/* ==========================================================================
   Calculate — design system (hand-authored, no build step required)
   ========================================================================== */
:root{
  --primary-50:#eef4ff; --primary-100:#dbe6fe; --primary-200:#bfd3fe; --primary-400:#5b8def;
  --primary-500:#3467e6; --primary-600:#2451c9; --primary-700:#1c3fa0; --primary-900:#152c70;
  --accent-500:#0fae7a; --accent-600:#0c8f64;
  --gray-25:#fafbfc; --gray-50:#f6f8fa; --gray-100:#eef1f5; --gray-200:#dfe4ea; --gray-300:#c6ccd6;
  --gray-400:#9aa3b2; --gray-500:#717c8f; --gray-600:#535d6e; --gray-700:#3c4453; --gray-800:#262c38;
  --gray-900:#161a22;
  --danger-500:#e0483f;
  --radius-sm:6px; --radius-md:10px; --radius-lg:16px; --radius-xl:22px;
  --shadow-sm:0 1px 2px rgba(22,26,34,.06);
  --shadow-md:0 4px 16px rgba(22,26,34,.08);
  --shadow-lg:0 12px 32px rgba(22,26,34,.12);
  --font-sans: ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --container: 1180px;
}
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}
body{margin:0;font-family:var(--font-sans);color:var(--gray-800);background:#fff;line-height:1.55;font-size:16px;-webkit-font-smoothing:antialiased}
img,svg{display:block;max-width:100%}
a{color:inherit;text-decoration:none}
h1,h2,h3,h4{line-height:1.2;margin:0 0 .5em;font-weight:700;letter-spacing:-0.01em;color:var(--gray-900)}
h1{font-size:clamp(1.7rem,1.3rem + 1.6vw,2.5rem)}
h2{font-size:clamp(1.35rem,1.15rem + .8vw,1.9rem)}
h3{font-size:1.2rem}
p{margin:0 0 1em}
ul,ol{margin:0 0 1em;padding-left:1.25em}
button,input,select,textarea{font-family:inherit;font-size:1rem}
:focus-visible{outline:3px solid var(--primary-400);outline-offset:2px}

.container{max-width:var(--container);margin:0 auto;padding:0 20px}
.visually-hidden{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}
.skip-link{position:absolute;left:8px;top:-48px;background:var(--primary-600);color:#fff;padding:10px 16px;border-radius:var(--radius-sm);z-index:200;transition:top .15s}
.skip-link:focus{top:8px}

/* ---------- Header ---------- */
.site-header{position:sticky;top:0;z-index:100;background:rgba(255,255,255,.92);backdrop-filter:saturate(180%) blur(8px);border-bottom:1px solid var(--gray-100)}
.site-header .container{display:flex;align-items:center;gap:24px;height:66px}
.logo{display:flex;align-items:center;gap:8px;font-weight:800;font-size:1.2rem;color:var(--gray-900);flex-shrink:0}
.logo .logo-mark{width:30px;height:30px;border-radius:9px;background:linear-gradient(135deg,var(--primary-500),var(--accent-500));display:flex;align-items:center;justify-content:center;color:#fff;font-weight:800;font-size:1rem}
.main-nav{display:none;gap:4px;align-items:center}
.main-nav a{padding:8px 12px;border-radius:var(--radius-sm);font-weight:600;font-size:.94rem;color:var(--gray-700)}
.main-nav a:hover{background:var(--gray-50);color:var(--primary-600)}
@media(min-width:900px){.main-nav{display:flex}}

.header-search{position:relative;flex:1;max-width:420px;margin-left:auto}
.header-search input[type="search"]{width:100%;padding:9px 14px 9px 38px;border:1.5px solid var(--gray-200);border-radius:999px;background:var(--gray-50);transition:border-color .15s,background .15s}
.header-search input[type="search"]:focus{border-color:var(--primary-400);background:#fff}
.header-search svg{position:absolute;left:12px;top:50%;transform:translateY(-50%);width:16px;height:16px;color:var(--gray-400)}
.search-results{position:absolute;top:calc(100% + 8px);left:0;right:0;background:#fff;border:1px solid var(--gray-100);border-radius:var(--radius-md);box-shadow:var(--shadow-lg);max-height:70vh;overflow:auto;display:none;z-index:150}
.search-results.open{display:block}
.search-results a{display:flex;align-items:center;gap:10px;padding:10px 14px;border-bottom:1px solid var(--gray-50)}
.search-results a:last-child{border-bottom:none}
.search-results a:hover,.search-results a.active{background:var(--primary-50)}
.search-results .sr-name{font-weight:600;font-size:.92rem;color:var(--gray-900)}
.search-results .sr-cat{font-size:.76rem;color:var(--gray-500)}
.search-results .sr-icon{width:30px;height:30px;border-radius:8px;background:var(--primary-50);color:var(--primary-600);display:flex;align-items:center;justify-content:center;flex-shrink:0}
.search-results .sr-icon svg{width:16px;height:16px}
.search-empty{padding:16px;color:var(--gray-500);font-size:.9rem;text-align:center}

.mobile-nav-toggle{display:inline-flex;align-items:center;justify-content:center;width:38px;height:38px;border-radius:var(--radius-sm);border:1.5px solid var(--gray-200);background:#fff;flex-shrink:0}
@media(min-width:900px){.mobile-nav-toggle{display:none}}
.mobile-nav{display:none;border-top:1px solid var(--gray-100);padding:12px 20px 18px}
.mobile-nav.open{display:block}
.mobile-nav a{display:block;padding:10px 0;font-weight:600;color:var(--gray-700);border-bottom:1px solid var(--gray-50)}

/* ---------- Hero ---------- */
.hero{padding:56px 0 64px;background:linear-gradient(180deg,var(--primary-50) 0%,#fff 100%)}
.hero .eyebrow{display:inline-flex;align-items:center;gap:6px;background:#fff;border:1px solid var(--gray-200);color:var(--primary-600);font-weight:700;font-size:.78rem;padding:6px 12px;border-radius:999px;margin-bottom:18px}
.hero h1{max-width:760px}
.hero .lede{font-size:1.15rem;color:var(--gray-600);max-width:620px;margin-bottom:28px}
.hero-search{position:relative;max-width:640px}
.hero-search input[type="search"]{width:100%;padding:18px 20px 18px 52px;font-size:1.05rem;border:2px solid var(--gray-200);border-radius:var(--radius-xl);box-shadow:var(--shadow-md);background:#fff}
.hero-search input[type="search"]:focus{border-color:var(--primary-400)}
.hero-search svg.search-icon{position:absolute;left:20px;top:50%;transform:translateY(-50%);width:20px;height:20px;color:var(--gray-400)}
.hero-search .search-results{border-radius:var(--radius-lg)}
.hero-hint{margin-top:12px;font-size:.85rem;color:var(--gray-500)}
.hero-stats{display:flex;gap:28px;margin-top:32px;flex-wrap:wrap}
.hero-stats .stat-num{font-size:1.5rem;font-weight:800;color:var(--gray-900)}
.hero-stats .stat-label{font-size:.8rem;color:var(--gray-500)}

/* ---------- Category cards ---------- */
.section{padding:56px 0}
.section-head{display:flex;align-items:flex-end;justify-content:space-between;gap:16px;margin-bottom:28px;flex-wrap:wrap}
.section-head p{color:var(--gray-500);margin:6px 0 0}
.cat-grid{display:grid;grid-template-columns:1fr;gap:20px}
@media(min-width:700px){.cat-grid{grid-template-columns:repeat(2,1fr)}}
@media(min-width:1100px){.cat-grid{grid-template-columns:repeat(4,1fr)}}
.cat-card{display:flex;flex-direction:column;background:#fff;border:1px solid var(--gray-100);border-radius:var(--radius-lg);padding:24px;box-shadow:var(--shadow-sm);transition:transform .15s,box-shadow .15s,border-color .15s}
.cat-card:hover{transform:translateY(-3px);box-shadow:var(--shadow-md);border-color:var(--primary-200)}
.cat-card-link{display:block}
.cat-card .cat-icon{width:44px;height:44px;border-radius:12px;background:var(--primary-50);color:var(--primary-600);display:flex;align-items:center;justify-content:center;margin-bottom:14px}
.cat-card .cat-icon svg{width:22px;height:22px}
.cat-card h3{margin-bottom:6px;transition:color .15s}
.cat-card-link:hover h3{color:var(--primary-600)}
.cat-card p{color:var(--gray-500);font-size:.92rem;margin-bottom:14px}
.cat-card ul{list-style:none;padding:0;margin:0;display:flex;flex-direction:column;gap:6px}
.cat-card ul li a{font-size:.86rem;color:var(--primary-600);font-weight:600}
.cat-card ul li a:hover{text-decoration:underline}
.cat-card .cat-more{display:block;font-size:.82rem;color:var(--gray-500);font-weight:700;margin-top:14px;padding-top:14px;border-top:1px solid var(--gray-100)}
.cat-card .cat-more:hover{color:var(--primary-600)}

/* ---------- Calculator grid ---------- */
.calc-grid{display:grid;grid-template-columns:1fr;gap:14px}
@media(min-width:640px){.calc-grid{grid-template-columns:repeat(2,1fr)}}
@media(min-width:980px){.calc-grid{grid-template-columns:repeat(3,1fr)}}
.calc-card{display:flex;gap:14px;background:#fff;border:1px solid var(--gray-100);border-radius:var(--radius-md);padding:16px;transition:border-color .15s,box-shadow .15s}
.calc-card:hover{border-color:var(--primary-200);box-shadow:var(--shadow-sm)}
.calc-card .calc-icon{width:38px;height:38px;border-radius:10px;background:var(--gray-50);color:var(--primary-600);display:flex;align-items:center;justify-content:center;flex-shrink:0}
.calc-card .calc-icon svg{width:19px;height:19px}
.calc-card h4{margin:0 0 4px;font-size:.98rem;font-weight:700;color:var(--gray-900)}
.calc-card p{margin:0;font-size:.84rem;color:var(--gray-500)}
.calc-card[hidden]{display:none}

.cat-filter-group{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:24px}
.cat-filter-group button{border:1.5px solid var(--gray-200);background:#fff;padding:8px 16px;border-radius:999px;font-weight:600;font-size:.86rem;color:var(--gray-600);cursor:pointer}
.cat-filter-group button.active{background:var(--primary-600);border-color:var(--primary-600);color:#fff}

/* ---------- Breadcrumb ---------- */
.breadcrumb{padding:16px 0}
.breadcrumb ol{list-style:none;display:flex;flex-wrap:wrap;gap:6px;margin:0;padding:0;font-size:.86rem;color:var(--gray-500)}
.breadcrumb a{color:var(--gray-500);font-weight:600}
.breadcrumb a:hover{color:var(--primary-600)}
.breadcrumb li:not(:last-child)::after{content:"/";margin-left:6px;color:var(--gray-300)}
.breadcrumb li[aria-current]{color:var(--gray-800);font-weight:600}

/* ---------- Calculator tool layout ---------- */
.calc-page-head{padding:8px 0 24px}
.calc-page-head .lede{font-size:1.06rem;color:var(--gray-600);max-width:760px}
.calc-tool{background:var(--gray-25);border:1px solid var(--gray-100);border-radius:var(--radius-lg);padding:24px;margin:24px 0 40px;box-shadow:var(--shadow-sm)}
@media(min-width:640px){.calc-tool{padding:32px}}
.field-grid{display:grid;grid-template-columns:1fr;gap:16px}
@media(min-width:560px){.field-grid.cols-2{grid-template-columns:1fr 1fr}}
@media(min-width:640px){.field-grid.cols-3{grid-template-columns:1fr 1fr 1fr}}
.field{display:flex;flex-direction:column;gap:6px}
.field label{font-size:.86rem;font-weight:700;color:var(--gray-700)}
.field .hint{font-size:.78rem;color:var(--gray-400);font-weight:400}
.field input[type="text"],.field input[type="number"],.field input[type="date"],.field input[type="time"],.field select,.field textarea{
  padding:11px 13px;border:1.5px solid var(--gray-200);border-radius:var(--radius-sm);background:#fff;color:var(--gray-900);width:100%;
}
.field input:focus,.field select:focus,.field textarea:focus{border-color:var(--primary-400)}
.input-suffix-wrap,.input-prefix-wrap{position:relative}
.input-prefix-wrap input{padding-left:26px}
.input-prefix-wrap::before{content:attr(data-prefix);position:absolute;left:12px;top:50%;transform:translateY(-50%);color:var(--gray-400);font-weight:600}
.input-suffix-wrap input{padding-right:34px}
.input-suffix-wrap::after{content:attr(data-suffix);position:absolute;right:12px;top:50%;transform:translateY(-50%);color:var(--gray-400);font-weight:600;font-size:.85rem}
.radio-row{display:flex;gap:16px;flex-wrap:wrap}
.radio-row label{display:flex;align-items:center;gap:6px;font-weight:600;font-size:.9rem;color:var(--gray-700)}
.form-actions{display:flex;gap:12px;margin-top:22px;flex-wrap:wrap}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;padding:12px 26px;border-radius:999px;font-weight:700;font-size:.95rem;border:none;cursor:pointer;transition:transform .1s,box-shadow .15s}
.btn-primary{background:var(--primary-600);color:#fff;box-shadow:var(--shadow-sm)}
.btn-primary:hover{background:var(--primary-700)}
.btn-secondary{background:#fff;color:var(--gray-700);border:1.5px solid var(--gray-200)}
.btn-secondary:hover{border-color:var(--gray-300)}
.btn:active{transform:scale(.98)}

.result-card{margin-top:26px;padding:22px;border-radius:var(--radius-md);background:linear-gradient(135deg,var(--primary-600),var(--primary-700));color:#fff;min-height:64px}
.result-card[hidden]{display:none}
.result-card .result-label{font-size:.8rem;text-transform:uppercase;letter-spacing:.05em;opacity:.8;font-weight:700;margin-bottom:6px}
.result-card .result-value{font-size:2rem;font-weight:800;line-height:1.15}
.result-card .result-sub{margin-top:14px;display:grid;grid-template-columns:repeat(auto-fit,minmax(140px,1fr));gap:12px;font-size:.86rem}
.result-card .result-sub .k{opacity:.75;display:block;font-size:.76rem}
.result-card .result-sub .v{font-weight:700;font-size:1rem}
.result-card.result-neutral{background:#fff;border:1.5px solid var(--gray-200);color:var(--gray-900)}
.result-card.result-neutral .result-label{color:var(--gray-500);opacity:1}
.error-msg{color:var(--danger-500);font-size:.86rem;font-weight:600;margin-top:10px;display:none}
.error-msg.show{display:block}

.data-table{width:100%;border-collapse:collapse;font-size:.86rem;margin-top:16px}
.data-table th,.data-table td{padding:9px 10px;border-bottom:1px solid var(--gray-100);text-align:right}
.data-table th:first-child,.data-table td:first-child{text-align:left}
.data-table thead th{color:var(--gray-500);font-weight:700;font-size:.76rem;text-transform:uppercase}
.table-scroll{max-height:420px;overflow:auto;border:1px solid var(--gray-100);border-radius:var(--radius-sm)}

/* ---------- Content sections ---------- */
.content-section{padding:8px 0 40px}
.content-section h2{margin-top:1.6em}
.content-section h2:first-child{margin-top:0}
.content-section .formula-box{background:var(--gray-50);border:1px solid var(--gray-100);border-radius:var(--radius-md);padding:18px 20px;font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;font-size:.92rem;overflow-x:auto;margin:1em 0}
.content-section .example-box{background:var(--primary-50);border-left:4px solid var(--primary-500);border-radius:0 var(--radius-sm) var(--radius-sm) 0;padding:16px 18px;margin:1em 0}

.related-grid{display:grid;grid-template-columns:1fr;gap:12px}
@media(min-width:640px){.related-grid{grid-template-columns:repeat(2,1fr)}}
@media(min-width:980px){.related-grid{grid-template-columns:repeat(3,1fr)}}

/* ---------- Footer ---------- */
.site-footer{background:var(--gray-900);color:var(--gray-300);padding:48px 0 24px;margin-top:40px}
.footer-grid{display:grid;grid-template-columns:1fr;gap:32px}
@media(min-width:700px){.footer-grid{grid-template-columns:1.4fr repeat(4,1fr)}}
.footer-grid h4{color:#fff;font-size:.82rem;text-transform:uppercase;letter-spacing:.05em;margin-bottom:14px}
.footer-grid ul{list-style:none;padding:0;margin:0;display:flex;flex-direction:column;gap:8px}
.footer-grid a{font-size:.88rem;color:var(--gray-300)}
.footer-grid a:hover{color:#fff}
.footer-brand p{color:var(--gray-400);font-size:.88rem;max-width:280px}
.footer-bottom{border-top:1px solid var(--gray-800);margin-top:36px;padding-top:20px;display:flex;justify-content:space-between;flex-wrap:wrap;gap:10px;font-size:.8rem;color:var(--gray-500)}
.footer-bottom a{color:var(--gray-500)}
.footer-bottom a:hover{color:#fff}

/* ---------- Static pages ---------- */
.prose{max-width:760px}
.prose h2{margin-top:1.6em}

/* ---------- Utilities ---------- */
.badge{display:inline-block;background:var(--accent-500);color:#fff;font-size:.72rem;font-weight:700;padding:3px 9px;border-radius:999px}

/* ---------- Hero two-column layout + calculator widget ---------- */
.hero-grid{display:grid;grid-template-columns:1fr;gap:40px;align-items:center}
@media(min-width:960px){.hero-grid{grid-template-columns:1.15fr 1fr}}
.hero-calc-wrap{display:flex;flex-direction:column;gap:10px}
.hero-calc-caption{text-align:center;font-size:.85rem;color:var(--gray-500);margin:0}
.hero-calc-caption a{color:var(--primary-600);font-weight:700}

.scicalc{background:var(--gray-900);border-radius:var(--radius-lg);padding:16px;box-shadow:var(--shadow-lg);max-width:480px;margin:0 auto;width:100%}
.scicalc-display{background:#0d1117;color:#fff;font-family:ui-monospace,SFMono-Regular,Menlo,Consolas,monospace;font-size:1.5rem;text-align:right;padding:16px 14px;border-radius:var(--radius-sm);min-height:1.6em;overflow-x:auto;white-space:nowrap;margin-bottom:4px}
.scicalc-anglelabel{color:var(--gray-400);font-size:.68rem;font-weight:700;letter-spacing:.06em;text-align:right;padding:0 4px 8px;text-transform:uppercase}
.scicalc-grid{display:grid;grid-template-columns:repeat(10,1fr);gap:5px}
.scicalc-btn{background:#2a3140;color:#fff;border:none;border-radius:6px;padding:9px 2px;font-size:.74rem;font-weight:600;cursor:pointer;transition:background .1s;font-family:inherit;line-height:1.2}
.scicalc-btn:hover{background:#394253}
.scicalc-btn:active{transform:scale(.95)}
.scicalc-eq{background:var(--primary-500)}
.scicalc-eq:hover{background:var(--primary-600)}
.scicalc-ac{background:var(--danger-500)}
.scicalc-ac:hover{background:#c73c33}
.scicalc-degrad{display:flex;flex-direction:column;justify-content:center;gap:3px;font-size:.6rem;color:#cbd3e0;font-weight:600}
.scicalc-degrad label{display:flex;align-items:center;gap:3px;cursor:pointer;white-space:nowrap}
.scicalc-degrad input{width:auto;margin:0}

.scicalc-compact{max-width:440px}
.scicalc-compact .scicalc-display{font-size:1.2rem;padding:12px 12px}

@media(max-width:480px){
  .scicalc{padding:12px}
  .scicalc-grid{gap:3px}
  .scicalc-btn{font-size:.62rem;padding:7px 1px}
  .scicalc-display{font-size:1.1rem;padding:12px 10px}
  .scicalc-degrad{font-size:.55rem}
}

.calc-tool-standalone{padding:20px}
@media(min-width:640px){.calc-tool-standalone{padding:28px}}