/* StudyNest – design tokens ------------------------------------------------- */
:root{
  --ink:#14213D; --ink-2:#44506B; --ink-3:#7A86A1;
  --paper:#F6F8FD; --card:#FFFFFF; --line:#DCE3F1; --line-2:#EAEFF9;
  --brand:#5B4BFF; --brand-ink:#FFFFFF; --brand-soft:#ECE9FF;
  --sun:#FFC93C; --sun-soft:#FFF4D1; --coral:#FF5C8A; --coral-soft:#FFE3EC;
  --mint:#12C79A; --mint-soft:#D9F8EE; --sky:#2BA8F5; --sky-soft:#DDF1FF;
  --err:#E5384F; --err-soft:#FFE4E8; --ok:#0FA37F;
  --code-bg:#101733; --code-ink:#E7ECFF; --code-dim:#7C88B3;
  --r-s:8px; --r-m:14px; --r-l:22px;
  --shadow:0 1px 0 rgba(20,33,61,.04),0 8px 24px -12px rgba(20,33,61,.18);
  --f-display:'Bricolage Grotesque','Hind Siliguri',system-ui,sans-serif;
  --f-body:'Hind Siliguri',system-ui,-apple-system,'Segoe UI',sans-serif;
  --f-mono:'JetBrains Mono',ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;
}
:root[data-theme=dark]{
  --ink:#EEF1FF; --ink-2:#B4BCDA; --ink-3:#7F8AAE;
  --paper:#0C1124; --card:#151B36; --line:#262E52; --line-2:#1D2444;
  --brand:#8E82FF; --brand-ink:#0C1124; --brand-soft:#242155;
  --sun-soft:#3A3115; --coral-soft:#3B1D2D; --mint-soft:#10332D; --sky-soft:#12304A;
  --err-soft:#3C1A22; --code-bg:#0A0E20;
  --shadow:0 1px 0 rgba(0,0,0,.3),0 10px 28px -14px rgba(0,0,0,.7);
}
*{box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}*{animation-duration:.001ms!important;transition-duration:.001ms!important}}
body{margin:0;background:var(--paper);color:var(--ink);font:400 17px/1.65 var(--f-body);position:relative;min-height:100vh}
h1,h2,h3,h4{font-family:var(--f-display);line-height:1.15;margin:0 0 .5em;letter-spacing:-.01em}
h1{font-size:clamp(2rem,5vw,3.4rem);font-weight:800}
h2{font-size:clamp(1.45rem,3vw,2rem);font-weight:700}
h3{font-size:1.2rem;font-weight:700}
p{margin:0 0 1em}
a{color:var(--brand);text-underline-offset:3px}
code,kbd,pre,.mono{font-family:var(--f-mono)}
:not(pre)>code{background:var(--brand-soft);color:var(--ink);padding:.08em .38em;border-radius:6px;font-size:.88em}
:focus-visible{outline:3px solid var(--sun);outline-offset:2px;border-radius:6px}
.skip{position:absolute;left:-999px;top:0;background:var(--sun);color:#14213D;padding:.6rem 1rem;z-index:99}
.skip:focus{left:8px;top:8px}
.wrap{max-width:1100px;margin:0 auto;padding:0 16px}
.narrow{max-width:760px}
.hide{display:none!important}
.muted{color:var(--ink-2)}
.sr{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0)}

/* Header ----------------------------------------------------------------- */
#top{position:sticky;top:0;z-index:30;background:color-mix(in srgb,var(--paper) 88%,transparent);backdrop-filter:blur(10px);border-bottom:1px solid var(--line)}
.bar{display:flex;align-items:center;gap:10px;height:62px}
.brand{display:flex;align-items:center;gap:10px;font:800 1.35rem var(--f-display);color:var(--ink);text-decoration:none}
.brand i{width:34px;height:34px;border-radius:10px;background:var(--brand);display:grid;place-items:center}
.brand svg{width:22px;height:22px}
.nav{display:flex;gap:2px;margin-left:14px}
.nav a{padding:8px 12px;border-radius:10px;color:var(--ink-2);text-decoration:none;font-weight:600;font-size:.95rem}
.nav a:hover,.nav a[aria-current]{background:var(--brand-soft);color:var(--ink)}
.sp{flex:1}
.tools{display:flex;gap:6px;align-items:center}
.ibtn{border:1px solid var(--line);background:var(--card);color:var(--ink);height:38px;min-width:38px;padding:0 10px;border-radius:10px;font:600 .9rem var(--f-body);cursor:pointer;display:inline-flex;align-items:center;justify-content:center;gap:6px}
.ibtn:hover{border-color:var(--brand)}
.burger{display:none}
@media (max-width:820px){
  .nav{position:fixed;inset:62px 0 auto 0;background:var(--paper);flex-direction:column;padding:10px 16px 16px;border-bottom:1px solid var(--line);display:none;margin:0}
  .nav.open{display:flex}.nav a{padding:12px}.burger{display:inline-flex}
  .tools .hide-m{display:none}
}

/* Buttons / forms --------------------------------------------------------- */
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;padding:11px 20px;border-radius:12px;border:2px solid var(--ink);background:var(--card);color:var(--ink);font:700 1rem var(--f-body);cursor:pointer;text-decoration:none;box-shadow:3px 3px 0 var(--ink);transition:transform .08s,box-shadow .08s}
.btn:hover{transform:translate(-1px,-1px);box-shadow:4px 4px 0 var(--ink)}
.btn:active{transform:translate(2px,2px);box-shadow:1px 1px 0 var(--ink)}
.btn.pri{background:var(--brand);color:var(--brand-ink)}
.btn.sun{background:var(--sun);color:#14213D;border-color:#14213D;box-shadow:3px 3px 0 #14213D}
.btn.mint{background:var(--mint);color:#06281F;border-color:#06281F;box-shadow:3px 3px 0 #06281F}
.btn.sm{padding:6px 12px;font-size:.9rem;border-radius:10px}
.btn[disabled]{opacity:.5;pointer-events:none}
.btn.ghost{box-shadow:none;border-color:var(--line);background:transparent}
:root[data-theme=dark] .btn{border-color:#8E82FF;box-shadow:3px 3px 0 #8E82FF}
:root[data-theme=dark] .btn.ghost{box-shadow:none;border-color:var(--line)}
label.f{display:block;font-weight:600;margin:0 0 14px}
label.f span{display:block;margin-bottom:5px;font-size:.92rem;color:var(--ink-2)}
input,select,textarea{width:100%;font:inherit;color:var(--ink);background:var(--card);border:1.5px solid var(--line);border-radius:10px;padding:10px 12px}
input:focus,select:focus,textarea:focus{outline:none;border-color:var(--brand);box-shadow:0 0 0 3px var(--brand-soft)}
input[type=checkbox],input[type=radio]{width:auto}
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--r-l);padding:20px;box-shadow:var(--shadow)}
.row{display:flex;gap:12px;flex-wrap:wrap;align-items:center}
.grid{display:grid;gap:16px}
.g2{grid-template-columns:repeat(auto-fit,minmax(280px,1fr))}
.g3{grid-template-columns:repeat(auto-fit,minmax(240px,1fr))}
.chip{display:inline-flex;align-items:center;gap:6px;padding:3px 10px;border-radius:99px;background:var(--brand-soft);font-weight:600;font-size:.82rem}
.chip.free{background:var(--mint-soft);color:var(--ok)}
.chip.lock{background:var(--line-2);color:var(--ink-2)}
.chip.soon{background:var(--sun-soft)}
.chip.err{background:var(--err-soft);color:var(--err)}
section.blk{padding:44px 0}
.msg{padding:12px 14px;border-radius:12px;margin:12px 0;font-weight:500}
.msg.err{background:var(--err-soft);color:var(--err)}.msg.ok{background:var(--mint-soft);color:var(--ok)}.msg.info{background:var(--sky-soft)}
table.t{width:100%;border-collapse:collapse;font-size:.95rem}
table.t th,table.t td{padding:9px 12px;text-align:left;border-bottom:1px solid var(--line);vertical-align:top}
table.t th{font-weight:700;background:var(--line-2)}
.tablewrap{overflow-x:auto;border:1px solid var(--line);border-radius:14px;background:var(--card);margin:1em 0}
#toast{position:fixed;left:50%;bottom:22px;transform:translateX(-50%) translateY(30px);opacity:0;background:var(--ink);color:var(--paper);padding:11px 18px;border-radius:12px;font-weight:600;z-index:90;transition:.25s;pointer-events:none;max-width:90vw}
#toast.show{opacity:1;transform:translateX(-50%)}
.modal-bg{position:fixed;inset:0;background:rgba(8,12,30,.6);display:grid;place-items:center;z-index:80;padding:16px}
.modal{background:var(--card);border-radius:var(--r-l);padding:24px;max-width:520px;width:100%;max-height:90vh;overflow:auto;border:1px solid var(--line)}

/* Hero --------------------------------------------------------------- */
.hero{padding:46px 16px 30px;display:grid;grid-template-columns:1.05fr 1fr;gap:34px;align-items:center}
.hero h1 .hl{background:linear-gradient(transparent 62%,var(--sun) 62%);padding:0 .1em}
.hero p.lead{font-size:1.18rem;color:var(--ink-2);max-width:34ch}
.pillrow{display:flex;gap:8px;flex-wrap:wrap;margin:18px 0 0}
.pillrow span{background:var(--card);border:1px solid var(--line);padding:5px 12px;border-radius:99px;font-weight:600;font-size:.88rem}
@media (max-width:900px){.hero{grid-template-columns:1fr}}

/* Code editor + console ------------------------------------------------- */
.ed{position:relative;border-radius:var(--r-m);background:var(--code-bg);color:var(--code-ink);overflow:hidden;border:1px solid #232c55;font:400 14.5px/1.55 var(--f-mono)}
.ed .gut,.ed .hl,.ed textarea{font:inherit;padding:12px 0}
.ed-in{position:relative;display:flex;max-height:62vh;overflow:auto}
.ed .gut{flex:none;min-width:42px;text-align:right;color:var(--code-dim);padding-right:10px;user-select:none;white-space:pre;background:rgba(255,255,255,.03)}
.ed .gut .bad{color:#FF6B81;font-weight:700}
.ed .body{position:relative;flex:1;min-width:0}
.ed pre.hl{margin:0;padding:12px 14px;white-space:pre;pointer-events:none;min-height:100%;tab-size:4}
.ed textarea{position:absolute;inset:0;width:100%;height:100%;padding:12px 14px;background:transparent;color:transparent;caret-color:#FFC93C;border:0;border-radius:0;resize:none;white-space:pre;overflow:hidden;tab-size:4;box-shadow:none!important}
.ed textarea:focus{outline:none}
.ed.ro textarea{caret-color:transparent}
.ed .tk-k{color:#FF8FB1}.ed .tk-t{color:#7FDBFF}.ed .tk-s{color:#A6F0B4}.ed .tk-n{color:#FFD27A}.ed .tk-c{color:#6F7BA6;font-style:italic}.ed .tk-m{color:#B9A8FF}
.ed .errline{background:rgba(255,80,110,.18);display:inline-block;width:100%}
.ed .curline{background:rgba(255,201,60,.22);display:inline-block;width:100%}
.ed-bar{display:flex;align-items:center;gap:8px;padding:8px 10px;background:#0A0F25;border-top:1px solid #232c55;flex-wrap:wrap}
.ed-bar .lbl{color:var(--code-dim);font:600 .8rem var(--f-body);margin-right:auto}
.con{background:#070B1C;color:#DDE5FF;border-radius:var(--r-m);margin-top:10px;font:400 14px/1.5 var(--f-mono);border:1px solid #232c55}
.con-h{padding:6px 12px;color:var(--code-dim);font:600 .78rem var(--f-body);border-bottom:1px solid #1b2347;display:flex;justify-content:space-between}
.con pre{margin:0;padding:10px 14px;white-space:pre-wrap;word-break:break-word;max-height:300px;overflow:auto}
.con .e{color:#FF7A8F}.con .i{color:#7FDBFF}.con .ok{color:#6BEFC1}
.con-in{display:flex;gap:8px;padding:0 12px 12px}
.con-in input{background:#0E1430;color:#fff;border-color:#2d3868;font-family:var(--f-mono)}
.stdin{margin-top:8px}.stdin textarea{font-family:var(--f-mono);min-height:56px;background:#0E1430;color:#fff;border-color:#2d3868}
.stdin span{font-size:.8rem;color:var(--ink-2);font-weight:600}
.cerr{background:var(--err-soft);border:1px solid var(--err);color:var(--ink);border-radius:var(--r-m);padding:12px 14px;margin-top:10px;font-size:.95rem}
.cerr pre{margin:6px 0;font:500 13.5px var(--f-mono);white-space:pre-wrap;color:var(--err)}
.cerr b{color:var(--err)}
.verdict{margin-top:10px;border-radius:var(--r-m);padding:12px 14px;font-weight:600}
.verdict.ok{background:var(--mint-soft);color:var(--ok)}.verdict.no{background:var(--err-soft);color:var(--err)}
.tests{display:grid;gap:6px;margin-top:8px}
.tc{display:flex;gap:10px;align-items:flex-start;padding:8px 12px;border-radius:10px;background:var(--card);border:1px solid var(--line);font-size:.92rem}
.tc.p{border-left:5px solid var(--mint)}.tc.f{border-left:5px solid var(--err)}
.tc pre{margin:4px 0 0;font:13px var(--f-mono);white-space:pre-wrap}

/* Lesson page --------------------------------------------------------------- */
.lesson{display:grid;grid-template-columns:250px 1fr;gap:34px;padding:26px 0 80px}
.side{position:sticky;top:78px;align-self:start;max-height:calc(100vh - 96px);overflow:auto;font-size:.92rem}
.side a{display:block;padding:6px 10px;border-radius:8px;color:var(--ink-2);text-decoration:none;font-weight:500}
.side a:hover{background:var(--brand-soft)}.side a.on{background:var(--brand);color:var(--brand-ink)}
.lbody{min-width:0}
.lbody>*+*{margin-top:0}
.lhead{border-radius:var(--r-l);padding:26px;margin-bottom:26px;color:#fff;position:relative;overflow:hidden}
.lhead h1{font-size:clamp(1.7rem,4vw,2.5rem);margin:6px 0}
.lhead .em{font-size:3rem;position:absolute;right:20px;top:10px;opacity:.9}
.lhead p{max-width:50ch;margin:0;opacity:.95}
.lbody h2{margin-top:1.6em;scroll-margin-top:80px;display:flex;align-items:center;gap:10px}
.lbody h2::before{content:'';width:10px;height:28px;border-radius:4px;background:var(--lc,var(--brand))}
.callout{display:flex;gap:12px;border-radius:var(--r-m);padding:14px 16px;margin:16px 0;border:1.5px solid}
.callout .ic{font-size:1.4rem;line-height:1.3}
.callout p:last-child{margin:0}
.callout.tip{background:var(--mint-soft);border-color:var(--mint)}.callout.warn{background:var(--sun-soft);border-color:var(--sun)}
.callout.note{background:var(--sky-soft);border-color:var(--sky)}.callout.why{background:var(--brand-soft);border-color:var(--brand)}
.callout.trap{background:var(--coral-soft);border-color:var(--coral)}
.lbody ul,.lbody ol{padding-left:1.3em;margin:0 0 1em}.lbody li{margin:.3em 0}
.cap{font-size:.88rem;color:var(--ink-2);margin:6px 2px 16px}
.runbox{margin:16px 0}
.quiz{border:2px solid var(--ink);border-radius:var(--r-l);padding:18px;margin:22px 0;background:var(--card);box-shadow:4px 4px 0 var(--lc,var(--brand))}
.quiz .q{font-weight:700;margin-bottom:10px}
.opt{display:block;width:100%;text-align:left;margin:6px 0;padding:10px 14px;border-radius:12px;border:1.5px solid var(--line);background:var(--paper);color:var(--ink);font:inherit;cursor:pointer}
.opt:hover:not([disabled]){border-color:var(--brand)}
.opt.right{background:var(--mint-soft);border-color:var(--mint)}.opt.wrong{background:var(--err-soft);border-color:var(--err)}
.quiz .why{margin-top:8px;font-size:.95rem}
.prog{height:8px;background:var(--line);border-radius:9px;overflow:hidden}.prog i{display:block;height:100%;background:var(--mint)}
@media (max-width:900px){.lesson{grid-template-columns:1fr}.side{position:static;max-height:none;display:flex;gap:6px;overflow:auto;padding-bottom:6px}.side a{white-space:nowrap}}

/* Anim widgets ------------------------------------------------------------ */
.anim{border:2px dashed var(--line);border-radius:var(--r-l);padding:16px;margin:20px 0;background:var(--card)}
.anim-h{display:flex;align-items:center;gap:8px;font-weight:700;margin-bottom:10px;flex-wrap:wrap}
.anim-h small{font-weight:500;color:var(--ink-2)}
.anim-stage{min-height:120px;display:flex;flex-direction:column;gap:12px;align-items:center;justify-content:center;overflow-x:auto;padding:6px 0}
.anim-ctl{display:flex;gap:8px;justify-content:center;flex-wrap:wrap;margin-top:12px;align-items:center}
.anim-say{text-align:center;font-weight:600;min-height:3em;margin-top:8px}
.cells{display:flex;gap:6px;align-items:flex-end}
.cell{min-width:44px;height:44px;border-radius:10px;border:2px solid var(--ink);display:grid;place-items:center;font:700 1rem var(--f-mono);background:var(--card);position:relative;transition:transform .35s,background .25s,height .35s}
.cell small{position:absolute;top:100%;margin-top:3px;font:500 .72rem var(--f-mono);color:var(--ink-3)}
.cell.a{background:var(--sun);color:#14213D}.cell.b{background:var(--coral);color:#fff}.cell.g{background:var(--mint);color:#06281F}.cell.d{opacity:.35}.cell.s{background:var(--sky);color:#06281F}
.cell.ptr::before{content:'▼';position:absolute;bottom:100%;font-size:.8rem;color:var(--brand)}
.box{border:2px solid var(--ink);border-radius:12px;padding:6px 14px;background:var(--card);font-family:var(--f-mono);font-weight:600;display:inline-flex;flex-direction:column;align-items:center;min-width:70px}
.box small{font:600 .72rem var(--f-body);color:var(--ink-2)}
.pill{display:inline-block;padding:2px 10px;border-radius:99px;font:600 .85rem var(--f-mono);background:var(--brand-soft)}
.stackcol{display:flex;flex-direction:column-reverse;gap:4px;min-width:200px}
.frame{border:2px solid var(--ink);border-radius:10px;padding:6px 12px;background:var(--sun-soft);font:600 .9rem var(--f-mono);animation:pop .3s}
.frame.top{background:var(--sun)}
.frame.done{background:var(--mint-soft)}
@keyframes pop{from{transform:scale(.7);opacity:0}to{transform:none;opacity:1}}
.svgfig{max-width:100%;height:auto}

/* Flowchart ------------------------------------------------------------------ */
.flowsvg{max-width:100%;height:auto;display:block;margin:auto}
.flowsvg .sh{fill:var(--card);stroke:var(--ink);stroke-width:2}
.flowsvg .t-start .sh{fill:var(--mint-soft)}.flowsvg .t-io .sh{fill:var(--sky-soft)}.flowsvg .t-d .sh{fill:var(--sun-soft)}.flowsvg .t-p .sh{fill:var(--brand-soft)}
.flowsvg text{fill:var(--ink);font:600 14px var(--f-mono);text-anchor:middle;dominant-baseline:central}
.flowsvg .ln{stroke:var(--ink);stroke-width:2;fill:none}
.flowsvg .ar{fill:var(--ink)}
.flowsvg .lb{font:700 12px var(--f-body);fill:var(--brand)}
.flowsvg .on .sh{stroke:var(--coral);stroke-width:4}

/* Trace viewer ----------------------------------------------------------------- */
.tv{border:1px solid var(--line);border-radius:var(--r-l);background:var(--card);padding:12px;margin:16px 0}
.tv-grid{display:grid;grid-template-columns:minmax(0,1.15fr) minmax(0,1fr);gap:12px}
@media (max-width:860px){.tv-grid{grid-template-columns:1fr}}
.tv-ctl{display:flex;gap:6px;align-items:center;flex-wrap:wrap;margin-bottom:10px}
.tv-ctl input[type=range]{flex:1;min-width:120px;padding:0;accent-color:var(--brand)}
.tv-say{background:var(--sun-soft);border-radius:12px;padding:10px 14px;margin-bottom:10px;font-weight:600;min-height:3.2em}
.tv-say code{background:rgba(0,0,0,.08)}
.tv-pane{background:var(--paper);border:1px solid var(--line);border-radius:12px;padding:10px;margin-bottom:10px}
.tv-pane h4{margin:0 0 6px;font:700 .85rem var(--f-body);color:var(--ink-2)}
.tv-frame{border:2px solid var(--ink);border-radius:10px;margin-bottom:6px;overflow:hidden;background:var(--card)}
.tv-frame>b{display:block;background:var(--ink);color:var(--paper);padding:2px 10px;font:600 .82rem var(--f-mono)}
.tv-frame.top>b{background:var(--brand);color:#fff}
.tv-var{display:flex;justify-content:space-between;gap:10px;padding:3px 10px;font:500 .9rem var(--f-mono);border-top:1px dashed var(--line)}
.tv-var .ty{color:var(--ink-3)}
.tv-var.chg{background:var(--sun);color:#14213D;animation:flash .8s}
@keyframes flash{from{background:var(--coral)}to{background:var(--sun)}}
.tv-arr{display:flex;gap:3px;flex-wrap:wrap;margin:4px 0 10px}
.tv-arr .c{min-width:36px;text-align:center;border:2px solid var(--ink);border-radius:8px;padding:2px 6px;font:600 .88rem var(--f-mono);position:relative;margin-bottom:14px;background:var(--card)}
.tv-arr .c small{position:absolute;top:100%;left:0;right:0;font:500 .66rem var(--f-mono);color:var(--ink-3)}
.tv-arr .c.chg{background:var(--sun);color:#14213D}
.tv-out{background:#070B1C;color:#DDE5FF;font:13.5px/1.45 var(--f-mono);padding:10px;border-radius:10px;white-space:pre-wrap;min-height:44px;max-height:200px;overflow:auto}

/* Courses / catalog ----------------------------------------------------------------- */
.lcard{display:flex;gap:14px;align-items:center;padding:14px 16px;border-radius:var(--r-m);border:1px solid var(--line);background:var(--card);text-decoration:none;color:var(--ink);transition:transform .12s,border-color .12s}
.lcard:hover{transform:translateY(-2px);border-color:var(--c,var(--brand))}
.lcard .em{width:48px;height:48px;border-radius:14px;display:grid;place-items:center;font-size:1.5rem;background:var(--c,var(--brand));flex:none}
.lcard h3{margin:0;font-size:1.05rem}.lcard small{color:var(--ink-2)}
.lcard .mid{flex:1;min-width:0}
.lcard.locked{opacity:.78}
.unit{margin:30px 0 10px;font:700 1.1rem var(--f-display);color:var(--ink-2);display:flex;gap:10px;align-items:center}
.unit::after{content:'';flex:1;height:2px;background:var(--line)}
.price{font:800 2.4rem var(--f-display)}.price s{font-size:1.2rem;color:var(--ink-3);margin-left:8px}
.steps{counter-reset:s;list-style:none;padding:0}
.steps li{counter-increment:s;padding-left:46px;position:relative;margin:14px 0}
.steps li::before{content:counter(s);position:absolute;left:0;top:-2px;width:32px;height:32px;border-radius:50%;background:var(--sun);color:#14213D;font:800 1rem var(--f-display);display:grid;place-items:center}
.tabs{display:flex;gap:6px;flex-wrap:wrap;margin:14px 0}
.tabs button{border:1.5px solid var(--line);background:var(--card);color:var(--ink);padding:7px 14px;border-radius:99px;font:600 .92rem var(--f-body);cursor:pointer}
.tabs button.on{background:var(--ink);color:var(--paper);border-color:var(--ink)}
.task{border:1px solid var(--line);border-radius:var(--r-l);background:var(--card);padding:18px;margin:16px 0}
.task>h3{display:flex;align-items:center;gap:10px;flex-wrap:wrap}
.sample{display:grid;grid-template-columns:1fr 1fr;gap:8px;margin:8px 0}
.sample pre{margin:0;padding:8px 12px;background:var(--line-2);border-radius:10px;font:13.5px var(--f-mono);white-space:pre-wrap}
.sample b{display:block;font-size:.78rem;color:var(--ink-2);margin-bottom:2px}
@media (max-width:560px){.sample{grid-template-columns:1fr}}
details.hint{margin:8px 0;border-radius:10px;background:var(--sun-soft);padding:8px 12px}
details.hint summary{cursor:pointer;font-weight:700}
footer#foot{border-top:1px solid var(--line);padding:30px 0 50px;color:var(--ink-2);font-size:.92rem;margin-top:30px}
.dev{display:grid;grid-template-columns:auto 1fr;gap:24px;align-items:center}
.avatar{width:120px;height:120px;border-radius:50%;background:linear-gradient(135deg,var(--brand),var(--coral));display:grid;place-items:center;font:800 2.6rem var(--f-display);color:#fff}
@media (max-width:560px){.dev{grid-template-columns:1fr}}
.soon-box{border:2px dashed var(--line);border-radius:var(--r-l);padding:22px;text-align:center;background:var(--card)}
.stat{font:800 2rem var(--f-display)}
@media (max-width:820px){.coursehead{grid-template-columns:1fr!important}}
.lead{font-size:1.1rem}
.hero>*,.lesson>*,.grid>*{min-width:0}

/* ===== Colourful living background (no grid) ===== */
:root{--bg1:rgba(91,75,255,.30);--bg2:rgba(255,92,138,.26);--bg3:rgba(18,199,154,.26);--bg4:rgba(255,201,60,.34);--bgbase:#F7F5FF}
:root[data-theme=dark]{--bg1:rgba(110,92,255,.34);--bg2:rgba(255,92,138,.20);--bg3:rgba(18,199,154,.18);--bg4:rgba(255,201,60,.12);--bgbase:#0B1022}
body{background:var(--bgbase)}
.bgfx{position:fixed;inset:0;z-index:-1;overflow:hidden;pointer-events:none;
  background:
   radial-gradient(70vmax 55vmax at 0% 0%,var(--bg1),transparent 60%),
   radial-gradient(60vmax 50vmax at 100% 8%,var(--bg2),transparent 58%),
   radial-gradient(65vmax 55vmax at 100% 100%,var(--bg3),transparent 60%),
   radial-gradient(55vmax 45vmax at 0% 100%,var(--bg4),transparent 60%)}
.bgfx i{position:absolute;border-radius:50%;filter:blur(50px);opacity:.55;animation:drift 22s ease-in-out infinite alternate}
.bgfx i:nth-child(1){width:34vmax;height:34vmax;left:-8vmax;top:18vh;background:var(--bg1)}
.bgfx i:nth-child(2){width:28vmax;height:28vmax;right:-6vmax;top:-6vmax;background:var(--bg2);animation-delay:-6s;animation-duration:26s}
.bgfx i:nth-child(3){width:30vmax;height:30vmax;right:10vw;bottom:-12vmax;background:var(--bg3);animation-delay:-11s}
.bgfx i:nth-child(4){width:24vmax;height:24vmax;left:30vw;bottom:-6vmax;background:var(--bg4);animation-delay:-3s;animation-duration:30s}
.bgfx b{position:absolute;display:block;opacity:.55;animation:bob 9s ease-in-out infinite alternate}
.bgfx .s1{left:7%;top:24%;width:26px;height:26px;border:5px solid var(--sun);border-radius:50%}
.bgfx .s2{right:9%;top:38%;width:0;height:0;border-left:15px solid transparent;border-right:15px solid transparent;border-bottom:26px solid var(--coral);animation-delay:-2s}
.bgfx .s3{left:14%;bottom:16%;width:22px;height:22px;background:var(--mint);border-radius:6px;transform:rotate(18deg);animation-delay:-4s}
.bgfx .s4{right:16%;bottom:22%;width:30px;height:30px;border:5px solid var(--brand);border-radius:50%;animation-delay:-6s}
.bgfx .s5{left:46%;top:12%;width:18px;height:18px;background:var(--sky);border-radius:50%;animation-delay:-3s}
.bgfx .s6{left:60%;bottom:10%;width:0;height:0;border-left:11px solid transparent;border-right:11px solid transparent;border-bottom:19px solid var(--sun);animation-delay:-5s}
@keyframes drift{from{transform:translate(0,0) scale(1)}to{transform:translate(6vw,-5vh) scale(1.18)}}
@keyframes bob{from{transform:translateY(0) rotate(0)}to{transform:translateY(-22px) rotate(25deg)}}
@media (prefers-reduced-motion:reduce){.bgfx i,.bgfx b{animation:none}}
/* header: frosted, colourful */
#top{background:color-mix(in srgb,var(--paper) 72%,transparent)}
.brand i{background:linear-gradient(135deg,var(--brand),var(--coral));box-shadow:0 4px 12px -4px var(--brand)}
.brand span{background:linear-gradient(90deg,var(--brand),var(--coral));-webkit-background-clip:text;background-clip:text;color:transparent}
.nav a{display:inline-flex;align-items:center;gap:6px}
.nav a[aria-current]{background:var(--brand);color:var(--brand-ink)}
.card,.lcard,.task,.tv,.anim,.soon-box,.tablewrap{backdrop-filter:blur(2px)}
.xpchip{display:inline-flex;align-items:center;gap:6px;padding:4px 12px;border-radius:99px;font:700 .88rem var(--f-body);background:linear-gradient(90deg,var(--sun),#FFB347);color:#14213D;text-decoration:none}

/* ===== Tabs inside CSE110, levels, practice ===== */
.ctabs{display:flex;gap:8px;flex-wrap:wrap;margin:0 0 22px}
.ctabs a{padding:9px 16px;border-radius:99px;background:var(--card);border:1.5px solid var(--line);color:var(--ink);text-decoration:none;font-weight:700;font-size:.95rem}
.ctabs a:hover{border-color:var(--brand)}
.ctabs a.on{background:var(--ink);color:var(--paper);border-color:var(--ink)}
.lv{display:inline-flex;align-items:center;gap:4px;padding:2px 10px;border-radius:99px;font:700 .78rem var(--f-body);text-transform:uppercase;letter-spacing:.03em}
.lv.easy{background:var(--mint-soft);color:var(--ok)}.lv.medium{background:var(--sun-soft);color:#8A6200}.lv.hard{background:var(--coral-soft);color:#C2185B}
:root[data-theme=dark] .lv.medium{color:#FFD27A}:root[data-theme=dark] .lv.hard{color:#FF8FB1}
.xpb{font:700 .8rem var(--f-body);color:var(--ink-2)}
.pset{display:flex;flex-direction:column;gap:10px;padding:18px;border-radius:var(--r-l);background:var(--card);border:1px solid var(--line);text-decoration:none;color:var(--ink);position:relative;overflow:hidden;transition:transform .12s,box-shadow .12s}
.pset::before{content:'';position:absolute;left:0;top:0;right:0;height:6px;background:var(--c,var(--brand))}
.pset:hover{transform:translateY(-3px);box-shadow:0 14px 30px -16px var(--c,var(--brand))}
.pset .em{width:50px;height:50px;border-radius:15px;display:grid;place-items:center;font-size:1.6rem;background:var(--c,var(--brand))}
.pset h3{margin:0}
.pq{border:1px solid var(--line);border-radius:var(--r-m);background:var(--card);margin:10px 0;overflow:hidden}
.pq.solved{border-color:var(--mint)}
.pq>summary{list-style:none;cursor:pointer;display:flex;gap:10px;align-items:center;padding:12px 16px;font-weight:700;flex-wrap:wrap}
.pq>summary::-webkit-details-marker{display:none}
.pq>summary .tick{width:26px;height:26px;border-radius:50%;border:2px solid var(--line);display:grid;place-items:center;font-size:.9rem;flex:none}
.pq.solved>summary .tick{background:var(--mint);border-color:var(--mint);color:#06281F}
.pq>summary .sp{flex:1}
.pq .pqb{padding:4px 16px 18px;border-top:1px dashed var(--line)}
.pq .task{border:0;padding:0;margin:0;background:none}.pq .task>h3{display:none}
.daily{display:flex;gap:16px;align-items:center;flex-wrap:wrap;background:linear-gradient(120deg,var(--brand),var(--coral));color:#fff;border-radius:var(--r-l);padding:20px 22px}
.daily h3{margin:0;color:#fff}.daily .btn{background:#fff;color:#14213D;border-color:#14213D;box-shadow:3px 3px 0 #14213D}
.fchips{display:flex;gap:8px;flex-wrap:wrap;margin:14px 0}
.fchips button{border:1.5px solid var(--line);background:var(--card);color:var(--ink);padding:6px 14px;border-radius:99px;font:700 .9rem var(--f-body);cursor:pointer}
.fchips button.on{background:var(--brand);color:var(--brand-ink);border-color:var(--brand)}

/* ===== Progress + leaderboard ===== */
.xhero{display:flex;gap:22px;align-items:center;flex-wrap:wrap;background:linear-gradient(135deg,var(--card),var(--brand-soft))}
.xav{width:84px;height:84px;border-radius:26px;background:linear-gradient(135deg,var(--brand),var(--coral));color:#fff;display:grid;place-items:center;font:800 2.4rem var(--f-display);box-shadow:4px 4px 0 var(--sun)}
.xbar{height:14px;border-radius:99px;background:var(--line);overflow:hidden;margin-bottom:6px}
.xbar i{display:block;height:100%;border-radius:99px;background:linear-gradient(90deg,var(--sun),var(--coral),var(--brand));transition:width .6s}
.xstats{display:flex;gap:18px;flex-wrap:wrap}
.xstats div{text-align:center;min-width:74px}.xstats b{display:block;font:800 1.5rem var(--f-display)}.xstats small{color:var(--ink-2)}
.badges{display:grid;grid-template-columns:repeat(auto-fill,minmax(150px,1fr));gap:12px}
.badge{border:2px dashed var(--line);border-radius:var(--r-m);padding:14px 10px;text-align:center;background:var(--card);opacity:.62}
.badge.on{opacity:1;border:2px solid var(--sun);background:linear-gradient(180deg,var(--sun-soft),var(--card));animation:pop .4s}
.badge .bi{font-size:2rem}.badge small{display:block;color:var(--ink-2);font-size:.78rem;line-height:1.3;margin-top:2px}
.heat{display:grid;grid-template-columns:repeat(7,1fr);gap:5px;max-width:320px;margin-bottom:10px}
.hm{aspect-ratio:1;border-radius:6px;background:var(--line-2);display:block}
.hm.h1{background:#B9F0DE}.hm.h2{background:#6BE0BC}.hm.h3{background:#12C79A}.hm.h4{background:#0A8F6E}
.podium{display:grid;grid-template-columns:1fr 1.15fr 1fr;gap:10px;align-items:end;margin:18px 0}
.pod{background:var(--card);border:2px solid var(--ink);border-radius:var(--r-l);padding:14px 8px;text-align:center;min-width:0;overflow:hidden}
.pod b{display:block;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.pod small{display:block;color:var(--ink-2);overflow:hidden;text-overflow:ellipsis;white-space:nowrap;min-height:1.4em}
.pod .pm{font-size:2.2rem}.pod .pv{font:800 1.05rem var(--f-display);margin-top:4px}
.pod.p1{background:linear-gradient(180deg,#FFE9A8,var(--card));padding-top:26px;padding-bottom:22px;box-shadow:4px 4px 0 var(--sun)}
.pod.p2{background:linear-gradient(180deg,#E3E9F7,var(--card))}.pod.p3{background:linear-gradient(180deg,#FFD9C2,var(--card))}
:root[data-theme=dark] .pod.p1{background:linear-gradient(180deg,#4A3D12,var(--card))}:root[data-theme=dark] .pod.p2{background:linear-gradient(180deg,#2B3558,var(--card))}:root[data-theme=dark] .pod.p3{background:linear-gradient(180deg,#4A2C1E,var(--card))}
.pod.me{outline:3px solid var(--brand)}.pod.empty{opacity:.5}
.lb{display:grid;gap:8px}
.lbrow{display:flex;align-items:center;gap:12px;padding:10px 14px;background:var(--card);border:1px solid var(--line);border-radius:var(--r-m)}
.lbrow.me{border:2px solid var(--brand);background:var(--brand-soft)}
.lbrow .rk{font:800 1rem var(--f-display);min-width:42px;color:var(--ink-2)}
.lbrow b,.lbrow small{display:block;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
@media (max-width:520px){.podium{grid-template-columns:1fr 1.1fr 1fr;gap:6px}.pod .pm{font-size:1.7rem}.pod{padding:10px 4px}}

/* ===== Home ===== */
.hero h1 .g1{background:linear-gradient(90deg,var(--brand),var(--coral));-webkit-background-clip:text;background-clip:text;color:transparent}
.hero h1 .g2{background:linear-gradient(90deg,var(--coral),#FF9F1C);-webkit-background-clip:text;background-clip:text;color:transparent}
.mecard{display:flex;gap:14px;align-items:center;flex-wrap:wrap;padding:14px 16px}
.xav.sm{width:46px;height:46px;border-radius:14px;font-size:1.3rem;box-shadow:none}
.statrow{display:grid;grid-template-columns:repeat(4,1fr);gap:12px}
.bigstat{background:var(--card);border:1px solid var(--line);border-bottom:5px solid var(--c);border-radius:var(--r-l);padding:16px;text-align:center}
.bigstat b{display:block;font:800 2.3rem/1.1 var(--f-display);color:var(--c)}.bigstat span{color:var(--ink-2);font-weight:600}
@media (max-width:640px){.statrow{grid-template-columns:repeat(2,1fr)}}
.feat{border-top:6px solid var(--c)}
.feat .fi{width:52px;height:52px;border-radius:16px;display:grid;place-items:center;font-size:1.7rem;background:var(--c);margin-bottom:10px}
.ccard{display:block;border-radius:var(--r-l);padding:22px;color:#fff;text-decoration:none;background:linear-gradient(135deg,var(--brand),#8A3FFC 55%,var(--coral));box-shadow:0 18px 40px -20px var(--brand);transition:transform .15s}
.ccard:hover{transform:translateY(-4px) rotate(-.3deg)}
.ccard h3{color:#fff;font-size:1.5rem}.ccard .cc-top{display:flex;justify-content:space-between;align-items:center;margin-bottom:6px}
.ccard .chip.w{background:rgba(255,255,255,.22);color:#fff}
.ccard.soon{background:var(--card);color:var(--ink);border:2px dashed var(--line);box-shadow:none}.ccard.soon h3{color:var(--ink)}.ccard.soon:hover{transform:none}

/* ===== Course blocks ===== */
.cgrid{display:grid;grid-template-columns:repeat(auto-fill,minmax(290px,1fr));gap:20px;margin-top:22px}
.cblock{position:relative;display:flex;flex-direction:column;gap:8px;min-height:300px;padding:22px;border-radius:26px;color:#fff;text-decoration:none;overflow:hidden;background:linear-gradient(145deg,var(--c1),var(--c2));box-shadow:0 22px 40px -24px var(--c1);transition:transform .18s,box-shadow .18s}
.cblock::before{content:'';position:absolute;right:-60px;top:-60px;width:200px;height:200px;border-radius:50%;background:rgba(255,255,255,.16)}
.cblock::after{content:'';position:absolute;left:-40px;bottom:-70px;width:180px;height:180px;border-radius:50%;background:rgba(255,255,255,.10)}
.cblock>*{position:relative;z-index:1}
.cblock.live:hover{transform:translateY(-6px) rotate(-.6deg);box-shadow:0 30px 50px -22px var(--c1)}
.cblock h3{color:#fff;font-size:1.45rem;margin:0}
.cblock p{margin:0;opacity:.95;font-size:.98rem;line-height:1.5}
.cb-top{display:flex;justify-content:space-between;align-items:center}
.cb-code{background:rgba(255,255,255,.25);padding:3px 12px;border-radius:99px;font:800 .85rem var(--f-display);letter-spacing:.04em}
.cb-tag{background:rgba(0,0,0,.22);padding:3px 11px;border-radius:99px;font:700 .78rem var(--f-body)}.cb-tag.on{background:#fff;color:#0A6F55}
.cb-emoji{font-size:3.4rem;line-height:1.1;margin:6px 0 2px;filter:drop-shadow(0 6px 8px rgba(0,0,0,.2));animation:bob 5s ease-in-out infinite alternate}
.cb-pill{background:rgba(255,255,255,.22);padding:2px 10px;border-radius:99px;font:700 .8rem var(--f-body)}
.cb-cta{margin-top:auto;font:800 1rem var(--f-display)}
.cblock.soon{filter:saturate(.8);opacity:.93}
.cblock.soon .cb-cta{opacity:.9}
@media (prefers-reduced-motion:reduce){.cb-emoji{animation:none}}
.nav a{white-space:nowrap}
.only-m{display:none!important}
@media (max-width:820px){.only-m{display:block!important}}

/* ===== Smoothness: page enter, skeleton, scroll bar, search ===== */
#main.enter{animation:enter .38s cubic-bezier(.2,.7,.3,1)}
@keyframes enter{from{opacity:0;transform:translateY(10px)}to{opacity:1;transform:none}}
.skel{padding:40px 16px;display:grid;gap:14px;max-width:1100px;margin:0 auto}
.skel i{display:block;border-radius:16px;background:linear-gradient(90deg,var(--line-2) 25%,var(--card) 50%,var(--line-2) 75%);background-size:200% 100%;animation:shimmer 1.2s linear infinite}
.skel .s1{height:44px;width:42%}.skel .s2{height:20px;width:70%}.skel .s3{height:140px}.skel .s4{height:140px;width:85%}
@keyframes shimmer{to{background-position:-200% 0}}
#sbar{position:fixed;left:0;top:0;height:3px;width:100%;transform-origin:0 50%;transform:scaleX(0);background:linear-gradient(90deg,var(--brand),var(--coral),var(--sun));z-index:60;pointer-events:none}
.sbg{align-items:start;padding-top:12vh}
.smodal{background:var(--card);border:1px solid var(--line);border-radius:20px;width:100%;max-width:560px;box-shadow:0 30px 70px -20px rgba(0,0,0,.45);overflow:hidden}
.sin{display:flex;gap:10px;align-items:center;padding:12px 16px;border-bottom:1px solid var(--line)}
.sin input{border:0;box-shadow:none!important;padding:6px 0;font-size:1.05rem;background:transparent}
.sin kbd{font:600 .72rem var(--f-mono);border:1px solid var(--line);border-radius:6px;padding:2px 6px;color:var(--ink-3)}
.sres{max-height:52vh;overflow:auto;padding:6px}
.sres .sitem{display:flex;gap:12px;align-items:center;padding:9px 12px;border-radius:12px;text-decoration:none;color:var(--ink)}
.sres .sitem.on{background:var(--brand-soft)}
.sres .si{font-size:1.4rem;width:34px;text-align:center}.sres .st{flex:1;min-width:0}.sres .st b,.sres .st small{display:block;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}.sres .st small{color:var(--ink-2)}
@media (prefers-reduced-motion:reduce){#main.enter{animation:none}.skel i{animation:none}}

/* ===== v3: home nest, floating courses ===== */
.hero.home{grid-template-columns:1.05fr .95fr}
.hero.home h1{font-size:clamp(2.4rem,6vw,4rem);line-height:1.05;margin:0}
.rot{display:inline-block;color:var(--ink);animation:rotin .5s cubic-bezier(.2,1.4,.4,1)}
@keyframes rotin{from{opacity:0;transform:translateY(.5em) scale(.9)}to{opacity:1;transform:none}}
.nestart{max-width:460px;width:100%;margin:0 auto;color:var(--ink)}
.nestart svg{width:100%;height:auto;overflow:visible;filter:drop-shadow(0 24px 24px rgba(91,75,255,.22))}
.nestart .bird{transform-box:fill-box;transform-origin:50% 100%;animation:birdhop 3.4s ease-in-out infinite}
.nestart .egg{transform-box:fill-box;transform-origin:50% 100%;animation:wobble 3s ease-in-out infinite}
.nestart .e-b{animation-delay:-1.4s}
.nestart .wing{transform-box:fill-box;animation:flap 1.7s ease-in-out infinite}
.nestart .wl{transform-origin:100% 20%}.nestart .wr{transform-origin:0 20%;animation-direction:reverse}
.nestart .eyes{animation:blink 4.5s infinite;transform-box:fill-box;transform-origin:center}
.nestart .tuft{transform-box:fill-box;transform-origin:50% 100%;animation:wobble 2.2s ease-in-out infinite}
.nestart .spark path{transform-box:fill-box;transform-origin:center;animation:twinkle 2.4s ease-in-out infinite}
.nestart .spark path:nth-child(2){animation-delay:-.8s}.nestart .spark path:nth-child(3){animation-delay:-1.6s}
.nestart .orbit{transform-origin:180px 150px;animation:spin 22s linear infinite}
.nestart .orb{animation:spin 22s linear infinite reverse;transform-box:fill-box;transform-origin:center}
@keyframes birdhop{0%,100%{transform:translateY(0) scaleY(1)}45%{transform:translateY(-14px) scaleY(1.04)}60%{transform:translateY(0) scaleY(.94)}}
@keyframes wobble{0%,100%{transform:rotate(-5deg)}50%{transform:rotate(5deg)}}
@keyframes flap{0%,100%{transform:rotate(0)}50%{transform:rotate(-18deg)}}
@keyframes blink{0%,92%,100%{transform:scaleY(1)}96%{transform:scaleY(.1)}}
@keyframes twinkle{0%,100%{transform:scale(.6) rotate(0);opacity:.6}50%{transform:scale(1.25) rotate(25deg);opacity:1}}
@keyframes spin{to{transform:rotate(360deg)}}
.cgrid.float{grid-template-columns:repeat(auto-fit,minmax(280px,380px));justify-content:center;gap:28px}
.cblock.fl{animation:floaty 6s ease-in-out infinite;animation-delay:var(--d,0s)}
.cblock.fl:nth-child(even){animation-duration:7.5s}
@keyframes floaty{0%,100%{transform:translateY(0) rotate(-.7deg)}50%{transform:translateY(-14px) rotate(.7deg)}}
.cblock.live.fl:hover{animation-play-state:paused;transform:translateY(-10px) scale(1.03)}
.pop{animation:popin .6s cubic-bezier(.2,1.5,.4,1) both}
@keyframes popin{from{opacity:0;transform:scale(.7)}to{opacity:1;transform:none}}
.wob:hover{animation:wobble .5s ease-in-out}
@media (max-width:900px){.hero.home{grid-template-columns:1fr}.nestart{max-width:340px}}
@media (prefers-reduced-motion:reduce){.nestart *,.cblock.fl,.rot,.pop{animation:none!important}}

/* ===== v3: course dashboard, levels, exam ===== */
.tiles{display:grid;grid-template-columns:repeat(auto-fill,minmax(230px,1fr));gap:16px;margin-top:12px}
.tile{display:flex;flex-direction:column;gap:6px;padding:20px;border-radius:22px;color:#fff;text-decoration:none;background:linear-gradient(145deg,var(--c1),var(--c2));box-shadow:0 18px 30px -20px var(--c1);transition:transform .18s cubic-bezier(.2,1.4,.4,1),box-shadow .18s;position:relative;overflow:hidden}
.tile::after{content:'';position:absolute;right:-30px;bottom:-40px;width:120px;height:120px;border-radius:50%;background:rgba(255,255,255,.16)}
.tile:hover{transform:translateY(-6px) rotate(-1deg) scale(1.02);box-shadow:0 26px 36px -20px var(--c1)}
.tile h3{color:#fff;margin:0;font-size:1.25rem}.tile p{margin:0;opacity:.95;font-size:.95rem}
.tile .ti{font-size:2.4rem;line-height:1;transition:transform .3s}.tile:hover .ti{transform:scale(1.2) rotate(-8deg)}
.tile .prog.w{background:rgba(255,255,255,.3);margin-top:8px}.tile .prog.w i{background:#fff}
.lvgrid{display:grid;grid-template-columns:repeat(auto-fit,minmax(130px,1fr));gap:12px;margin:10px 0}
.lvcard{--lc:var(--brand);display:flex;flex-direction:column;gap:3px;align-items:center;text-align:center;padding:14px 8px;border-radius:20px;border:2px solid var(--lc);background:color-mix(in srgb,var(--lc) 10%,var(--card));cursor:pointer;font:inherit;color:var(--ink);transition:transform .15s cubic-bezier(.2,1.5,.4,1),box-shadow .15s}
.lvcard:hover{transform:translateY(-5px) scale(1.04);box-shadow:0 8px 0 -2px var(--lc)}
.lvcard .lvi{font-size:2rem;transition:transform .3s}.lvcard:hover .lvi{transform:scale(1.25) rotate(-10deg)}
.lvcard .prog{width:80%;margin:4px 0}
.lvcard.l1,.lv.l1{--lc:#12C79A}.lvcard.l2,.lv.l2{--lc:#2BA8F5}.lvcard.l3,.lv.l3{--lc:#FFB300}.lvcard.l4,.lv.l4{--lc:#FF5C8A}.lvcard.l5,.lv.l5{--lc:#7C3AED}
.lv.l1,.lv.l2,.lv.l3,.lv.l4,.lv.l5{background:color-mix(in srgb,var(--lc) 18%,var(--card));color:var(--ink);border:1.5px solid var(--lc);border-radius:99px;padding:2px 10px;font:700 .78rem var(--f-body);display:inline-block}
.examcard h3{margin:14px 0 6px;font-size:1rem}
.examhead{position:sticky;top:64px;z-index:20;background:var(--card);border:2px solid var(--line);border-radius:18px;padding:10px 14px;margin-bottom:14px;box-shadow:0 8px 20px -14px rgba(0,0,0,.3)}
.timer{font:800 1.5rem var(--f-display);font-variant-numeric:tabular-nums}.timer.low{color:var(--coral);animation:pulse .8s infinite}
@keyframes pulse{50%{transform:scale(1.12)}}
.examprog{height:6px;background:var(--line);border-radius:9px;margin-top:8px;overflow:hidden}.examprog i{display:block;height:100%;background:linear-gradient(90deg,var(--mint),var(--sun),var(--coral));transition:width 1s linear}
.dots{display:flex;gap:6px;flex-wrap:wrap}.dot{width:34px;height:34px;border-radius:50%;border:2px solid var(--line);background:var(--card);color:var(--ink);font-weight:800;cursor:pointer}
.dot.on{border-color:var(--brand);transform:scale(1.12)}.dot.ok{background:var(--mint);color:#06392c;border-color:var(--mint)}
.result{text-align:center;max-width:520px;margin:20px auto}.hrow{padding:8px 0;border-bottom:1px dashed var(--line)}
/* scroll reveal */
.rv{opacity:0;transform:translateY(18px);transition:opacity .5s ease,transform .5s cubic-bezier(.2,1.2,.4,1)}.rv.in{opacity:1;transform:none}
.tile.rv.in:hover{transform:translateY(-6px) rotate(-1deg) scale(1.02)}
@media (prefers-reduced-motion:reduce){.rv{opacity:1;transform:none;transition:none}}
.btn.coral{background:var(--coral);color:#fff;border-color:#14213D;box-shadow:3px 3px 0 #14213D}

/* ===== v3: fun micro-interactions ===== */
.btn{transition:transform .12s cubic-bezier(.2,1.6,.4,1),box-shadow .12s}
.btn:hover{transform:translateY(-2px) rotate(-.6deg)}.btn:active{transform:translate(2px,2px) scale(.97);box-shadow:none}
.brand:hover .logo,.logo:hover{animation:wobble .6s ease-in-out}
.lcard,.pset,.card.feat,.ccard{transition:transform .18s cubic-bezier(.2,1.4,.4,1),box-shadow .18s}
.lcard:hover,.pset:hover,.card.feat:hover{transform:translateY(-4px) scale(1.012)}
.tick{transition:transform .3s cubic-bezier(.2,1.8,.4,1)}.solved .tick{animation:popin .5s both}
.xpchip{animation:popin .5s both}
@keyframes wobble{0%,100%{transform:rotate(-5deg)}50%{transform:rotate(5deg)}}
@media (prefers-reduced-motion:reduce){.btn,.lcard,.pset{transition:none}.btn:hover,.lcard:hover,.pset:hover{transform:none}}

/* ===== v3: admin ===== */
.tabs button .badge{display:inline-block;margin-left:6px;min-width:20px;padding:0 6px;border-radius:99px;background:var(--coral);color:#fff;font:800 .72rem var(--f-body);line-height:19px}
.tabs button.on .badge{background:var(--sun);color:#14213D}
.strow:hover{background:var(--line-2)}
.paycard .chip{margin:0}
@media (max-width:640px){table.t{font-size:.85rem}}

/* ===== brand: real StudyNest logo ===== */
.brand img.logo{width:38px;height:38px;border-radius:11px;background:#fff;padding:2px;box-shadow:0 4px 12px -6px rgba(31,58,138,.5)}
.brand span{background:none!important;-webkit-background-clip:initial!important;background-clip:initial!important;color:inherit!important}
.brand .s1{color:#14286B}.brand .s2{color:#1FAE8A}
:root[data-theme="dark"] .brand .s1{color:#E8EEFF}
@media (prefers-color-scheme:dark){:root:not([data-theme="light"]) .brand .s1{color:#E8EEFF}}
.hero.home h1 .g1{background:linear-gradient(90deg,#14286B 0%,#1F6FD8 45%,#1FAE8A 100%);-webkit-background-clip:text;background-clip:text;color:transparent}

/* ===== v3: phone & tablet ===== */
#bnav{display:none}
@media (max-width:820px){
  body{padding-bottom:calc(68px + env(safe-area-inset-bottom))}
  #bnav{display:grid;grid-template-columns:repeat(5,1fr);position:fixed;left:0;right:0;bottom:0;z-index:60;background:color-mix(in srgb,var(--card) 92%,transparent);backdrop-filter:blur(14px);-webkit-backdrop-filter:blur(14px);border-top:1.5px solid var(--line);padding:6px 4px calc(6px + env(safe-area-inset-bottom))}
  #bnav a{display:flex;flex-direction:column;align-items:center;gap:1px;padding:5px 2px;border-radius:14px;color:var(--ink-2);text-decoration:none;font:700 .68rem var(--f-body);min-height:48px;justify-content:center;-webkit-tap-highlight-color:transparent;transition:transform .15s cubic-bezier(.2,1.6,.4,1)}
  #bnav a i{font-style:normal;font-size:1.35rem;line-height:1}
  #bnav a.on{background:var(--brand-soft);color:var(--ink)}
  #bnav a.on i{transform:translateY(-2px) scale(1.15)}
  #bnav a:active{transform:scale(.92)}
  #toast{bottom:calc(84px + env(safe-area-inset-bottom))!important}
  #foot{padding-bottom:12px}
  /* horizontally swipeable tab rows instead of wrapping */
  .ctabs,.tabs,.fchips{flex-wrap:nowrap;overflow-x:auto;-webkit-overflow-scrolling:touch;scrollbar-width:none;margin-left:-14px;margin-right:-14px;padding:2px 14px 8px;scroll-snap-type:x proximity}
  .ctabs::-webkit-scrollbar,.tabs::-webkit-scrollbar,.fchips::-webkit-scrollbar{display:none}
  .ctabs a,.tabs button,.fchips button{flex:0 0 auto;scroll-snap-align:start;white-space:nowrap}
  /* bigger touch targets, no iOS zoom on focus */
  .btn,.ibtn,.tabs button,.fchips button,.ctabs a{min-height:42px}
  .btn.sm{min-height:38px}
  input,select,textarea{font-size:16px!important}
  .wrap{padding-left:14px;padding-right:14px}
  h1{font-size:clamp(1.6rem,7vw,2.2rem)}
  .tiles{grid-template-columns:repeat(2,1fr);gap:12px}
  .tile{padding:16px}.tile h3{font-size:1.05rem}.tile p{font-size:.85rem}
  .cgrid.float{grid-template-columns:1fr}
  .grid.g3{grid-template-columns:1fr}
  .lvgrid{grid-template-columns:repeat(3,1fr)}
  .examhead .row{gap:8px}.examhead{top:58px}.timer{font-size:1.2rem}
  .dot{width:38px;height:38px}
  .modal{width:calc(100vw - 24px)!important;max-height:86vh;overflow:auto}
  .paycard .row{gap:8px}
  .tablewrap{-webkit-overflow-scrolling:touch}
  .row{gap:8px}
  .cb-emoji{font-size:2.6rem}
}
@media (max-width:420px){.tiles{grid-template-columns:1fr 1fr}.lvgrid{grid-template-columns:repeat(2,1fr)}.statrow{grid-template-columns:repeat(2,1fr)}}
/* tablets: two-column course head, roomy grids */
@media (min-width:821px) and (max-width:1100px){.tiles{grid-template-columns:repeat(3,1fr)}.wrap{padding-left:20px;padding-right:20px}}
/* installed app: hide the DEV banner spacing, respect notches */
@media (display-mode:standalone){#top{padding-top:env(safe-area-inset-top)}.instbtn{display:none}}
@media (hover:none){.lcard:hover,.pset:hover,.tile:hover,.card.feat:hover,.btn:hover{transform:none}}
@media (max-width:820px){
  .instbtn{display:none!important}
  .bar{gap:6px}
  .brand{font-size:1.18rem;gap:7px;min-width:0}
  .brand img.logo{width:34px;height:34px}
  .tools{gap:5px;flex-shrink:0}
  .tools .ibtn{min-width:38px;min-height:38px;padding:0 8px}
  .statrow.three{grid-template-columns:repeat(3,1fr)}
  .statrow.three .bigstat{padding:10px 6px}.statrow.three .bigstat b{font-size:1.5rem}
}
@media (max-width:360px){.brand span{display:none}}

.tile.soon-tile{cursor:default;opacity:.85;filter:saturate(.7)}.tile.soon-tile:hover{transform:none;box-shadow:0 18px 30px -20px var(--c1)}.tile.soon-tile:hover .ti{transform:none}.tile.soon-tile .chip{align-self:flex-start;margin-top:6px;background:rgba(255,255,255,.25);color:#fff}

/* ---- showcase (numbers + bullet points) ---- */
.showcase{margin-top:34px}
.sc-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(150px,1fr));gap:14px;margin-top:12px}
.sc-big{background:var(--card,#fff);border:1px solid var(--line,rgba(0,0,0,.08));border-top:6px solid var(--c);border-radius:20px;padding:16px;text-align:center;transition:transform .18s cubic-bezier(.2,1.4,.4,1)}
.sc-big:hover{transform:translateY(-4px) rotate(-1deg)}
.sc-ic{font-size:1.8rem}.sc-n{font-size:2.3rem;font-weight:900;line-height:1.1;color:var(--c)}.sc-l{font-size:.9rem;opacity:.8;font-weight:700}
.sc-list{list-style:none;margin:18px 0 0;padding:0;display:grid;grid-template-columns:repeat(auto-fit,minmax(280px,1fr));gap:10px}
.sc-list li{display:flex;gap:12px;align-items:flex-start;padding:12px 14px;border-radius:16px;background:var(--card,#fff);border:1px solid var(--line,rgba(0,0,0,.08))}
.sc-list li>span{font-size:1.4rem;line-height:1.2}
.sc-strip{display:flex;flex-wrap:wrap;justify-content:center;gap:10px;max-width:900px;margin:0 auto;padding:0 16px}
.sc-chip{display:flex;align-items:baseline;gap:6px;padding:8px 14px;border-radius:999px;background:var(--card,#fff);border:1px solid var(--line,rgba(0,0,0,.1));font-size:.92rem}
.sc-chip b{font-size:1.15rem;color:var(--brand,#5B4BFF)}
@media (max-width:600px){.sc-grid{grid-template-columns:repeat(2,1fr)}.sc-list{grid-template-columns:1fr}}