:root{--bg:#f6f7fb;--card:#fff;--ink:#0f172a;--muted:#5b6478;--line:#e4e7ef;--brand:#4f46e5;--brand2:#06b6d4;--accent:#10b981;--warn:#f59e0b;--radius:16px;--shadow:0 10px 30px -12px rgba(15,23,42,.18);--fin:#4f46e5;--fit:#10b981;--math:#f59e0b;--oth:#ec4899}
@media (prefers-color-scheme:dark){:root{--bg:#0b1020;--card:#121a2f;--ink:#e8ecf6;--muted:#9aa4bd;--line:#223053;--shadow:0 10px 30px -12px rgba(0,0,0,.6)}}
*{box-sizing:border-box}html{-webkit-text-size-adjust:100%}
body{margin:0;font:16px/1.6 system-ui,-apple-system,"Segoe UI",Roboto,Inter,Arial,sans-serif;background:var(--bg);color:var(--ink)}
a{color:var(--brand);text-decoration:none}a:hover{text-decoration:underline}
img,svg{max-width:100%}
.wrap{max-width:1140px;margin:0 auto;padding:0 18px}
header.top{position:sticky;top:0;z-index:20;background:rgba(255,255,255,.82);backdrop-filter:saturate(1.4) blur(10px);border-bottom:1px solid var(--line)}
@media (prefers-color-scheme:dark){header.top{background:rgba(11,16,32,.82)}}
header.top .wrap{display:flex;align-items:center;gap:16px;height:62px}
.logo{display:flex;align-items:center;gap:10px;font-weight:800;font-size:1.15rem;color:var(--ink)}
.logo:hover{text-decoration:none}
.logo .mark{width:34px;height:34px;border-radius:10px;background:linear-gradient(135deg,var(--brand),var(--brand2));display:grid;place-items:center;color:#fff;font-size:1rem}
.logo b{background:linear-gradient(90deg,var(--brand),var(--brand2));-webkit-background-clip:text;background-clip:text;color:transparent}
nav.main{margin-left:auto;display:flex;gap:4px}
nav.main a{color:var(--muted);padding:8px 12px;border-radius:10px;font-weight:600;font-size:.93rem}
nav.main a:hover{background:var(--line);color:var(--ink);text-decoration:none}
@media (max-width:760px){header.top .wrap{height:auto;flex-wrap:wrap;padding-top:10px;padding-bottom:6px;row-gap:4px}nav.main{margin-left:0;width:100%;overflow-x:auto;white-space:nowrap;-webkit-overflow-scrolling:touch}nav.main a{padding:6px 10px;font-size:.88rem}}
@media (max-width:420px){.fields{grid-template-columns:minmax(0,1fr)}}
.hero{background:radial-gradient(1200px 400px at 10% -10%,rgba(79,70,229,.35),transparent),radial-gradient(900px 400px at 100% 0,rgba(6,182,212,.3),transparent),linear-gradient(180deg,#111a3a,#1b2556);color:#fff;padding:38px 0 46px}
.hero .wrap{display:grid;grid-template-columns:minmax(0,1.05fr) minmax(0,1fr);gap:36px;align-items:center}
@media (max-width:900px){.hero .wrap{grid-template-columns:1fr}.hero .intro{order:-1}}
.hero h1{font-size:clamp(1.8rem,4vw,2.8rem);line-height:1.15;margin:0 0 12px;letter-spacing:-.02em}
.hero p.lead{color:#c9d2ee;font-size:1.08rem;margin:0 0 20px}
.search{position:relative}
.search input{width:100%;padding:15px 18px 15px 46px;border-radius:14px;border:1px solid rgba(255,255,255,.18);background:rgba(255,255,255,.1);color:#fff;font-size:1rem;outline:none}
.search input::placeholder{color:#aab4d4}
.search input:focus{border-color:var(--brand2);background:rgba(255,255,255,.16)}
.search svg{position:absolute;left:15px;top:50%;transform:translateY(-50%);opacity:.7}
.search .results{position:absolute;left:0;right:0;top:calc(100% + 6px);background:var(--card);color:var(--ink);border-radius:14px;box-shadow:var(--shadow);overflow:hidden;display:none;z-index:30;border:1px solid var(--line)}
.search .results a{display:block;padding:11px 16px;color:var(--ink);border-bottom:1px solid var(--line)}
.search .results a:hover,.search .results a.sel{background:var(--line);text-decoration:none}
.chips{display:flex;flex-wrap:wrap;gap:8px;margin-top:16px}
.chips a{background:rgba(255,255,255,.1);border:1px solid rgba(255,255,255,.16);color:#e3e8f8;padding:6px 12px;border-radius:999px;font-size:.88rem}
.chips a:hover{background:rgba(255,255,255,.2);text-decoration:none}
/* scientific calculator */
.sci{background:#0d142c;border:1px solid rgba(255,255,255,.12);border-radius:22px;padding:16px;box-shadow:0 30px 60px -20px rgba(0,0,0,.6)}
.sci .disp{background:linear-gradient(180deg,#0a1024,#111b3d);border-radius:14px;padding:12px 16px;text-align:right;margin-bottom:12px;border:1px solid rgba(255,255,255,.08);min-height:88px;display:flex;flex-direction:column;justify-content:flex-end}
.sci .expr{color:#8f9bc4;font-size:.95rem;min-height:1.4em;word-break:break-all;font-family:ui-monospace,Menlo,Consolas,monospace}
.sci .out{color:#fff;font-size:2rem;font-weight:700;word-break:break-all;font-family:ui-monospace,Menlo,Consolas,monospace;line-height:1.2}
.sci .bar{display:flex;justify-content:space-between;align-items:center;margin-bottom:10px;color:#9aa6cc;font-size:.85rem}
.sci .mode{display:inline-flex;background:rgba(255,255,255,.07);border-radius:999px;padding:3px}
.sci .mode button{background:none;border:0;color:#9aa6cc;padding:4px 12px;border-radius:999px;cursor:pointer;font-weight:700;font-size:.8rem}
.sci .mode button.on{background:var(--brand);color:#fff}
.sci .keys{display:grid;grid-template-columns:repeat(10,1fr);gap:6px}
@media (max-width:560px){.sci .keys{grid-template-columns:repeat(5,1fr)}.sci .keys .fn{order:2}.sci .keys .nm{order:1}}
.sci .keys button{border:0;border-radius:10px;padding:11px 0;font-size:.92rem;font-weight:600;cursor:pointer;background:#1a2547;color:#dfe5fb;transition:transform .06s,background .15s;font-family:inherit}
.sci .keys button:hover{background:#243260}.sci .keys button:active{transform:scale(.96)}
.sci .keys button.nm{background:#2a3870;color:#fff;font-size:1.02rem}
.sci .keys button.op{background:#36407f;color:#c7d2ff}
.sci .keys button.eq{background:linear-gradient(135deg,var(--brand),var(--brand2));color:#fff}
.sci .keys button.ac{background:#7f1d1d;color:#fecaca}
.sci sup{font-size:.65em}
/* sections */
section{padding:44px 0}
h2.sec{font-size:1.6rem;margin:0 0 6px;letter-spacing:-.01em}
p.sub{color:var(--muted);margin:0 0 24px}
.cats{display:grid;grid-template-columns:repeat(4,1fr);gap:18px}
@media (max-width:1000px){.cats{grid-template-columns:repeat(2,1fr)}}
@media (max-width:560px){.cats{grid-template-columns:1fr}}
.cat{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:20px;box-shadow:var(--shadow);position:relative;overflow:hidden}
.cat:before{content:"";position:absolute;inset:0 0 auto 0;height:4px;background:var(--c)}
.cat .ic{width:46px;height:46px;border-radius:12px;display:grid;place-items:center;background:color-mix(in srgb,var(--c) 14%,transparent);color:var(--c);margin-bottom:12px}
.cat h3{margin:0 0 10px;font-size:1.12rem}
.cat ul{list-style:none;margin:0;padding:0}
.cat li a{display:flex;justify-content:space-between;padding:7px 0;border-bottom:1px dashed var(--line);color:var(--ink);font-size:.96rem}
.cat li:last-child a{border-bottom:0}
.cat li a:after{content:"→";color:var(--muted);transition:transform .15s}
.cat li a:hover{color:var(--c);text-decoration:none}.cat li a:hover:after{transform:translateX(3px);color:var(--c)}
.grid3{display:grid;grid-template-columns:repeat(3,1fr);gap:18px}
@media (max-width:860px){.grid3{grid-template-columns:1fr}}
.feat{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:20px}
.feat h3{margin:.2rem 0 .4rem;font-size:1.05rem}.feat p{margin:0;color:var(--muted)}
/* calculator page */
.crumbs{font-size:.88rem;color:var(--muted);padding:16px 0 0}
.crumbs a{color:var(--muted)}
.page-h{padding:8px 0 18px}
.page-h h1{margin:6px 0 6px;font-size:clamp(1.6rem,3.4vw,2.3rem);letter-spacing:-.02em}
.page-h p{color:var(--muted);margin:0;max-width:760px}
.calc-layout{display:grid;grid-template-columns:minmax(0,1fr) 300px;gap:26px;align-items:start}
@media (max-width:980px){.calc-layout{grid-template-columns:1fr}}
.panel{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);box-shadow:var(--shadow);padding:22px}
.calc-box{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:22px}
@media (max-width:700px){.calc-box{grid-template-columns:1fr}}
.fields{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:12px 14px;align-content:start}
.field{display:flex;flex-direction:column;gap:5px;min-width:0}
*{box-sizing:border-box}
.field.full{grid-column:1/-1}
.field label{font-size:.85rem;font-weight:600;color:var(--muted)}
.field input,.field select,.field textarea{width:100%;padding:11px 12px;border-radius:11px;border:1px solid var(--line);background:var(--bg);color:var(--ink);font:inherit;font-size:1rem;outline:none}
.field textarea{min-height:110px;resize:vertical}
.field input:focus,.field select:focus,.field textarea:focus{border-color:var(--brand);box-shadow:0 0 0 3px color-mix(in srgb,var(--brand) 20%,transparent)}
.field .unit{position:relative}.field .unit span{position:absolute;right:12px;top:50%;transform:translateY(-50%);color:var(--muted);font-size:.85rem;pointer-events:none}
.field.check{flex-direction:row;align-items:center;gap:8px}.field.check input{width:auto}
.field.check label{font-size:.95rem;color:var(--ink);font-weight:500}
.btns{grid-column:1/-1;display:flex;gap:10px;margin-top:4px}
.btn{border:0;border-radius:11px;padding:12px 20px;font-weight:700;font:inherit;font-weight:700;cursor:pointer;background:linear-gradient(135deg,var(--brand),var(--brand2));color:#fff}
.btn.ghost{background:var(--line);color:var(--ink)}
.result{background:linear-gradient(160deg,color-mix(in srgb,var(--brand) 10%,var(--card)),var(--card));border:1px solid color-mix(in srgb,var(--brand) 30%,var(--line));border-radius:14px;padding:18px}
.result .lbl{font-size:.82rem;text-transform:uppercase;letter-spacing:.06em;color:var(--muted);font-weight:700}
.result .main{font-size:2rem;font-weight:800;line-height:1.2;margin:4px 0 4px;word-break:break-word;background:linear-gradient(90deg,var(--brand),var(--brand2));-webkit-background-clip:text;background-clip:text;color:transparent}
.result .note{color:var(--muted);font-size:.92rem;margin-bottom:8px}
.result .err{color:#dc2626;font-weight:600}
.kv{width:100%;border-collapse:collapse;font-size:.95rem}
.kv td{padding:7px 0;border-bottom:1px solid var(--line)}.kv td:last-child{text-align:right;font-weight:700}
.kv tr:last-child td{border-bottom:0}
.tbl-wrap{overflow:auto;margin-top:18px;max-height:420px;border:1px solid var(--line);border-radius:12px}
table.data{width:100%;border-collapse:collapse;font-size:.9rem}
table.data th,table.data td{padding:8px 12px;text-align:right;border-bottom:1px solid var(--line);white-space:nowrap}
table.data th:first-child,table.data td:first-child{text-align:left}
table.data th{position:sticky;top:0;background:var(--card);font-size:.8rem;text-transform:uppercase;color:var(--muted)}
.bar-viz{height:12px;border-radius:999px;overflow:hidden;display:flex;margin:10px 0 4px;background:var(--line)}
.bar-viz i{display:block;height:100%}
.legend{display:flex;gap:14px;flex-wrap:wrap;font-size:.82rem;color:var(--muted)}
.legend b{display:inline-block;width:10px;height:10px;border-radius:3px;margin-right:5px;vertical-align:middle}
.copy{margin-top:10px}
article.content{margin-top:26px}
article.content h2{font-size:1.35rem;margin:1.6em 0 .5em;letter-spacing:-.01em}
article.content h3{font-size:1.08rem;margin:1.2em 0 .4em}
article.content p,article.content li{color:color-mix(in srgb,var(--ink) 88%,var(--muted))}
.formula{background:var(--bg);border:1px solid var(--line);border-radius:12px;padding:12px 16px;font-family:ui-monospace,Menlo,Consolas,monospace;font-size:.92rem;overflow:auto}
details.faq{border:1px solid var(--line);border-radius:12px;padding:0 16px;margin:10px 0;background:var(--card)}
details.faq summary{cursor:pointer;font-weight:700;padding:14px 0;list-style:none}
details.faq summary::-webkit-details-marker{display:none}
details.faq summary:after{content:"+";float:right;color:var(--brand);font-size:1.2rem;line-height:1}
details.faq[open] summary:after{content:"–"}
details.faq p{margin:0 0 14px}
aside .panel{padding:18px}
aside h3{margin:0 0 10px;font-size:1rem}
aside ul{list-style:none;padding:0;margin:0}
aside li a{display:block;padding:6px 0;color:var(--ink);font-size:.94rem;border-bottom:1px solid var(--line)}
aside li:last-child a{border-bottom:0}
aside .sticky{position:sticky;top:80px;display:grid;gap:18px}
.prose{max-width:820px}
.prose h1{font-size:2rem;letter-spacing:-.02em}
.prose h2{font-size:1.3rem;margin-top:1.6em}
footer.site{margin-top:50px;background:#0b1020;color:#aab4d4;padding:38px 0 26px;font-size:.93rem}
footer.site .cols{display:grid;grid-template-columns:2fr 1fr 1fr 1fr;gap:24px}
@media (max-width:760px){footer.site .cols{grid-template-columns:1fr 1fr}}
footer.site h4{color:#fff;margin:0 0 10px;font-size:.95rem}
footer.site a{color:#aab4d4;display:block;padding:3px 0}
footer.site a:hover{color:#fff}
footer.site .legal{border-top:1px solid #1e2a4a;margin-top:26px;padding-top:16px;display:flex;justify-content:space-between;flex-wrap:wrap;gap:10px}
#cc{position:fixed;left:16px;right:16px;bottom:16px;max-width:620px;margin:0 auto;background:var(--card);color:var(--ink);border:1px solid var(--line);border-radius:16px;box-shadow:0 20px 50px -10px rgba(0,0,0,.35);padding:18px;z-index:100;display:none}
#cc p{margin:0 0 12px;font-size:.93rem}
#cc .row{display:flex;gap:10px;flex-wrap:wrap}
.contact-form{display:grid;gap:12px;max-width:560px}
.ok{background:#dcfce7;color:#14532d;border-radius:12px;padding:12px 16px}
.pw{font-family:ui-monospace,Menlo,Consolas,monospace;font-size:1.25rem;word-break:break-all;-webkit-text-fill-color:currentColor;color:var(--ink);background:none}
.calc-layout>*,.calc-box>*{min-width:0}.tbl-wrap{overflow-x:auto;max-width:100%}