surface);border-radius:999px;padding:9px 18px;font-weight:600;font-size:14.5px;display:inline-flex;align-items:center;gap:8px;text-decoration:none;color:var(--ink)}
.btn:hover{border-color:var(--ink)}
.btn.pri{background:var(--orange);border-color:var(--orange);color:#fff}
.btn.pri:hover{background:var(--orange-2);border-color:var(--orange-2)}
.btn.blu{background:var(--blue-2);border-color:var(--blue-2);color:#fff}
.btn:disabled{opacity:.4;cursor:default}

/* Rich text */
.md p{margin:0 0 8px}
.md p:last-child,.md ul:last-child,.md ol:last-child{margin-bottom:0}
.md ul{margin:0 0 8px;padding-left:20px}
.md ul li{margin:3px 0}
.md ul li::marker{color:var(--orange)}
.bl-t .md ul li::marker{color:var(--blue-2)}
.md ol{margin:0 0 8px;padding:0;list-style:none;counter-reset:s}
.md ol li{counter-increment:s;position:relative;padding-left:34px;margin:6px 0}
.md ol li::before{content:counter(s);position:absolute;left:0;top:1px;width:24px;height:24px;border-radius:8px;background:var(--ink);color:var(--surface);font-family:var(--f-display);font-weight:700;font-size:13px;display:grid;place-items:center}
.mblock{overflow-x:auto;overflow-y:hidden;margin:6px 0 10px;padding:4px 0;text-align:center}
.tip,.note{border-radius:14px;padding:10px 14px;margin:8px 0;font-size:15px}
.tip{background:var(--blue-tint)}
.note{background:var(--orange-tint)}
.tip .tg,.note .tg{font-family:var(--f-display);font-weight:700;font-size:12px;letter-spacing:.06em;text-transform:uppercase;margin-right:6px}
.tip .tg{color:var(--blue-2)} .note .tg{color:var(--orange)}
.tbl{overflow-x:auto;margin:8px 0;border:1px solid var(--line);border-radius:12px}
.tbl table{border-collapse:collapse;width:100%;font-size:14.5px}
.tbl th,.tbl td{padding:8px 12px;border-bottom:1px solid var(--line);text-align:left;vertical-align:middle}
.tbl tr:last-child td{border-bottom:0}
.tbl th{background:var(--surface-2);font-weight:700;font-size:13.5px}
kbd{display:inline-block;font-family:var(--f-display);font-size:12.5px;font-weight:600;padding:1px 8px;border-radius:7px;background:var(--ink);color:var(--surface);box-shadow:0 2px 0 var(--muted);margin:0 1px;line-height:1.6}
.fig{margin:4px 0 10px;overflow-x:auto;text-align:center}
.fig svg{max-width:100%;height:auto}
mjx-container{max-width:100%}
mjx-container[display="true"]{margin:.3em 0 !important}

/* Examples */
.filter{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:18px}
.filter button{border:2px solid var(--line);background:var(--surface);border-radius:999px;padding:7px 16px;font-weight:600;font-size:14.5px}
.filter button.on{background:var(--ink);border-color:var(--ink);color:var(--surface)}
.ex-list{display:grid;gap:16px}
.ex{background:var(--surface);border:1px solid var(--line);border-radius:var(--r);overflow:hidden}
.ex-top{padding:18px 20px}
.ex-meta{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:8px}
.pill{font-size:12.5px;font-weight:700;padding:3px 10px;border-radius:999px}
.pill.o{background:var(--orange-tint);color:var(--orange)}
.pill.b{background:var(--blue-tint);color:var(--blue-2)}
.pill.g{background:var(--surface-2);color:var(--muted);border:1px solid var(--line)}
.ex h3{font-size:18px;font-weight:600;margin-bottom:8px}
.ex-sol{border-top:1px dashed var(--line);padding:16px 20px;background:var(--surface-2)}
.ans{display:inline-flex;gap:8px;align-items:center;font-weight:700;background:var(--ok-tint);color:var(--ok);border-radius:12px;padding:6px 12px;margin-top:10px}
.ex-bar{display:flex;gap:10px;align-items:center;padding:0 20px 18px;flex-wrap:wrap}

/* Quiz */
.quiz-wrap{max-width:760px}
.seg{display:inline-flex;background:var(--surface);border:2px solid var(--line);border-radius:999px;padding:4px;margin-bottom:16px;gap:2px}
.seg button{border:0;background:transparent;border-radius:999px;padding:7px 16px;font-weight:600;font-size:14.5px}
.seg button.on{background:var(--orange);color:#fff}
.qcard{background:var(--surface);border:1px solid var(--line);border-radius:24px;padding:22px}
.qprog{display:flex;justify-content:space-between;align-items:center;font-size:14px;color:var(--muted);font-weight:600;margin-bottom:10px;gap:10px}
.bar{height:8px;background:var(--surface-2);border-radius:999px;overflow:hidden;margin-bottom:16px;border:1px solid var(--line)}
.bar i{display:block;height:100%;background:linear-gradient(90deg,var(--orange),var(--orange-2));border-radius:999px;transition:width .3s}
.qtext{font-size:18px;font-weight:500;margin-bottom:14px}
.opts{display:grid;gap:10px}
.opt{display:flex;align-items:center;gap:12px;text-align:left;border:2px solid var(--line);background:var(--surface);border-radius:16px;padding:10px 14px;min-height:54px}
.opt .k{width:30px;height:30px;border-radius:10px;background:var(--surface-2);display:grid;place-items:center;font-family:var(--f-display);font-weight:700;flex-shrink:0;border:1px solid var(--line)}
.opt:hover:not(:disabled){border-color:var(--orange)}
.opt.ok{border-color:var(--ok);background:var(--ok-tint)}
.opt.ok .k{background:var(--ok);color:#fff;border-color:var(--ok)}
.opt.bad{border-color:var(--bad);background:var(--bad-tint)}
.opt.bad .k{background:var(--bad);color:#fff;border-color:var(--bad)}
.opt:disabled{cursor:default}
.qfb{margin-top:14px;border-radius:14px;padding:12px 14px;background:var(--surface-2)}
.qfb b{font-family:var(--f-display)}
.qfb.ok b{color:var(--ok)} .qfb.bad b{color:var(--bad)}
.qnav{display:flex;justify-content:flex-end;margin-top:16px;gap:10px}
.score{text-align:center;padding:10px 0}
.score .big{font-family:var(--f-display);font-weight:800;font-size:64px;color:var(--orange);line-height:1}
.flash{perspective:1400px}
.flash-card{background:var(--surface);border:1px solid var(--line);border-radius:24px;padding:24px;min-height:300px;cursor:pointer;position:relative}
.flash-card .face-front{display:flex;flex-direction:column;justify-content:center;align-items:flex-start;min-height:250px}
.flash-card .face-front h3{font-size:clamp(22px,3.4vw,30px);font-weight:700;margin:8px 0}
.flash-card .hint{color:var(--muted);font-size:14px;margin-top:10px}
.flash-card.flipped{border-color:var(--orange)}

.empty{background:var(--surface);border:2px dashed var(--line);border-radius:var(--r);padding:30px;text-align:center;color:var(--muted)}
.empty b{display:block;font-family:var(--f-display);color:var(--ink);font-size:18px;margin-bottom:6px}
.res-item{display:block;width:100%;text-align:left;background:var(--surface);border:1px solid var(--line);border-radius:16px;padding:14px 16px;margin-bottom:10px}
.res-item:hover{border-color:var(--orange)}
.res-item .rt{font-weight:600;font-size:16px;margin:4px 0 2px}
.res-item .rs{color:var(--muted);font-size:14px;overflow:hidden;text-overflow:ellipsis;display:-webkit-box;-webkit-line-clamp:2;-webkit-box-orient:vertical}
mark{background:var(--orange-tint);color:var(--orange);border-radius:4px;padding:0 2px}
footer{color:var(--muted);font-size:13px;padding-block:26px 40px;border-top:1px solid var(--line)}

/* Chọn khối, lớp */
.grade-pick{background:var(--surface);border:1px solid var(--line);border-radius:24px;padding:20px 22px 22px;margin-bottom:30px}
.gp-head{display:flex;justify-content:space-between;align-items:baseline;gap:12px;flex-wrap:wrap;margin-bottom:14px}
.gp-head h2{font-size:22px;font-weight:700}
.gp-head span{color:var(--muted);font-size:14px}
.gp-groups{display:grid;grid-template-columns:5fr 4fr 3fr;gap:18px}
.gp-label{font-family:var(--f-display);font-weight:700;font-size:13px;letter-spacing:.08em;text-transform:uppercase;margin-bottom:8px;display:flex;align-items:center;gap:8px}
.gp-label.cs{color:var(--orange)} .gp-label.pt{color:var(--blue-2)}
.gp-label i{flex:1;height:2px;border-radius:2px;background:currentColor;opacity:.25}
.gp-row{display:grid;gap:10px}
.gp-row.n5{grid-template-columns:repeat(5,1fr)} .gp-row.n4{grid-template-columns:repeat(4,1fr)} .gp-row.n3{grid-template-columns:repeat(3,1fr)}
.gbtn{border:2px solid var(--line);border-radius:18px;background:var(--surface);padding:12px 4px 10px;display:flex;flex-direction:column;align-items:center;gap:4px;text-decoration:none;color:var(--ink);transition:transform .15s,border-color .15s,background .15s}
.gbtn:hover{transform:translateY(-2px)}
.gbtn small{font-size:11.5px;font-weight:700;letter-spacing:.06em;text-transform:uppercase;color:var(--muted)}
.gbtn b{font-family:var(--f-display);font-weight:800;font-size:34px;line-height:1}
.gbtn em{font-style:normal;font-size:12px;color:var(--muted);font-weight:600}
.gbtn.cs b{color:var(--orange)} .gbtn.pt b{color:var(--blue-2)}
.gbtn.cs:hover{border-color:var(--orange);background:var(--orange-tint)}
.gbtn.pt:hover{border-color:var(--blue-2);background:var(--blue-tint)}
.gbtn.on.cs{background:linear-gradient(160deg,#FF7A0F,#FF4A00);border-color:transparent;box-shadow:0 8px 0 -2px var(--orange-soft)}
.gbtn.on.pt{background:linear-gradient(160deg,#1FA6F7,#0A62EE);border-color:transparent;box-shadow:0 8px 0 -2px var(--blue-soft)}
.gbtn.on b,.gbtn.on small,.gbtn.on em{color:#fff}
.grade-sel{height:44px;border-radius:999px;border:2px solid var(--line);background:var(--surface);color:var(--ink);font:inherit;font-weight:700;font-size:14.5px;padding:0 12px;flex-shrink:0}
.grade-sel:focus{outline:none;border-color:var(--orange)}
.gswitch{display:flex;gap:6px;flex-wrap:wrap;margin-top:14px}
.gswitch a{background:rgba(255,255,255,.2);color:#fff;border-radius:999px;padding:5px 14px;font-weight:700;font-size:14px;text-decoration:none}
.gswitch a:hover{background:rgba(255,255,255,.32)}
.gswitch a.on{background:#fff;color:#172033}
.gswitch .sep{width:1px;background:rgba(255,255,255,.4);margin:4px 4px}
.filter .lbl{align-self:center;font-weight:700;font-size:13px;color:var(--muted);margin-right:2px}
@media (max-width:640px){.gp-groups{grid-template-columns:1fr}.grade-sel{display:none}.gbtn b{font-size:30px}}
.brand-logo{height:28px;width:auto;display:block}
.brand-sub{font-family:var(--f-display);font-size:11px;font-weight:700;letter-spacing:.06em;text-transform:uppercase;color:var(--muted);line-height:1.15;padding-left:10px;border-left:2px solid var(--line)}
.foot{display:flex;gap:14px;align-items:center;flex-wrap:wrap}
.foot b{color:var(--ink);font-weight:600}
.foot-logo{height:24px;width:auto}
@media (max-width:640px){.brand-sub{display:none}.brand-logo{height:22px}}
/* Khối Tiểu học: cam vàng cùng họ màu thương hiệu */
:root{--amber:#FFA21A;--amber-2:#FF7A00;--amber-ink:#B85C00;--amber-tint:#FFF4E0;--amber-soft:#FFD9A0}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){--amber-ink:#FFB547;--amber-tint:#2E2312;--amber-soft:#7A4A0E}}
:root[data-theme="dark"]{--amber-ink:#FFB547;--amber-tint:#2E2312;--amber-soft:#7A4A0E}
.tile.yl{background:linear-gradient(160deg,#FFB21F 0%,#FF7A00 100%);box-shadow:0 14px 0 -4px var(--amber-soft)}
.banner.yl{background:linear-gradient(120deg,#FFB21F,#FF7A00)}
.gp-label.th{color:var(--amber-ink)}
.gbtn.th b{color:var(--amber-ink)}
.gbtn.th:hover{border-color:var(--amber);background:var(--amber-tint)}
.gbtn.on.th{background:linear-gradient(160deg,#FFB21F,#FF7A00);border-color:transparent;box-shadow:0 8px 0 -2px var(--amber-soft)}
.yl-t .toc button.on{background:var(--amber-tint);color:var(--amber-ink);font-weight:600}
.yl-t .toc button.on .n,.yl-t .topic-head .num{color:var(--amber-ink)}
.yl-t .md ul li::marker{color:var(--amber-2)}
.pill.y{background:var(--amber-tint);color:var(--amber-ink)}
nav.tabs a.on.t-yl{background:var(--amber-2);color:#fff}
.btn.yel{background:var(--amber-2);border-color:var(--amber-2);color:#fff}
.track-tiles{grid-template-columns:repeat(3,1fr)}
@media (max-width:1100px){.gp-groups{grid-template-columns:1fr}}
@media (max-width:1000px){.track-tiles{grid-template-columns:1fr}}
@media (max-width:640px){.gp-row.n5{grid-template-columns:repeat(5,1fr);gap:6px}.gbtn{padding:10px 2px 8px}.gbtn em{display:none}}
.md mjx-container.mx-wide{display:block;overflow-x:auto;overflow-y:hidden;max-width:100%;padding:2px 0}
.cards{align-items:start}
/* Logo Hoctoan.online */
.logo-mark{display:block;flex-shrink:0;border-radius:11px;box-shadow:0 5px 0 -1px var(--orange-soft)}
.logo-word{font-family:var(--f-display);font-weight:800;font-size:23px;letter-spacing:-.02em;color:var(--ink);line-height:1}
.logo-word em{font-style:normal;color:var(--orange);font-weight:700;font-size:.78em;letter-spacing:0}
.logo-word.sm{font-size:18px}
.foot-brand{display:flex;align-items:center;gap:8px}
.foot-brand .logo-mark{box-shadow:none}
@media (max-width:640px){.logo-word{font-size:19px}.logo-mark{width:30px;height:30px}}
@media (max-width:400px){.top-row .logo-word{display:none}}
/* Hộp chọn lớp lần đầu */
.gp-modal{position:fixed;inset:0;z-index:50;background:rgba(15,20,30,.55);display:flex;align-items:center;justify-content:center;padding:max(16px,env(safe-area-inset-top,0px)) max(16px,env(safe-area-inset-right,0px)) max(16px,env(safe-area-inset-bottom,0px)) max(16px,env(safe-area-inset-left,0px));overflow:auto}
.gp-modal-card{background:var(--surface);border-radius:24px;padding:24px;max-width:860px;width:100%;box-shadow:0 20px 60px rgba(0,0,0,.25);max-height:100%;overflow:auto}
.gp-modal-card .logo-row{display:flex;align-items:center;gap:10px;margin-bottom:14px}
.gp-modal-card h2{font-size:clamp(22px,3vw,28px);font-weight:800;margin-bottom:6px}
.gp-modal-card p{color:var(--muted);margin:0 0 16px}
.gp-modal .gp-groups{grid-template-columns:1fr}
.gp-modal .gbtn{cursor:pointer}

/* Đề cương ôn thi */
.cta-app{display:flex;gap:12px;flex-wrap:wrap;align-items:center;justify-content:space-between;background:var(--surface);border:1px dashed var(--line);border-radius:16px;padding:14px 16px}
.tabs a.t-dc{position:relative}
.dc-grades{display:flex;flex-wrap:wrap;gap:0 22px;margin-bottom:6px}
.dc-grades .filter{margin-bottom:12px}
.dc-grades .filter button{min-width:44px;padding:7px 12px}
.dc-periods{display:flex;flex-wrap:wrap;gap:10px;margin:0 0 20px}
.dc-per{display:flex;flex-direction:column;align-items:flex-start;gap:1px;border:2px solid var(--line);background:var(--surface);color:var(--ink);border-radius:14px;padding:9px 16px 8px;font-weight:700;font-family:var(--f-display);font-size:15px;text-decoration:none;cursor:pointer;line-height:1.25}
.dc-per small{font-family:var(--f-body,inherit);font-weight:600;font-size:12px;color:var(--muted)}
.dc-per.ok small{color:var(--orange)}
.dc-per.ok small::before{content:"";display:inline-block;width:7px;height:7px;border-radius:50%;background:currentColor;margin-right:5px;vertical-align:1px}
.dc-per.soon{border-style:dashed}
.dc-per.on{border-color:var(--orange);background:var(--orange-tint)}
.dc-per.on.soon{border-color:var(--muted);background:var(--surface-2)}
a.dc-per:hover{border-color:var(--orange)}
.dc-head{display:flex;flex-wrap:wrap;gap:8px 16px;align-items:baseline;justify-content:space-between;margin-bottom:12px}
.dc-head h3,.dc-head h2{font-size:20px;font-weight:700;margin:0}
.dc-link{font-size:14px;font-weight:600;color:var(--blue-2);text-decoration:none}
.dc-note{color:var(--muted);margin:0 0 14px;max-width:75ch}
.dc-files{display:grid;grid-template-columns:repeat(auto-fill,minmax(270px,1fr));gap:12px;margin-bottom:18px}
.dc-file{display:flex;gap:14px;align-items:center;background:var(--surface);border:1px solid var(--line);border-radius:18px;padding:14px 16px}
.dc-ic{position:relative;flex:none;width:50px;height:58px;border-radius:12px;display:grid;place-items:center;padding-bottom:12px}
.dc-ic.o{background:var(--orange-tint);color:var(--orange)}.dc-ic.b{background:var(--blue-tint);color:var(--blue-2)}
.dc-ic i{position:absolute;bottom:6px;left:0;right:0;text-align:center;font-style:normal;font-weight:800;font-size:10.5px;letter-spacing:.06em}
.dc-fmeta{min-width:0}.dc-fmeta b{display:block;font-weight:700;line-height:1.3}.dc-fmeta small{color:var(--muted);font-size:13px}
.dc-act{display:flex;gap:8px;margin-top:8px;flex-wrap:wrap}.dc-act .btn{padding:7px 14px;font-size:14px}
.dc-groups{display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));gap:12px}
.dc-group{background:var(--surface);border:1px solid var(--line);border-radius:18px;padding:16px 18px}
.dc-group h3{font-size:13px;font-weight:700;letter-spacing:.08em;text-transform:uppercase;color:var(--orange);margin:0 0 8px}
.dc-group ul{margin:0;padding-left:20px}.dc-group li{margin:5px 0}.dc-group li::marker{color:var(--orange)}
.dc-soon{display:flex;flex-direction:column;align-items:center;gap:4px;text-align:center;background:var(--surface);border:2px dashed var(--line);border-radius:var(--r);padding:30px 20px;color:var(--muted)}
.dc-soon b{font-family:var(--f-display);font-size:18px;color:var(--ink)}
.dc-soon span{display:inline-block;background:var(--surface-2);color:var(--ink);font-weight:700;font-size:13px;border-radius:999px;padding:4px 12px;margin:4px 0}
.dc-matrix{overflow-x:auto;background:var(--surface);border:1px solid var(--line);border-radius:18px;margin-bottom:24px}
.dc-matrix table{border-collapse:collapse;width:100%;min-width:640px;font-size:14px}
.dc-matrix th,.dc-matrix td{padding:10px 12px;border-bottom:1px solid var(--line);text-align:left;vertical-align:middle}
.dc-matrix tr:last-child td{border-bottom:0}
.dc-matrix th{font-size:12.5px;text-transform:uppercase;letter-spacing:.06em;color:var(--muted);font-weight:700}
.dc-matrix td:first-child{font-weight:700;white-space:nowrap}
.dc-matrix a.ok{display:inline-block;background:var(--orange);color:#fff;font-weight:700;border-radius:999px;padding:4px 12px;text-decoration:none;font-size:13px}
.dc-matrix .soon{color:var(--muted);font-size:13px}
.dc-matrix .ex{font-size:13px;color:var(--muted)}
@media (max-width:700px){.dc-files{grid-template-columns:1fr}.dc-groups{grid-template-columns:1fr}}
.filter a.fbtn{border:2px solid var(--line);background:var(--surface);border-radius:999px;padding:7px 12px;min-width:44px;text-align:center;font-weight:600;font-size:14.5px;color:var(--ink);text-decoration:none}
.filter a.fbtn.on{background:var(--ink);border-color:var(--ink);color:var(--surface)}
.filter a.fbtn:hover:not(.on){border-color:var(--orange)}
details.sol>summary{cursor:pointer;list-style:none;display:flex}details.sol>summary::-webkit-details-marker{display:none}
details.sol[open]>summary .lbl-open{display:none}details.sol:not([open])>summary .lbl-close{display:none}
details.sol[open]>summary .btn{background:var(--surface);color:var(--ink);border-color:var(--line);box-shadow:none}
.md .cols{display:grid;gap:4px 22px;margin:6px 0}
.md .cols.c2{grid-template-columns:repeat(2,minmax(0,1fr))}.md .cols.c3{grid-template-columns:repeat(3,minmax(0,1fr))}.md .cols.c4{grid-template-columns:repeat(4,minmax(0,1fr))}
.md .cols>div{min-width:0;padding:3px 0}
.dc-img{text-align:center;margin:10px 0}
.dc-img img{max-width:min(100%,420px);height:auto;background:#fff;border-radius:12px;padding:8px}
.dc-toc{display:flex;flex-wrap:wrap;gap:8px;margin:0 0 18px}
.dc-toc a{font-size:13.5px;font-weight:600;text-decoration:none;color:var(--ink);background:var(--surface);border:1.5px solid var(--line);border-radius:999px;padding:6px 12px}
.dc-toc a.sec{background:var(--ink);color:var(--surface);border-color:var(--ink)}
.dc-toc a:hover{border-color:var(--orange)}
.dc-sec{font-size:clamp(19px,2.6vw,23px);font-weight:700;margin:26px 0 12px;padding-left:12px;border-left:5px solid var(--orange);scroll-margin-top:120px}
.dc-dang{font-size:13.5px;font-weight:800;letter-spacing:.07em;text-transform:uppercase;color:var(--blue-2);margin:20px 0 10px;scroll-margin-top:120px}
.dc-kt{background:var(--surface);border:1px solid var(--line);border-radius:18px;padding:14px 20px}
.dc-detail .ex{margin-bottom:14px}
.dc-bh{display:flex;gap:10px;align-items:baseline;font-size:16.5px;font-weight:600;line-height:1.45;margin:0 0 6px}
.dc-bn{flex:none;font-family:var(--f-display);font-weight:700;font-size:13.5px;border-radius:8px;padding:3px 9px;color:#fff;background:var(--orange)}
.dc-bn.b{background:var(--blue-2)}.dc-bn.y{background:var(--amber-2)}
@media (max-width:700px){.md .cols.c3,.md .cols.c4{grid-template-columns:repeat(2,minmax(0,1fr))}.md .cols.c2{grid-template-columns:1fr}}
.dc-bai .md p,.dc-bai .md .cols>div{line-height:2}
.dc-bai .ex-sol .md p{margin:6px 0 10px}
.dc-print-bar{display:flex;gap:10px;flex-wrap:wrap;justify-content:flex-end;margin:-6px 0 14px}
.dc-print-bar .btn{display:inline-flex;align-items:center;gap:8px}
.print-head{display:none}
@media print{
  @page{size:A4;margin:14mm 13mm 16mm;@bottom-center{content:"hoctoan.online  ·  Trang " counter(page) "/" counter(pages);font:9pt "Be Vietnam Pro",sans-serif;color:#777}}
  html,body{background:#fff!important;color:#111!important}
  body:has(.dc-detail) header.top,body:has(.dc-detail) footer,body:has(.dc-detail) .gp-modal,body:has(.dc-detail) #main>:not(.dc-detail),body:has(.dc-detail) section[aria-label="Mục lục toàn bộ"]{display:none!important}
  body:has(.dc-detail) #main{padding:0!important;margin:0!important;max-width:none!important}
  .dc-print-bar,.dc-toc,details.sol>summary{display:none!important}
  .print-head{display:block;margin-bottom:12px}
  .ph-row{display:flex;align-items:center;justify-content:space-between;gap:16px;padding-bottom:10px;border-bottom:3px solid #FF6A00}
  .ph-brand{display:flex;align-items:center;gap:8px;font-family:Lexend,sans-serif;font-weight:700;font-size:17pt;color:#111}
  .ph-brand em{font-style:normal;color:#FF6A00}
  .ph-title{text-align:right;font-family:Lexend,sans-serif;line-height:1.3}
  .ph-title b{display:block;font-size:13pt;color:#111}.ph-title span{font-size:10.5pt;color:#FF6A00;font-weight:600}
  .ph-info{display:flex;justify-content:space-between;font-size:10.5pt;margin-top:10px;color:#111}
  .dc-sec{color:#111!important;border-left-color:#FF6A00!important;font-size:14pt!important;margin:14px 0 8px!important;break-after:avoid}
  .dc-dang{color:#FF6A00!important;font-size:10.5pt!important;margin:12px 0 6px!important;break-after:avoid}
  .dc-kt{border:1px solid #ddd!important;padding:8px 14px!important}
  .dc-detail .ex{border:0!important;box-shadow:none!important;background:none!important;margin:0 0 10px!important;padding:0!important}
  .dc-detail .ex-top{padding:0!important;break-inside:avoid}
  .dc-bh{font-size:11.5pt!important;color:#111!important}
  .dc-bn{background:#111!important;color:#fff!important;-webkit-print-color-adjust:exact;print-color-adjust:exact}
  .dc-bn::after{content:"";display:inline-block;width:6px;height:6px;border-radius:50%;background:#FF6A00;margin-left:6px;vertical-align:1px}
  .dc-detail .md{font-size:11pt;color:#111}
  .dc-img img{max-width:62mm!important;padding:0!important}
  body:not(.print-sol) .dc-detail details.sol{display:none!important}
  body.print-sol .dc-detail details.sol .ex-sol{display:block!important;border:0!important;border-left:3px solid #FF6A00!important;background:#FFF6EF!important;padding:6px 12px!important;margin-top:6px;-webkit-print-color-adjust:exact;print-color-adjust:exact}
  body.print-sol .dc-detail details.sol .ex-sol::before{content:"Lời giải";display:block;font-weight:700;color:#FF6A00;font-size:10pt;margin-bottom:2px}
  .print-head,.dc-sec,.ph-row{-webkit-print-color-adjust:exact;print-color-adjust:exact}
  mjx-container{max-width:100%}
}
.dc-bh>span:last-child{min-width:0}
.dc-bai mjx-container[jax="SVG"]:not([display="true"]){display:inline-block;max-width:100%}
.dc-bai mjx-container[jax="SVG"]:not([display="true"])>svg{max-width:100%;height:auto}
/* Bỏ nét viền 0px của MathJax: khi in/xuất PDF nét này bị vẽ thành nét mảnh làm công thức trông như in đậm */
mjx-container svg g[stroke-width="0"],mjx-container svg [stroke-width="0"]{stroke:none!important}
@media print{mjx-container svg g,mjx-container svg use,mjx-container svg path{stroke:none!important}mjx-container svg rect{stroke:none!important}}
.dc-bai{overflow-x:hidden}
.md .mchain{display:flex;flex-wrap:wrap;justify-content:center;align-items:center;column-gap:.35em;row-gap:6px;margin:10px 0;line-height:1.4}
.md .mchain>mjx-container{margin:0!important}
.dc-kt{overflow-x:hidden}
.dc-bai,.dc-bai .ex-top,.dc-bai .ex-sol,.dc-bai .md{min-width:0;max-width:100%}
.dc-bai .tbl{max-width:100%}
.dc-bai .tbl table{font-size:13.5px}.dc-bai .tbl th,.dc-bai .tbl td{padding:6px 8px;white-space:nowrap}
@media print{.dc-bai .tbl{overflow:visible}.dc-bai .tbl th,.dc-bai .tbl td{white-space:normal}}
.dc-img.wide img{max-width:min(100%,680px)}@media print{.dc-img.wide img{max-width:120mm!important}}
.md .cols.lg.c3,.md .cols.lg.c4{grid-template-columns:repeat(2,minmax(0,1fr))}
.md .cols.xl{grid-template-columns:1fr!important}
@media (max-width:700px){.md .cols.lg{grid-template-columns:1fr!important}}
.md .cols>div{white-space:normal}.md .cols>div mjx-container{white-space:nowrap}
.md .mchain>mjx-container{max-width:100%}.md .mchain>mjx-container>svg{max-width:100%;height:auto}
@media (max-width:900px){
  .hero{grid-template-columns:1fr}
  .tools{grid-template-columns:repeat(2,1fr)}
  .book{grid-template-columns:1fr}
  .toc{display:none}
  .toc-select{display:block}
  .cards{grid-template-columns:1fr}
}
@media (max-width:640px){
  .track-tiles{grid-template-columns:1fr}
  
  .top-row{gap:10px}
  
  .search input{height:42px}
  .tile{min-height:200px}
}

@media (prefers-reduced-motion:reduce){*{transition:none!important;animation:none!important}}

/* Trang tĩnh */
.crumbs{display:flex;flex-wrap:wrap;gap:6px;align-items:center;font-size:13.5px;color:var(--muted);margin-bottom:14px}
.crumbs a{color:var(--muted);text-decoration:none}.crumbs a:hover{color:var(--orange)}
.crumbs span.sep{opacity:.5}
a.res-item{text-decoration:none;color:inherit;display:block}
.toc a{display:flex;gap:10px;width:100%;text-align:left;padding:8px 10px;border-radius:12px;font-size:14.5px;line-height:1.35;align-items:flex-start;text-decoration:none;color:var(--ink)}
.toc a .n{font-family:var(--f-display);font-weight:700;font-size:13px;min-width:30px;color:var(--muted);padding-top:1px}
.toc a:hover{background:var(--surface-2)}
.or-t .toc a.on{background:var(--orange-tint);color:var(--orange);font-weight:600}.bl-t .toc a.on{background:var(--blue-tint);color:var(--blue-2);font-weight:600}.yl-t .toc a.on{background:var(--amber-tint);color:var(--amber-ink);font-weight:600}
.topic-list{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px;margin-bottom:26px}
.topic-list a{display:flex;gap:12px;align-items:flex-start;background:var(--surface);border:1px solid var(--line);border-radius:16px;padding:14px 16px;text-decoration:none;color:var(--ink)}
.topic-list a:hover{border-color:var(--orange)}
.topic-list .n{font-family:var(--f-display);font-weight:800;font-size:15px;min-width:38px;color:var(--muted)}
.topic-list b{display:block;font-weight:600}.topic-list small{color:var(--muted)}
.part-h{font-size:13px;font-weight:700;letter-spacing:.08em;text-transform:uppercase;color:var(--muted);margin:18px 0 10px}
.prose{max-width:760px;background:var(--surface);border:1px solid var(--line);border-radius:var(--r);padding:24px 26px}
.prose h2{font-size:20px;margin:18px 0 8px}.prose p,.prose li{color:var(--ink)}.prose a{color:var(--blue-2)}
.cta-app{display:flex;gap:12px;flex-wrap:wrap;align-items:center;justify-content:space-between;background:var(--surface);border:1px dashed var(--line);border-radius:16px;padding:14px 16px;margin-top:20px}
.sitemap-links{columns:3 220px;font-size:13.5px;margin:10px 0 0}.sitemap-links a{color:var(--muted);text-decoration:none;display:block;padding:2px 0}.sitemap-links a:hover{color:var(--orange)}
details.sol>summary{cursor:pointer;list-style:none;display:inline-flex}details.sol>summary::-webkit-details-marker{display:none}
details.sol[open]>summary .lbl-open{display:none}details.sol:not([open])>summary .lbl-close{display:none}
@media (max-width:700px){.topic-list{grid-template-columns:1fr}.prose{padding:18px}}