:root{
  --bg:#05060f; --bg2:#0a0b1e; --panel:rgba(255,255,255,.045); --panel2:rgba(255,255,255,.07);
  --line:rgba(255,255,255,.10); --tx:#eef1ff; --mut:#aeb6d8; --brand:#7c5cff; --brand2:#00e0c6;
  --acc:#ff5c8a; --ok:#38e08b; --r:18px; --sh:0 8px 40px rgba(0,0,0,.45);
  --ff:'Inter',system-ui,-apple-system,Segoe UI,Roboto,Helvetica,Arial,sans-serif;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{margin:0;font-family:var(--ff);color:var(--tx);line-height:1.65;
  background:
    radial-gradient(60vw 60vw at 12% -8%,rgba(124,92,255,.28),transparent 60%),
    radial-gradient(50vw 50vw at 100% 0%,rgba(0,224,198,.20),transparent 55%),
    radial-gradient(60vw 60vw at 50% 120%,rgba(255,92,138,.16),transparent 60%),
    var(--bg);
  min-height:100vh;overflow-x:hidden}
a{color:var(--brand2);text-decoration:none}
a:hover{text-decoration:underline}
.wrap{max-width:1120px;margin:0 auto;padding:0 20px}
h1,h2,h3{line-height:1.2;letter-spacing:-.02em;margin:0 0 .5em}
h1{font-size:clamp(1.7rem,4.5vw,2.6rem);font-weight:800}
h2{font-size:clamp(1.25rem,3vw,1.7rem);font-weight:700;margin-top:0}
.muted{color:var(--mut)}

/* header */
.hd{position:sticky;top:0;z-index:50;backdrop-filter:blur(14px);
  background:rgba(5,6,15,.72);border-bottom:1px solid var(--line)}
.hd-in{display:flex;align-items:center;gap:14px;height:62px}
.brand{display:flex;align-items:center;gap:9px;font-weight:800;color:var(--tx);font-size:1.12rem;letter-spacing:-.02em}
.brand:hover{text-decoration:none}
.brand-mark{display:grid;place-items:center;width:32px;height:32px;border-radius:10px;
  background:linear-gradient(135deg,var(--brand),var(--brand2));color:#fff;font-size:1.1rem;box-shadow:0 4px 18px rgba(124,92,255,.5)}
.nav{margin-left:auto;display:flex;gap:4px;flex-wrap:wrap}
.nav a{color:var(--mut);padding:7px 11px;border-radius:10px;font-size:.9rem;font-weight:500;transition:.15s}
.nav a:hover{color:var(--tx);background:var(--panel);text-decoration:none}
.nav a[aria-current=page]{color:#fff;background:linear-gradient(135deg,rgba(124,92,255,.4),rgba(0,224,198,.25));}
.navtog{display:none;margin-left:auto;background:var(--panel);border:1px solid var(--line);color:var(--tx);
  font-size:1.3rem;width:42px;height:42px;border-radius:11px;cursor:pointer}

.crumb{padding:18px 20px 0;font-size:.85rem;color:var(--mut);max-width:1120px;margin:0 auto}
.crumb a{color:var(--mut)}
.crumb span[aria-current]{color:var(--tx)}

main{padding:26px 0 20px}
.hero{text-align:center;padding:48px 20px 22px;max-width:820px;margin:0 auto}
.hero p{font-size:1.08rem;color:var(--mut);max-width:620px;margin:.6em auto 0}
.pill{display:inline-block;font-size:.78rem;font-weight:600;letter-spacing:.04em;text-transform:uppercase;
  color:var(--brand2);background:var(--panel);border:1px solid var(--line);padding:5px 13px;border-radius:100px;margin-bottom:16px}

/* generic card grid */
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(240px,1fr));gap:16px}
.card{display:flex;flex-direction:column;gap:6px;padding:20px;border-radius:var(--r);
  background:var(--panel);border:1px solid var(--line);transition:.18s;position:relative;overflow:hidden}
.card:hover{transform:translateY(-3px);background:var(--panel2);border-color:rgba(124,92,255,.5);text-decoration:none;box-shadow:var(--sh)}
.card .ci{font-size:1.7rem;line-height:1}
.card .ct{font-weight:700;color:var(--tx);font-size:1.05rem}
.card .cd{font-size:.86rem;color:var(--mut)}

/* tool panel */
.tool{background:var(--panel);border:1px solid var(--line);border-radius:var(--r);padding:24px;margin:22px 0;box-shadow:var(--sh)}
.tool h2{margin-top:0}
.row{display:flex;flex-wrap:wrap;gap:14px;margin-bottom:14px}
.field{flex:1 1 180px;min-width:0;display:flex;flex-direction:column;gap:6px}
.field label{font-size:.85rem;font-weight:600;color:var(--mut)}
input,select,textarea{width:100%;background:rgba(0,0,0,.35);border:1px solid var(--line);color:var(--tx);
  padding:12px 14px;border-radius:12px;font-size:1rem;font-family:inherit;transition:.15s}
input:focus,select:focus,textarea:focus{outline:none;border-color:var(--brand);box-shadow:0 0 0 3px rgba(124,92,255,.25)}
select option{background:#12132a;color:var(--tx)}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;cursor:pointer;border:none;
  background:linear-gradient(135deg,var(--brand),var(--brand2));color:#fff;font-weight:700;font-size:1rem;
  padding:13px 24px;border-radius:12px;transition:.15s;box-shadow:0 6px 22px rgba(124,92,255,.4)}
.btn:hover{filter:brightness(1.08);transform:translateY(-1px)}
.btn.sec{background:var(--panel2);color:var(--tx);border:1px solid var(--line);box-shadow:none}
.btnrow{display:flex;gap:10px;flex-wrap:wrap}

/* result box */
.res{margin-top:18px;padding:18px 20px;border-radius:14px;background:linear-gradient(135deg,rgba(124,92,255,.14),rgba(0,224,198,.08));
  border:1px solid rgba(124,92,255,.35);display:none}
.res.show{display:block;animation:pop .25s ease}
@keyframes pop{from{opacity:0;transform:translateY(6px)}to{opacity:1;transform:none}}
.res .big{font-size:1.9rem;font-weight:800;letter-spacing:-.02em}
.res .big small{font-size:.9rem;font-weight:500;color:var(--mut)}
.res-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(120px,1fr));gap:10px;margin-top:12px}
.res-grid .kv{background:rgba(0,0,0,.25);padding:10px 12px;border-radius:10px}
.res-grid .kv b{display:block;font-size:1.35rem;line-height:1.1}
.res-grid .kv span{font-size:.78rem;color:var(--mut)}

/* scientific calc keypad */
.calcbox{max-width:420px;margin:0 auto}
.calc-disp{background:rgba(0,0,0,.5);border:1px solid var(--line);border-radius:14px;padding:16px;text-align:right;margin-bottom:12px}
.calc-disp .expr{font-size:.9rem;color:var(--mut);min-height:20px;word-break:break-all}
.calc-disp .out{font-size:2rem;font-weight:800;word-break:break-all}
.keys{display:grid;grid-template-columns:repeat(5,1fr);gap:8px}
.keys button{padding:15px 0;font-size:1.05rem;font-weight:600;border-radius:12px;border:1px solid var(--line);
  background:var(--panel2);color:var(--tx);cursor:pointer;transition:.12s}
.keys button:hover{background:rgba(124,92,255,.3)}
.keys .op{color:var(--brand2)}
.keys .eq{background:linear-gradient(135deg,var(--brand),var(--brand2));color:#fff;grid-column:span 2}
.keys .fn{font-size:.85rem;color:var(--mut)}
.keys .clr{color:var(--acc)}

/* article / SEO prose */
.article{max-width:820px;margin:34px auto}
.article h2{margin-top:1.6em}
.article h3{margin-top:1.3em;font-size:1.12rem}
.article p,.article li{color:#cfd4ee}
.article ul,.article ol{padding-left:22px}
.keytakeaway{background:var(--panel);border-left:3px solid var(--brand);border-radius:0 12px 12px 0;padding:14px 18px;margin:18px 0}
table.tb{width:100%;border-collapse:collapse;margin:14px 0;font-size:.92rem}
table.tb th,table.tb td{text-align:left;padding:10px 12px;border-bottom:1px solid var(--line)}
table.tb th{color:var(--brand2);font-weight:600}

/* FAQ */
.faq{max-width:820px;margin:34px auto}
.faq details{background:var(--panel);border:1px solid var(--line);border-radius:12px;margin-bottom:10px;overflow:hidden}
.faq summary{padding:15px 18px;cursor:pointer;font-weight:600;list-style:none;position:relative}
.faq summary::-webkit-details-marker{display:none}
.faq summary::after{content:'+';position:absolute;right:18px;color:var(--brand2);font-size:1.3rem;line-height:1}
.faq details[open] summary::after{content:'\2212'}
.faq .faq-a{padding:0 18px 16px;color:#cfd4ee}

.related{margin:40px auto;max-width:1120px}

/* footer */
.ft{margin-top:50px;border-top:1px solid var(--line);background:rgba(5,6,15,.6);padding:38px 0 26px}
.ft-grid{display:grid;grid-template-columns:1.6fr 1fr 1fr;gap:26px;margin-bottom:22px}
.ft-grid ul{list-style:none;padding:0;margin:0}
.ft-grid li{margin-bottom:7px}
.ft-grid a{color:var(--mut);font-size:.9rem}
.ft-grid strong{display:block;margin-bottom:12px;color:var(--tx)}
.copy{color:var(--mut);font-size:.82rem;border-top:1px solid var(--line);padding-top:18px;margin:0}

@media(max-width:760px){
  .navtog{display:block}
  .nav{position:absolute;top:62px;left:0;right:0;flex-direction:column;gap:2px;padding:12px 20px;
    background:rgba(8,9,22,.98);backdrop-filter:blur(14px);border-bottom:1px solid var(--line);display:none}
  .nav.open{display:flex}
  .nav a{padding:12px;width:100%}
  .ft-grid{grid-template-columns:1fr;gap:18px}
  .hero{padding:32px 16px 12px}
}