:root{
  --paper:#f3f6fb; --grid:rgba(35,71,230,.07); --ink:#0f1f3d; --muted:#4a5a78; --card:#ffffff; --line:#cfd8e8;
  --blue:#2347e6; --on-blue:#ffffff; --amber:#ffb000; --ok:#0b7a54; --bad:#c2301d; --soft:#e8eefb;
  box-sizing:border-box;
  padding-top:env(safe-area-inset-top,0px);
  padding-bottom:env(safe-area-inset-bottom,0px);
}
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){
    --paper:#0b1426; --grid:rgba(120,160,255,.08); --ink:#e6edfb; --muted:#9fb0d0; --card:#121e36; --line:#243553;
    --blue:#8aa2ff; --on-blue:#0a1330; --amber:#ffc533; --ok:#4fd1a0; --bad:#ff8a78; --soft:#182744;
  }
}
:root[data-theme="dark"]{
  --paper:#0b1426; --grid:rgba(120,160,255,.08); --ink:#e6edfb; --muted:#9fb0d0; --card:#121e36; --line:#243553;
  --blue:#8aa2ff; --on-blue:#0a1330; --amber:#ffc533; --ok:#4fd1a0; --bad:#ff8a78; --soft:#182744;
}
*,*::before,*::after{box-sizing:inherit}
html{scroll-padding-top:env(safe-area-inset-top,0px)}
[hidden]{display:none!important}
body{
  margin:0;color:var(--ink);background-color:var(--paper);
  background-image:linear-gradient(var(--grid) 1px,transparent 1px),linear-gradient(90deg,var(--grid) 1px,transparent 1px);
  background-size:24px 24px;
  font:400 16px/1.65 "Hind Siliguri","Noto Sans Bengali",system-ui,sans-serif;
  -webkit-text-size-adjust:100%;
}
button,input,select,textarea{font:inherit;color:inherit}
button{cursor:pointer}
:focus-visible{outline:3px solid var(--blue);outline-offset:2px}
h1,h2,h3{font-family:"Anek Bangla","Hind Siliguri",sans-serif;line-height:1.25;margin:0}
p{margin:0}
.wrap{max-width:1040px;margin:0 auto;padding:0 16px}

/* Header */
.top{padding:14px 0 0}
.brand{display:flex;align-items:center;gap:10px}
.brand svg{flex:none}
.brand b{font:800 22px/1 "Anek Bangla",sans-serif}
.brand span{display:block;font-size:13px;color:var(--muted);margin-top:2px}
.nav{display:flex;gap:6px;overflow-x:auto;padding:12px 0 10px;scrollbar-width:none;position:sticky;top:0;z-index:5;
  background:linear-gradient(var(--paper) 78%,transparent)}
.nav::-webkit-scrollbar{display:none}
.nav button{
  flex:none;border:1px solid var(--line);background:var(--card);border-radius:999px;padding:8px 16px;min-height:44px;font-weight:600
}
.nav button[aria-current="page"]{background:var(--blue);color:var(--on-blue);border-color:transparent}

main{padding:8px 0 56px;min-height:60vh}
.sec-title{font-size:22px;margin:22px 0 10px}
.lead{color:var(--muted);max-width:60ch}

/* Hero */
.hero{display:grid;gap:18px;margin-top:8px}
@media(min-width:820px){.hero{grid-template-columns:1fr 1.05fr;align-items:center;margin-top:24px}}
.hero h1{font-size:clamp(34px,7vw,52px);font-weight:800;letter-spacing:-.5px}
.hero .lead{margin-top:10px;font-size:17px}
.bench{background:var(--card);border:1px solid var(--line);border-radius:20px 20px 20px 4px;padding:14px}
.bench .hint{font-size:14px;color:var(--muted);margin-bottom:6px}
.rsvg{width:100%;height:auto;display:block}
.band{cursor:pointer}
.band:focus-visible{outline:3px solid var(--blue);outline-offset:2px}
.rout{font:800 28px/1.2 "Anek Bangla",sans-serif;margin:6px 0 10px}
.rout small{font:500 15px "Hind Siliguri";color:var(--muted);margin-left:6px}
.sel4{display:grid;grid-template-columns:1fr 1fr;gap:8px}
.sel4 label{font-size:13px;color:var(--muted);display:grid;gap:3px}
select,input[type=text],input[type=number],input[type=search],textarea{
  width:100%;border:1px solid var(--line);background:var(--paper);border-radius:8px;padding:9px 10px;min-height:44px
}
textarea{line-height:1.5;resize:vertical}

/* Cards */
.grid4{display:grid;gap:10px;grid-template-columns:1fr 1fr;margin-top:22px}
@media(min-width:820px){.grid4{grid-template-columns:repeat(4,1fr)}}
.feat{
  text-align:left;border:1px solid var(--line);background:var(--card);border-radius:14px;padding:14px;display:grid;gap:4px;
}
.feat:nth-child(2){border-radius:14px 14px 4px 14px}
.feat:nth-child(3){border-radius:4px 14px 14px 14px}
.feat h3{font-size:18px}
.feat p{font-size:14px;color:var(--muted)}
.feat .n{font:800 28px/1 "Anek Bangla",sans-serif;color:var(--blue)}

.chips{display:flex;gap:6px;flex-wrap:wrap;margin:10px 0}
.chip{border:1px solid var(--line);background:var(--card);border-radius:999px;padding:6px 14px;min-height:40px;font-weight:600}
.chip[aria-pressed="true"]{background:var(--ink);color:var(--paper);border-color:transparent}
.tag{display:inline-block;font-size:13px;font-weight:600;color:var(--blue);background:var(--soft);border-radius:6px;padding:1px 8px}

.cgrid{display:grid;gap:12px;grid-template-columns:repeat(auto-fill,minmax(210px,1fr))}
.ccard{
  text-align:left;border:1px solid var(--line);background:var(--card);border-radius:14px;overflow:hidden;padding:0;display:grid
}
.cart{background:var(--soft);display:grid;place-items:center;aspect-ratio:16/10;overflow:hidden;
  background-image:radial-gradient(var(--line) 1px,transparent 1px);background-size:12px 12px}
.cart svg,.cart img{width:100%;height:100%;object-fit:contain}
.cart img{object-fit:cover}
.cbody{padding:10px 12px 12px;display:grid;gap:3px}
.cbody h3{font-size:17px}
.cbody p{font-size:14px;color:var(--muted)}

/* Dialog */
dialog{
  border:1px solid var(--line);border-radius:18px;background:var(--card);color:var(--ink);
  max-width:680px;width:calc(100% - 20px);max-height:92vh;padding:0;overflow:auto
}
dialog::backdrop{background:rgba(5,10,25,.6)}
.dhead{display:flex;justify-content:space-between;align-items:flex-start;gap:10px;padding:16px 16px 0}
.dhead h2{font-size:24px}
.dbody{padding:12px 16px 20px}
.dart{background:var(--soft);border-radius:12px;aspect-ratio:16/9;display:grid;place-items:center;overflow:hidden;margin-bottom:10px;
  background-image:radial-gradient(var(--line) 1px,transparent 1px);background-size:12px 12px}
.dart svg{width:100%;height:100%}
.dart img{width:100%;height:100%;object-fit:contain;background:#000}
.btn{border:1px solid var(--line);background:var(--card);border-radius:10px;padding:8px 16px;min-height:44px;font-weight:600}
.btn.pri{background:var(--blue);color:var(--on-blue);border-color:transparent}
.btn.bad{background:var(--bad);color:#fff;border-color:transparent}
.btn.sm{min-height:36px;padding:4px 12px;font-size:14px}
.btn:disabled{opacity:.45;cursor:not-allowed}
.row{display:flex;gap:8px;flex-wrap:wrap;align-items:center}
.seg2{display:inline-flex;border:1px solid var(--line);border-radius:10px;overflow:hidden;margin-bottom:10px}
.seg2 button{border:0;background:transparent;padding:8px 14px;min-height:40px;font-weight:600}
.seg2 button[aria-pressed="true"]{background:var(--ink);color:var(--paper)}
table.spec{width:100%;border-collapse:collapse;margin:6px 0 12px;font-size:15px}
table.spec th,table.spec td{text-align:left;padding:7px 8px;border-bottom:1px solid var(--line);vertical-align:top}
table.spec th{width:38%;color:var(--muted);font-weight:600}
.dbody h3{font-size:17px;margin:14px 0 4px}
.dbody ul{margin:4px 0 0;padding-left:20px}

/* Topics */
.tlist{display:grid;gap:10px}
.titem{text-align:left;border:1px solid var(--line);background:var(--card);border-radius:14px;padding:14px;display:grid;gap:4px}
.titem h3{font-size:19px}
.titem .meta{font-size:13px;color:var(--muted)}
.article{background:var(--card);border:1px solid var(--line);border-radius:16px;padding:16px;margin-top:10px}
.article h2{font-size:26px;margin-bottom:6px}
.article h3{font-size:19px;margin:18px 0 4px}
.article p{margin:6px 0;max-width:68ch}
.article li{margin:3px 0}
.formula{
  font:italic 400 20px/1.5 "STIX Two Text","Times New Roman",serif;background:var(--soft);border-left:4px solid var(--amber);
  padding:8px 14px;margin:8px 0;border-radius:0 8px 8px 0;overflow-x:auto
}

/* Tools */
.tools{display:grid;gap:14px}
@media(min-width:820px){.tools{grid-template-columns:1fr 1fr}.tools .wide{grid-column:1/-1}}
.tool{background:var(--card);border:1px solid var(--line);border-radius:16px;padding:14px}
.tool h3{font-size:19px;margin-bottom:2px}
.tool .sub{font-size:14px;color:var(--muted);margin-bottom:10px}
.fields{display:grid;gap:8px;grid-template-columns:repeat(auto-fit,minmax(110px,1fr))}
.fields label{display:grid;gap:3px;font-size:13px;color:var(--muted)}
.result{margin-top:10px;padding:10px 12px;background:var(--soft);border-radius:10px;font-weight:600;min-height:44px}
.result div{margin:2px 0}

/* Quiz */
.quiz{background:var(--card);border:1px solid var(--line);border-radius:16px;padding:16px;max-width:680px}
.qbar{height:8px;background:var(--soft);border-radius:99px;overflow:hidden;margin-bottom:12px}
.qbar i{display:block;height:100%;background:var(--blue)}
.qq{font:700 20px/1.4 "Anek Bangla","Hind Siliguri",sans-serif;margin-bottom:12px}
.opt{display:block;width:100%;text-align:left;border:1px solid var(--line);background:var(--paper);border-radius:10px;padding:10px 14px;margin:6px 0;min-height:48px}
.opt.right{border-color:var(--ok);box-shadow:0 0 0 2px var(--ok)}
.opt.wrong{border-color:var(--bad);box-shadow:0 0 0 2px var(--bad)}
.explain{margin:10px 0;padding:10px 12px;background:var(--soft);border-radius:10px}
.score{font:800 44px/1.1 "Anek Bangla",sans-serif;color:var(--blue)}

/* Account + admin */
.panel{background:var(--card);border:1px solid var(--line);border-radius:16px;padding:16px;margin-top:10px}
.panel h3{font-size:19px;margin-bottom:6px}
.note{font-size:14px;color:var(--muted)}
.admin{display:grid;gap:12px}
@media(min-width:820px){.admin{grid-template-columns:200px 1fr}}
.atabs{display:flex;gap:6px;flex-wrap:wrap}
@media(min-width:820px){.atabs{flex-direction:column;flex-wrap:nowrap}}
.atabs button{border:1px solid var(--line);background:var(--card);border-radius:10px;padding:10px 14px;text-align:left;min-height:44px;font-weight:600}
.atabs button[aria-current="true"]{background:var(--ink);color:var(--paper);border-color:transparent}
.arow{display:flex;gap:8px;align-items:center;justify-content:space-between;padding:10px 0;border-bottom:1px solid var(--line)}
.arow b{display:block}
.arow .note{display:block}
.form{display:grid;gap:12px}
.form label{display:grid;gap:4px;font-weight:600;font-size:14px}
.thumb{max-width:220px;border-radius:10px;border:1px solid var(--line);display:block;margin-bottom:6px}
.empty{padding:22px;border:1px dashed var(--line);border-radius:14px;color:var(--muted);text-align:center}
.toast{position:fixed;left:50%;transform:translateX(-50%);bottom:calc(16px + env(safe-area-inset-bottom,0px));
  background:var(--ink);color:var(--paper);padding:10px 16px;border-radius:10px;z-index:30;max-width:calc(100% - 32px)}
footer{border-top:1px solid var(--line);padding:18px 0 30px;color:var(--muted);font-size:14px}
@media (prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;transition:none!important}}

.auth input{display:block;width:100%;max-width:420px;padding:11px 12px;margin:8px 0;border:1px solid var(--line);border-radius:10px;background:var(--card)}
.auth .btn{margin:4px 6px 4px 0}