:root{
  --bg:#f3f6ff;--card:#fff;--ink:#1d2340;--muted:#6b7394;--line:#e4e8f6;
  --pri:#5b5ff5;--pri2:#8b5cf6;--pri-soft:#eceeff;
  --blue:#3b82f6;--green:#16b364;--orange:#f97316;--purple:#8b5cf6;--yellow:#eab308;--pink:#ec4899;--teal:#14b8a6;
  --ok:#16a34a;--okbg:#e6f9ee;--bad:#e5484d;--badbg:#ffecec;--warn:#b7791f;--warnbg:#fff4d6;
  --radius:18px;--shadow:0 2px 0 rgba(91,95,245,.06),0 8px 24px rgba(52,60,140,.08);
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
html{font-size:clamp(16px,.55vw + 10px,19px)}
body{margin:0;background:var(--bg);color:var(--ink);font:1rem/1.55 "Segoe UI",system-ui,-apple-system,Roboto,"Noto Sans",Arial,sans-serif}
a{color:var(--pri)}
h1{font-size:1.6rem;margin:.2em 0 .5em;font-weight:800}
h2{font-size:1.25rem;margin:1.2em 0 .5em;font-weight:800}
h3{font-size:1.05rem;margin:1em 0 .4em;font-weight:700}
.muted{color:var(--muted)}.small{font-size:.88rem}

/* ---------- khung trang ---------- */
#top{position:sticky;top:0;z-index:20;display:flex;gap:14px;align-items:center;flex-wrap:wrap;padding:10px 18px;
  background:linear-gradient(100deg,#5b5ff5 0%,#8b5cf6 55%,#ec4899 130%);color:#fff;box-shadow:0 4px 18px rgba(91,95,245,.35)}
#top .brand{font-weight:800;font-size:1.2rem;color:#fff;text-decoration:none;letter-spacing:.2px;white-space:nowrap}
#top .grades{display:flex;gap:6px;flex:1;flex-wrap:wrap}
#top .gr{padding:7px 16px;border-radius:999px;background:rgba(255,255,255,.18);color:#fff;text-decoration:none;font-weight:700;white-space:nowrap}
#top .gr:hover{background:rgba(255,255,255,.3)}
#top .gr.on{background:#fff;color:var(--pri);box-shadow:0 4px 12px rgba(0,0,0,.15)}
#top .gr.off{opacity:.45;cursor:default}
#top .gr.off:hover{background:rgba(255,255,255,.18)}
#top .userbox{display:flex;gap:8px;align-items:center;flex-wrap:wrap}
#top .who{font-weight:600}
#top .tbtn{background:rgba(255,255,255,.2);color:#fff;border:0;border-radius:999px;padding:6px 14px;font:inherit;font-size:.9rem;cursor:pointer;text-decoration:none}
#top .tbtn:hover{background:rgba(255,255,255,.35)}
.warnbar{flex-basis:100%;background:#fff4d6;color:#8a5a00;border-radius:10px;padding:6px 12px;font-size:.9rem}
#body{display:grid;grid-template-columns:230px minmax(0,1fr);min-height:calc(100vh - 62px)}
body.nosidebar #body{grid-template-columns:minmax(0,1fr)}
body.nosidebar #side{display:none}
#side{padding:18px 12px;background:#fff;border-right:1px solid var(--line)}
#side .side-title{font-size:.78rem;text-transform:uppercase;letter-spacing:.08em;color:var(--muted);font-weight:800;margin:4px 10px 10px}
#side a.item{display:flex;align-items:center;gap:10px;padding:11px 14px;margin:4px 0;border-radius:14px;color:var(--ink);text-decoration:none;font-weight:700}
#side a.item .ico{display:inline-grid;place-items:center;width:34px;height:34px;border-radius:11px;background:var(--pri-soft);font-size:1.1rem}
#side a.item:hover{background:var(--pri-soft)}
#side a.item.on{background:linear-gradient(100deg,var(--pri),var(--pri2));color:#fff;box-shadow:0 6px 16px rgba(91,95,245,.35)}
#side a.item.on .ico{background:rgba(255,255,255,.25)}
#side .hint{margin:14px 10px;color:var(--muted);font-size:.85rem}
main{padding:22px clamp(14px,3vw,40px) 90px;max-width:1180px;width:100%;margin:0 auto}
@media (max-width:820px){
  #body{grid-template-columns:1fr}
  #side{display:flex;gap:8px;overflow-x:auto;padding:10px 12px;border-right:0;border-bottom:1px solid var(--line);position:sticky;top:112px;z-index:15}
  #side .side-title,#side .hint{display:none}
  #side a.item{margin:0;white-space:nowrap;padding:8px 12px}
  #side a.item .ico{width:28px;height:28px}
  #top{padding:8px 12px}
}

/* ---------- thành phần chung ---------- */
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:16px 18px;margin:0 0 14px;box-shadow:var(--shadow)}
.grid{display:grid;gap:14px;grid-template-columns:repeat(auto-fill,minmax(250px,1fr))}
.row{display:flex;gap:10px;flex-wrap:wrap;align-items:center}
.spread{display:flex;justify-content:space-between;gap:10px;align-items:center;flex-wrap:wrap}
button,.btn{font:inherit;font-weight:700;border:0;border-radius:14px;padding:11px 20px;background:linear-gradient(100deg,var(--pri),var(--pri2));color:#fff;cursor:pointer;text-decoration:none;display:inline-block;box-shadow:0 5px 14px rgba(91,95,245,.3);transition:transform .08s}
button:hover,.btn:hover{transform:translateY(-1px)}
button:active,.btn:active{transform:translateY(1px)}
button.ghost,.btn.ghost{background:#fff;color:var(--pri);border:2px solid var(--pri-soft);box-shadow:none}
button.ghost:hover{background:var(--pri-soft)}
button.good{background:linear-gradient(100deg,#16b364,#14b8a6);box-shadow:0 5px 14px rgba(22,179,100,.3)}
button.bad{background:var(--bad);box-shadow:none}
button:disabled{opacity:.5;cursor:not-allowed;transform:none}
input[type=text],input[type=password],input[type=number],textarea,select{font:inherit;width:100%;padding:11px 13px;border:2px solid var(--line);border-radius:14px;background:#fff;color:var(--ink)}
input:focus,textarea:focus,select:focus{outline:0;border-color:var(--pri)}
textarea{min-height:120px;resize:vertical;line-height:1.55}
label{display:block;margin:10px 0 4px;font-weight:700}
.chip{display:inline-block;padding:3px 11px;border-radius:999px;font-size:.82rem;font-weight:700;background:var(--pri-soft);color:var(--pri);margin:0 6px 0 0}
.chip.ok{background:var(--okbg);color:var(--ok)}.chip.bad{background:var(--badbg);color:var(--bad)}.chip.warn{background:var(--warnbg);color:var(--warn)}
.bar{height:10px;border-radius:99px;background:#e8ebf8;overflow:hidden}.bar>i{display:block;height:100%;border-radius:99px;background:linear-gradient(90deg,var(--pri),var(--pri2))}
.bar.ok>i{background:linear-gradient(90deg,#16b364,#14b8a6)}.bar.warn>i{background:linear-gradient(90deg,#f59e0b,#f97316)}.bar.bad>i{background:linear-gradient(90deg,#f43f5e,#e5484d)}
.err{background:var(--badbg);color:var(--bad);border-radius:14px;padding:10px 14px;margin:10px 0;font-weight:600}
.okmsg{background:var(--okbg);color:var(--ok);border-radius:14px;padding:10px 14px;margin:10px 0;font-weight:600}
.advice{background:var(--warnbg);border-left:5px solid #f59e0b;border-radius:14px;padding:10px 14px;margin:10px 0}
table{border-collapse:collapse;width:100%}th,td{text-align:left;padding:9px 10px;border-bottom:1px solid var(--line);vertical-align:top}
ul.tight{margin:4px 0;padding-left:22px}
details{margin:6px 0}summary{cursor:pointer;font-weight:700}
.crumbs{font-size:.9rem;color:var(--muted);margin-bottom:6px}.crumbs a{text-decoration:none;font-weight:600}

/* ---------- học sinh: trang môn học ---------- */
.hello{background:linear-gradient(110deg,#fff7e0,#ffe8f1 60%,#e7edff);border-radius:24px;padding:20px 24px;margin-bottom:18px;display:flex;justify-content:space-between;gap:16px;align-items:center;flex-wrap:wrap}
.hello h1{margin:0}.hello .big{font-size:2.4rem}
.chapter{margin:22px 0 10px;display:flex;gap:10px;align-items:baseline;flex-wrap:wrap}
.chapter .no{background:linear-gradient(100deg,var(--orange),var(--pink));color:#fff;border-radius:12px;padding:3px 12px;font-weight:800}
.chapter h2{margin:0}
.tile{display:block;text-decoration:none;color:inherit;background:#fff;border:1px solid var(--line);border-radius:20px;padding:16px;box-shadow:var(--shadow);position:relative;overflow:hidden;transition:transform .12s}
.tile:before{content:"";position:absolute;left:0;top:0;right:0;height:6px;background:linear-gradient(90deg,var(--blue),var(--purple))}
.tile:hover{transform:translateY(-3px)}
.tile .no{font-size:.8rem;font-weight:800;color:var(--pri);text-transform:uppercase;letter-spacing:.05em;margin-top:4px}
.tile .tt{font-size:1.15rem;font-weight:800;margin:2px 0 10px}
.badge-star{background:var(--warnbg);color:var(--warn);border-radius:999px;padding:2px 10px;font-weight:800;font-size:.85rem}

/* ---------- học sinh: trang bài học ---------- */
.hero{border-radius:24px;padding:18px 22px;color:#fff;background:linear-gradient(110deg,#3b82f6,#8b5cf6 60%,#ec4899);display:flex;justify-content:space-between;gap:16px;align-items:center;flex-wrap:wrap;box-shadow:0 10px 26px rgba(91,95,245,.3)}
.hero .sub{opacity:.9;font-weight:600}.hero h1{margin:.1em 0;color:#fff}
.ring{--p:0;width:78px;height:78px;border-radius:50%;display:grid;place-items:center;font-weight:800;background:conic-gradient(#fff calc(var(--p)*1%),rgba(255,255,255,.3) 0);position:relative}
.ring:after{content:"";position:absolute;inset:8px;border-radius:50%;background:#7a5cf0}
.ring span{position:relative;z-index:1;font-size:.95rem}
.tabs{display:flex;gap:8px;flex-wrap:wrap;margin:16px 0}
.tabs a{--c:var(--pri);padding:9px 16px;border-radius:999px;background:#fff;border:2px solid var(--line);text-decoration:none;color:var(--ink);font-weight:700;white-space:nowrap}
.tabs a:hover{border-color:var(--c)}
.tabs a.on{background:var(--c);border-color:var(--c);color:#fff;box-shadow:0 6px 14px color-mix(in srgb,var(--c) 40%,transparent)}
.t-kien{--c:var(--blue)}.t-cb{--c:var(--green)}.t-nc{--c:var(--orange)}.t-thi{--c:var(--purple)}.t-tk{--c:#d9a000}
.kcard{border-left:6px solid var(--blue)}
.kcard h3{margin-top:0}
.skill{display:flex;gap:10px;align-items:flex-start;padding:6px 0}.skill:before{content:"✔";color:#fff;background:var(--green);border-radius:50%;width:22px;height:22px;display:grid;place-items:center;font-size:.75rem;flex:none;margin-top:3px}
.dang{border-top:6px solid var(--green)}
.dang.nc{border-top-color:var(--orange)}
.dang h3{margin:0}
.twocol{display:grid;gap:12px;grid-template-columns:1fr 1fr;margin-top:10px}
@media (max-width:640px){.twocol{grid-template-columns:1fr}}
.box{border-radius:16px;padding:12px 14px}
.box h4{margin:0 0 6px}.box.nb{background:#e8f1ff}.box.cl{background:#e6f9ee}.box.bt{background:#fff1e3;margin-top:12px}
.box ol,.box ul{margin:4px 0;padding-left:20px}
.qrow{display:flex;gap:12px;align-items:center;padding:10px 14px;border:2px solid var(--line);border-radius:16px;margin:8px 0;text-decoration:none;color:inherit;background:#fff}
.qrow:hover{border-color:var(--pri);background:var(--pri-soft)}
.qrow .t{flex:1;min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.st{width:34px;height:34px;border-radius:50%;display:grid;place-items:center;font-size:1rem;flex:none;background:#eef0fa}
.st.right{background:var(--okbg)}.st.wrong{background:var(--badbg)}.st.partial{background:var(--warnbg)}.st.pending{background:var(--pri-soft)}
.tkcard{border-left:6px solid var(--yellow)}
.mistake{background:#fff4d6;border-radius:16px;padding:12px 14px;margin:10px 0;border-left:6px solid #f59e0b}

/* ---------- làm bài / kết quả ---------- */
.qbox{background:#fff;border:1px solid var(--line);border-radius:20px;padding:18px 20px;margin:12px 0;box-shadow:var(--shadow);font-size:1.08rem}
.symbols{display:flex;gap:6px;flex-wrap:wrap;margin:8px 0}
.symbols button{padding:5px 11px;background:#fff;color:var(--ink);border:2px solid var(--line);box-shadow:none;font-size:1.05rem;min-width:40px;border-radius:12px}
.symbols button:hover{background:var(--pri-soft);border-color:var(--pri)}
.sol{background:#eef3ff;border-radius:16px;padding:12px 14px;margin:10px 0}
.sol .final{font-weight:800;color:var(--ok)}
.sol ol{margin:6px 0 0;padding-left:22px}
.mine{background:#fff;border:2px dashed var(--line);border-radius:14px;padding:10px 12px;white-space:pre-wrap;margin:6px 0}
.opt{display:flex;gap:10px;align-items:flex-start;padding:11px 14px;border:2px solid var(--line);border-radius:16px;margin:8px 0;cursor:pointer;background:#fff}
.opt input{margin-top:6px}.opt.picked{border-color:var(--pri);background:var(--pri-soft)}
.opt.right{border-color:var(--ok);background:var(--okbg)}.opt.wrong{border-color:var(--bad);background:var(--badbg)}
.timer{position:sticky;top:70px;z-index:4;background:#fff;border:2px solid var(--pri-soft);border-radius:18px;padding:8px 16px;margin-bottom:12px;display:flex;justify-content:space-between;align-items:center;gap:10px;box-shadow:var(--shadow)}
.timer b{font-size:1.4rem;font-variant-numeric:tabular-nums;color:var(--pri)}.timer.low b{color:var(--bad)}
.qnum{font-weight:800;color:var(--pri)}
.figure{border:2px dashed var(--line);border-radius:14px;padding:8px 12px;margin:8px 0;color:var(--muted)}
.figure img{max-width:100%;display:block;margin:6px auto}
.grade{display:inline-flex;gap:6px}
.grade button{background:#fff;color:var(--ink);border:2px solid var(--line);box-shadow:none}
.grade button.sel-ok{background:var(--ok);color:#fff;border-color:var(--ok)}
.grade button.sel-bad{background:var(--bad);color:#fff;border-color:var(--bad)}
.score{font-size:2.4rem;font-weight:800;background:linear-gradient(100deg,var(--pri),var(--pink));-webkit-background-clip:text;background-clip:text;color:transparent}

/* ---------- phụ huynh / quản trị ---------- */
.pagehead{display:flex;justify-content:space-between;align-items:center;gap:12px;flex-wrap:wrap;margin-bottom:10px}
.pagehead h1{margin:0}
.seg{display:inline-flex;background:#e9ecfb;border-radius:999px;padding:4px;gap:4px;margin:8px 0 14px}
.seg a,.seg button{border:0;background:transparent;color:var(--ink);box-shadow:none;border-radius:999px;padding:8px 18px;text-decoration:none;font-weight:700}
.seg a.on{background:#fff;color:var(--pri);box-shadow:0 2px 8px rgba(0,0,0,.1)}
.group{margin:20px 0 8px;display:flex;gap:10px;align-items:baseline;flex-wrap:wrap}
.group .lb{font-weight:800;font-size:1.1rem}.group .nm{color:var(--muted)}
.trow{display:flex;gap:14px;align-items:center;justify-content:space-between;flex-wrap:wrap;padding:12px 14px;border:2px solid var(--line);border-radius:16px;margin:8px 0;background:#fff}
.trow .main{flex:1;min-width:220px}
.trow .big{font-size:1.4rem;font-weight:800;color:var(--pri)}
.att{border:2px solid var(--line);border-radius:16px;margin:8px 0;background:#fff;padding:2px 14px}
.att>summary{padding:10px 0;display:flex;gap:10px;align-items:center;flex-wrap:wrap;list-style:none}
.att>summary::-webkit-details-marker{display:none}
.att[open]{border-color:var(--pri)}
.statgrid{display:grid;gap:12px;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));margin:10px 0 16px}
.stat{background:#fff;border:1px solid var(--line);border-radius:18px;padding:12px 16px;box-shadow:var(--shadow)}
.stat b{display:block;font-size:1.6rem;color:var(--pri)}
@media print{#top,#side,.symbols,button{display:none!important}#body{display:block}}

/* ---------- đăng nhập: căn giữa theo mọi cỡ màn hình ---------- */
.card.login{max-width:420px;margin:clamp(24px,10vh,110px) auto 0;padding:26px 28px;text-align:left}
.card.login .brandmark{font-size:2.4rem}

/* ---- luyện tập: đề + bài làm ở trái, khung "nhận biết và cách làm" ở phải (màn hình rộng) hoặc thu gọn phía trên (màn hình hẹp) ---- */
.qlayout{display:grid;grid-template-columns:minmax(0,1.5fr) minmax(0,1fr);grid-template-areas:"main hint";gap:20px;align-items:start}
.qmain{grid-area:main;min-width:0}
.hintpanel{grid-area:hint;position:sticky;top:12px;max-height:calc(100vh - 24px);overflow:auto;background:#fff;border:1px solid var(--line);border-radius:20px;padding:14px 16px;box-shadow:var(--shadow)}
.hintpanel>summary{font-weight:800;font-size:1.05rem;cursor:pointer;list-style:none}
.hintpanel>summary::-webkit-details-marker{display:none}
.hintpanel>summary::after{content:" ▾";color:var(--muted)}
.hintpanel:not([open])>summary::after{content:" ▸"}
.hintpanel[open]>summary{margin-bottom:8px}
.hintpanel .twocol{grid-template-columns:1fr}
@media (min-width:1100px){.hintpanel>summary{pointer-events:none;cursor:default}.hintpanel>summary::after,.hintpanel:not([open])>summary::after{content:""}}
@media (max-width:1099px){.qlayout{grid-template-columns:minmax(0,1fr);grid-template-areas:"hint" "main"}.hintpanel{position:static;max-height:none}}
textarea.work{min-height:240px}
/* cụm nút sau khi nộp bài: hàng chính (lưu, tiếp theo) và hàng phụ (làm lại, báo sai) */
.actions{margin:14px 0}
.act-main,.act-sub{display:flex;flex-wrap:wrap;gap:10px}
.act-sub{margin-top:10px}
.act-main>*{flex:1 1 230px;display:flex;align-items:center;justify-content:center;text-align:center;white-space:normal;line-height:1.35}

/* ---- hộp thoại nhắc nhở, nút đã lưu, huy hiệu số câu cần ôn ---- */
.modal-bg{position:fixed;inset:0;background:rgba(30,27,75,.45);display:flex;align-items:center;justify-content:center;padding:16px;z-index:50}
.modal{background:#fff;border-radius:22px;padding:20px 22px;max-width:460px;width:100%;box-shadow:0 20px 50px rgba(0,0,0,.25)}
button.saved,button.saved:disabled{background:var(--okbg);color:var(--ok);box-shadow:none;opacity:1;cursor:default}
.nbadge{margin-left:auto;background:var(--bad);color:#fff;border-radius:999px;font-size:.78rem;font-weight:800;padding:1px 8px}
.cardmsg{margin-top:8px}

/* ---- nhãn môn, chúc mừng, confetti, icon dạng ---- */
.mon{color:var(--ok);font-weight:800}
#side a.item.on .mon{color:#bbf7d0}
.dst{display:inline-block;min-width:1.3em}
.confetti-box{position:fixed;inset:0;pointer-events:none;overflow:hidden;z-index:70}
.confetti-box i{position:absolute;top:-16px;width:9px;height:14px;border-radius:2px;animation-name:confetti-fall;animation-timing-function:linear;animation-fill-mode:forwards}
@keyframes confetti-fall{0%{transform:translateY(0) rotate(0)}100%{transform:translateY(108vh) rotate(720deg)}}
.cel-bg{position:fixed;inset:0;background:rgba(30,27,75,.5);display:flex;align-items:center;justify-content:center;padding:16px;z-index:60}
.cel{background:#fff;border-radius:26px;padding:24px 26px;max-width:440px;width:100%;text-align:center;box-shadow:0 24px 60px rgba(0,0,0,.3);animation:cel-pop .35s ease-out}
.cel h2{margin:.2em 0 .6em}.cel-ico{font-size:3.2rem}.cel-line{background:var(--okbg);border-radius:14px;padding:8px 12px;margin:8px 0}
.cel-ok{margin-top:10px}
@keyframes cel-pop{0%{transform:scale(.7);opacity:0}100%{transform:scale(1);opacity:1}}
.cel-toast{position:fixed;right:18px;bottom:18px;display:flex;gap:10px;align-items:center;background:#fff;border:2px solid var(--ok);border-radius:18px;padding:10px 16px;z-index:60;box-shadow:0 12px 30px rgba(0,0,0,.2);max-width:340px;animation:cel-pop .3s ease-out}
.cel-toast>span{font-size:1.8rem}
@media (prefers-reduced-motion: reduce){.confetti-box{display:none}.cel,.cel-toast{animation:none}}

/* ---- công cụ đặt tính; khung bài làm dùng chữ đơn cách để các khối đặt tính căn thẳng cột ---- */
textarea.work,.mine{font-family:"Cascadia Mono",Consolas,"Courier New",ui-monospace,monospace;font-size:.98rem}
.dtpanel{background:#fff;border:2px solid var(--pri-soft);border-radius:18px;padding:12px 14px;margin:8px 0}
.dtkinds{display:flex;gap:8px;flex-wrap:wrap}
.dtk{background:#fff;color:var(--ink);border:2px solid var(--line);box-shadow:none;padding:7px 13px}
.dtk.on{background:var(--pri-soft);border-color:var(--pri)}
.dtform{display:flex;gap:10px;flex-wrap:wrap;align-items:flex-end;margin:10px 0 4px}
.dtform label{display:block;font-size:.85rem;color:var(--muted);margin-bottom:2px}
.dtform input{width:150px;min-height:0}
.dtgrid{font-family:"Cascadia Mono",Consolas,"Courier New",ui-monospace,monospace;background:#fbfbff;border:1px dashed var(--line);border-radius:14px;padding:10px 12px;margin:8px 0;max-width:100%;overflow-x:auto}
.dtinner{display:inline-block;min-width:0}
.dtrow{display:flex;align-items:center}
.dtL,.dtR{display:flex}
.dtR{--n:1;min-width:calc(var(--n) * (1.8em + 2px));min-height:1.9em;align-self:flex-start}
.dtR.top{border-bottom:2px solid var(--ink)}
.dtbar{width:2px;align-self:stretch;background:var(--ink);margin:0 6px}
.dtc{width:1.8em;height:1.9em;margin:1px;padding:0;text-align:center;font:inherit;font-size:1.05rem;border:1px solid var(--line);border-radius:7px;background:#fff;box-sizing:border-box;min-height:0}
.dtc:focus{border-color:var(--pri);outline:2px solid var(--pri-soft)}
.dtc.g{background:#eef2ff;border-color:#c7d2fe;font-weight:700;color:#1e1b4b}
.dtc.f{display:inline-flex;align-items:center;justify-content:center;border:none;background:none;font-weight:800;color:var(--pri)}
.dtc.s{border:none;background:none}
.dtc.e.carry{height:1.35em;font-size:.82rem;border-style:dotted;color:#b45309;background:#fffbeb}
.dtc.w{width:5.4em}
.dtline{display:block;height:0;border-top:2px solid var(--ink);margin:3px 0}
.dthdr{font-size:.85rem;color:var(--muted);margin-bottom:4px;font-family:inherit}
@media print{.dtpanel{display:none!important}}