/* ui.css: sidebar shell, navigation, search, math fields, demos, lesson checks, polish */
:root{--side:272px}
body{display:flex;min-height:100vh;background-attachment:fixed}
.top{display:none}

/* ---------- sidebar ---------- */
#side{position:sticky;top:0;align-self:flex-start;flex:none;width:var(--side);height:100vh;display:flex;flex-direction:column;gap:12px;padding:16px 12px 12px;background:linear-gradient(180deg,#0c1329,#0a1021);border-right:1px solid var(--line);z-index:30}
#side .logo{padding:2px 8px 4px}
.sbtn{display:flex;align-items:center;justify-content:space-between;gap:8px;margin:0 4px;padding:9px 12px;background:var(--panel);border:1px solid var(--line);border-radius:11px;color:var(--mute);font-size:.88rem;text-align:left}
.sbtn:hover{border-color:var(--cy);color:var(--text)}
kbd{font:600 .7rem Consolas,monospace;padding:2px 6px;border:1px solid var(--line);border-bottom-width:2px;border-radius:5px;background:#0b1122;color:var(--mute)}
#side #nav{display:flex;flex-direction:column;gap:1px;flex:1;overflow-y:auto;overflow-x:hidden;padding:0 2px 8px;scrollbar-width:thin;scrollbar-color:var(--line) transparent}
#side #nav a{display:flex;align-items:center;gap:10px;padding:7px 10px;border-radius:9px;color:#b4bfdc;font-size:.9rem;line-height:1.25;white-space:normal;border-left:3px solid transparent}
#side #nav a:hover{background:var(--panel);color:var(--text)}
#side #nav a.on{background:var(--panel2);color:var(--text);font-weight:600;border-left-color:var(--c,var(--cy));border-radius:4px 9px 9px 4px}
#nav .ni{width:22px;text-align:center;flex:none;font-size:1rem}
#nav .nt{flex:1;min-width:0}
#nav .nt b{display:inline-grid;place-items:center;width:20px;height:20px;border-radius:6px;background:color-mix(in srgb,var(--c) 22%,transparent);color:var(--c);font-size:.72rem;margin-right:7px}
#nav .npct{font-size:.7rem;color:var(--mute);font-variant-numeric:tabular-nums}
#nav .npct.full{color:var(--green)}
#nav .nbadge{font-size:.7rem;background:var(--pink);color:#2a0010;font-weight:700;border-radius:99px;padding:1px 7px}
.ngroup{font-size:.68rem;letter-spacing:.16em;text-transform:uppercase;color:#6d7aa3;margin:14px 10px 4px;font-weight:600}
#side .hud{display:block;padding:10px 12px;border:1px solid var(--line);border-radius:12px;background:var(--panel)}
#side .lvrow{margin-bottom:6px;font-size:.85rem}

/* ---------- main column + top bar ---------- */
#main{flex:1;min-width:0;display:flex;flex-direction:column}
.topbar{position:sticky;top:0;z-index:20;display:flex;align-items:center;gap:12px;padding:10px 28px;background:rgba(8,13,28,.88);backdrop-filter:blur(10px);border-bottom:1px solid var(--line);min-height:52px}
#crumbs{flex:1;min-width:0;display:flex;align-items:center;gap:8px;font-size:.88rem;color:var(--mute);overflow:hidden;white-space:nowrap}
#crumbs a{color:var(--mute)}#crumbs a:hover{color:var(--cy)}
#crumbs span.sep{opacity:.5}#crumbs b{color:var(--text);font-weight:600;overflow:hidden;text-overflow:ellipsis}
.tbtn,#menu{background:var(--panel);border:1px solid var(--line);border-radius:10px;width:36px;height:36px;display:grid;place-items:center;color:var(--text);font-size:1rem}
.tbtn:hover,#menu:hover{border-color:var(--cy)}
#menu{display:none}.tbtn{display:none}
#streak{font-weight:700;color:var(--gold);white-space:nowrap;padding:5px 11px;border:1px solid var(--line);border-radius:99px;background:var(--panel);font-size:.9rem}
#app{width:100%;max-width:1120px;margin:0 auto;padding:30px 28px 90px}
#scrim{display:none}

/* ---------- search palette ---------- */
#pal{position:fixed;inset:0;z-index:100;background:rgba(3,6,16,.7);backdrop-filter:blur(5px);display:flex;justify-content:center;align-items:flex-start;padding:12vh 16px 0}
#pal[hidden]{display:none}
.palbox{width:min(640px,100%);background:var(--panel);border:1px solid var(--cy);border-radius:16px;box-shadow:0 30px 80px rgba(0,0,0,.7);overflow:hidden}
#palq{width:100%;padding:16px 20px;background:transparent;border:0;border-bottom:1px solid var(--line);color:var(--text);font:1.1rem inherit;outline:none}
#palr{max-height:min(52vh,420px);overflow-y:auto;padding:6px}
.pr{display:flex;align-items:center;gap:12px;padding:10px 14px;border-radius:10px;color:var(--text);cursor:pointer}
.pr.sel,.pr:hover{background:var(--panel2)}
.pr .pi{width:30px;height:30px;border-radius:8px;display:grid;place-items:center;background:color-mix(in srgb,var(--c,var(--cy)) 20%,transparent);color:var(--c,var(--cy));font-size:.8rem;font-weight:700;flex:none}
.pr b{display:block;font-size:.95rem;font-weight:600}.pr small{color:var(--mute);font-size:.8rem}
.pnone{padding:22px;text-align:center;color:var(--mute)}
.palh{display:flex;gap:10px;align-items:center;padding:8px 16px;border-top:1px solid var(--line);color:var(--mute);font-size:.78rem}

/* ---------- math fields ---------- */
.mfprev{min-height:2.7rem;margin-top:6px;padding:6px 14px;background:#0b1122;border:1px dashed var(--line);border-radius:10px;overflow-x:auto;display:flex;align-items:center;color:var(--text);font-size:1.12rem;transition:opacity .15s}
.mfprev:empty{opacity:.35}.mfprev:empty::before{content:"your math appears here";font-size:.8rem;color:var(--mute);font-style:italic}
.mfprev.stale{opacity:.45}
.mfpad{display:grid;grid-template-columns:repeat(6,1fr);gap:5px;margin-top:8px;padding:8px;background:var(--panel2);border:1px solid var(--line);border-radius:12px;max-width:430px}
.mfpad[hidden]{display:none}
.mfpad button{padding:7px 0;background:#0b1122;border:1px solid var(--line);border-radius:8px;color:var(--text);font:600 .92rem "Segoe UI",system-ui,sans-serif;min-height:34px}
.mfpad button:hover{border-color:var(--cy);background:rgba(92,225,230,.1)}
.mfpad button:active{transform:scale(.94)}
.mfpad button[data-v="BK"]{color:var(--pink)}
.inwrap{max-width:460px}
.fld input.mf{width:100%}

/* ---------- mode switch ---------- */
.mode{display:inline-flex;border:1px solid var(--line);border-radius:10px;overflow:hidden;background:var(--panel)}
.mode button{padding:7px 14px;background:transparent;border:0;color:var(--mute);font-size:.86rem;font-weight:600}
.mode button.on{background:var(--cy);color:#06202a}
.mode button:not(.on):hover{color:var(--text)}
.modebar{display:flex;align-items:center;gap:12px;flex-wrap:wrap;color:var(--mute);font-size:.86rem}

/* ---------- lesson page ---------- */
.uhead{border:1px solid var(--line);border-radius:20px;padding:22px 26px;margin-bottom:22px;background:radial-gradient(700px 200px at 0 0,color-mix(in srgb,var(--c) 18%,transparent),transparent 70%),var(--panel)}
.uhead h1{margin-top:4px}
.uhead .uacts{margin-top:4px}
.uprog{display:flex;align-items:center;gap:14px;margin-top:14px;color:var(--mute);font-size:.85rem}.uprog .bar{flex:1;max-width:340px}
.ulayout{grid-template-columns:270px minmax(0,1fr)}
.slist{top:68px;max-height:calc(100vh - 84px);overflow-y:auto}
.notes{padding:34px 40px}
.notes>.ntop h2{font-size:1.9rem}
.pills{display:flex;gap:8px;flex-wrap:wrap;margin:-6px 0 18px}
.pill2{display:inline-flex;align-items:center;gap:6px;padding:4px 12px;border:1px solid var(--line);border-radius:99px;font-size:.82rem;color:var(--mute);background:var(--panel2)}
a.pill2:hover{border-color:var(--cy);color:var(--cy)}
.notes h4{display:flex;align-items:center;gap:8px}.notes h4::before{content:"";width:6px;height:6px;border-radius:50%;background:var(--c)}

/* demos */
.demo{margin:30px 0 8px;border:1px solid var(--c,var(--cy));border-radius:16px;overflow:hidden;background:linear-gradient(180deg,rgba(92,225,230,.05),transparent),var(--panel2)}
.dhead{display:flex;align-items:center;gap:12px;padding:11px 18px;border-bottom:1px solid var(--line);background:rgba(8,13,28,.45)}
.dhead span{font-size:.66rem;letter-spacing:.16em;font-weight:700;color:#06202a;background:var(--c,var(--cy));border-radius:6px;padding:3px 8px}
.dhead b{font-size:1rem}
.dbody{display:grid;grid-template-columns:minmax(0,320px) minmax(0,1fr);gap:18px;padding:18px}
.dctl{display:flex;flex-direction:column;gap:12px;min-width:0}
.democv{display:block;width:100%;aspect-ratio:16/11;border:1px solid var(--line);border-radius:12px;touch-action:none;cursor:grab;align-self:start}
.dread{grid-template-columns:1fr;margin:0}.dread .rd{padding:6px 12px}
.demo select{padding:8px 10px;background:#0b1122;border:1.5px solid var(--line);border-radius:9px;color:var(--text);font:.95rem Consolas,monospace}

/* lesson check card */
.lcheck{margin:34px 0 4px;border:1px solid var(--line);border-radius:16px;background:var(--panel2);overflow:hidden}
.lchead{display:flex;align-items:center;gap:12px;flex-wrap:wrap;padding:13px 20px;border-bottom:1px solid var(--line);background:rgba(8,13,28,.45)}
.lchead h3{font-size:1.05rem;flex:1;min-width:140px}
.lcscore{font:600 .85rem Consolas,monospace;color:var(--mute)}
.lcbody{padding:20px 22px}
.lcbody .qtext{font-size:1.06rem}
.lcact{display:flex;gap:10px;justify-content:flex-end;margin-top:16px}
.lcdots{display:flex;gap:5px;margin-left:4px}.lcdots i{width:9px;height:9px;border-radius:50%;background:var(--line)}.lcdots i.ok{background:var(--green)}.lcdots i.no{background:var(--red)}

/* ---------- home polish ---------- */
.hero{position:relative;overflow:hidden}
.hero::after{content:"∫";position:absolute;right:-10px;bottom:-60px;font:italic 15rem/1 Georgia,serif;color:rgba(92,225,230,.05);pointer-events:none}
.contin{display:flex;align-items:center;gap:18px;padding:16px 20px;margin:16px 0 0;border:1px solid var(--line);border-radius:16px;background:var(--panel);color:var(--text)}
.contin:hover{border-color:var(--cy)}.contin .ci{font-size:1.6rem}.contin small{display:block;color:var(--mute);font-size:.78rem;letter-spacing:.1em;text-transform:uppercase}.contin b{font-size:1.05rem}
.contin .go{margin-left:auto;color:var(--cy);font-weight:700;white-space:nowrap}
.ucard{position:relative}.ucard::before{content:"";position:absolute;inset:0;border-radius:inherit;background:radial-gradient(260px 120px at 100% 0,color-mix(in srgb,var(--c) 14%,transparent),transparent);pointer-events:none}
.ucard h3{font-size:1.04rem}
.qcard,.notes,.mcard,.frqpart{box-shadow:0 1px 0 rgba(255,255,255,.03) inset,0 10px 30px -18px rgba(0,0,0,.7)}
.btn{box-shadow:0 1px 0 rgba(255,255,255,.25) inset}
.btn.ghost{box-shadow:none}
.choice{transition:transform .1s,border-color .12s,background .12s}.choice:hover:not(:disabled){transform:translateX(3px)}
::selection{background:rgba(92,225,230,.3)}
@supports(scrollbar-color:auto){*{scrollbar-color:var(--line) transparent}}

/* ---------- responsive ---------- */
@media(max-width:1100px){.dbody{grid-template-columns:1fr}}
@media(max-width:900px){
body{display:block}
#side{position:fixed;left:0;top:0;bottom:0;transform:translateX(-102%);transition:transform .25s;box-shadow:20px 0 60px rgba(0,0,0,.6)}
body.menu-open #side{transform:none}
body.menu-open #scrim{display:block;position:fixed;inset:0;background:rgba(3,6,16,.6);z-index:25}
#menu,.tbtn{display:grid}
.topbar{padding:8px 14px}
#app{padding:18px 14px 80px}
.notes{padding:22px 18px}
.slist{position:static;max-height:none}
.ulayout{grid-template-columns:1fr}
.mfpad{grid-template-columns:repeat(6,1fr);max-width:none}
.uhead{padding:18px}
}

/* patch */
.uhead{display:block}
#demo,#lc{scroll-margin-top:70px}
.pill2[data-jump]{cursor:pointer}
.pr .pi{font-size:.85rem}
@media(max-width:700px){.dread{grid-template-columns:1fr 1fr}.dread .rd b{font-size:.9rem}}

/* topics */
.chk{width:auto!important;min-width:30px;height:26px!important;padding:0 7px;border-radius:99px!important;font-size:.72rem!important;font-weight:600;font-variant-numeric:tabular-nums}
.slist{max-height:calc(100vh - 100px)}
.slist a{padding:8px 10px}
.st b{font-size:.88rem}
.tnum{display:inline-block;margin-right:10px;padding:0 12px;border-radius:12px;background:color-mix(in srgb,var(--c) 22%,transparent);color:var(--c);font-size:.62em;vertical-align:.18em;letter-spacing:.02em}
.bcpill{background:#9b6bff;color:#14062e;border-radius:6px;padding:1px 8px;font-size:.72rem;letter-spacing:.06em}

/* hints */
.hints{margin-top:16px;display:flex;flex-direction:column;gap:10px;align-items:flex-start}
.hlist{display:flex;flex-direction:column;gap:10px;width:100%}
.hint{border:1px dashed var(--gold);border-radius:12px;padding:12px 16px;background:rgba(255,200,87,.05);animation:pop .25s}
.hint>b{display:block;font-size:.78rem;letter-spacing:.1em;text-transform:uppercase;color:var(--gold);margin-bottom:6px}
.hint p{margin:4px 0}.hint .k,.hint .x{margin:6px 0 0;font-size:.95rem}
.hbtn{border-color:var(--gold)!important;color:var(--gold)!important}
.hbtn:hover{background:rgba(255,200,87,.1)!important}
.hbtn.last{border-color:var(--pink)!important;color:var(--pink)!important}
.hbtn:disabled{opacity:.35}
.elim{opacity:.32;text-decoration:line-through;pointer-events:none}