/* perfday — dark-first, follows OS theme; [data-theme] overrides */
:root{
  --bg:#0D1117;--surface:#161B22;--panel:#0F141B;--track:#232A34;--line:#2A313C;
  --fg:#E6EDF3;--muted:#9AA4B2;--accent:#F5A524;--accent-ink:#0D1117;--chip:#221C10;
  --sans:Inter,system-ui,-apple-system,"Segoe UI",sans-serif;
  --mono:"JetBrains Mono",ui-monospace,SFMono-Regular,Menlo,monospace;
}
@media (prefers-color-scheme: light){
  :root:not([data-theme="dark"]){
    --bg:#FAFAF7;--surface:#FFFFFF;--panel:#F6F5F0;--track:#ECEBE4;--line:#E3E3DC;
    --fg:#16181D;--muted:#5B6270;--accent:#B45309;--accent-ink:#FFFFFF;--chip:#FBF1E3;
  }
}
:root[data-theme="light"]{
  --bg:#FAFAF7;--surface:#FFFFFF;--panel:#F6F5F0;--track:#ECEBE4;--line:#E3E3DC;
  --fg:#16181D;--muted:#5B6270;--accent:#B45309;--accent-ink:#FFFFFF;--chip:#FBF1E3;
}

*{box-sizing:border-box}
body{margin:0;background:var(--bg);color:var(--fg);font:16px/1.6 var(--sans)}
a{color:inherit}
a:hover{opacity:.85}
code,.mono,pre{font-family:var(--mono)}
.sans{font-family:var(--sans)}
.muted{color:var(--muted)}
.accent{color:var(--accent)}
.small{font-size:14px}
.wrap{max-width:1200px;margin:0 auto;padding-left:16px;padding-right:16px}
@media (min-width:640px){.wrap{padding-left:24px;padding-right:24px}}
h1,h2,h3{letter-spacing:-.01em;line-height:1.2}
:focus-visible{outline:2px solid var(--accent);outline-offset:2px}

/* header / footer */
.hdr{border-bottom:1px solid var(--line)}
.hdr-in{display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:12px;padding-top:12px;padding-bottom:12px}
.logo{font-family:var(--mono);font-weight:700;font-size:20px;text-decoration:none}
.logo span{color:var(--accent)}
.nav{display:flex;align-items:center;gap:20px;font-size:15px}
.nav a{text-decoration:none;color:var(--muted)}
.icon-btn{width:44px;height:44px;display:flex;align-items:center;justify-content:center;background:transparent;border:1px solid var(--line);border-radius:8px;color:var(--fg);cursor:pointer}
.ftr{border-top:1px solid var(--line);margin-top:48px}
.ftr-in{display:flex;flex-wrap:wrap;justify-content:space-between;gap:12px;padding-top:24px;padding-bottom:24px;font-size:14px;color:var(--muted)}

/* shared */
.card{background:var(--surface);border:1px solid var(--line);border-radius:12px}
.label{margin:0 0 8px;font-family:var(--mono);font-size:12px;letter-spacing:.06em;text-transform:uppercase;color:var(--muted)}
.label.accent{color:var(--accent)}
.chip{align-self:flex-start;font-family:var(--mono);font-size:13px;padding:4px 8px;border-radius:6px;background:var(--chip);color:var(--accent);overflow-wrap:anywhere}
.link{color:var(--accent);font-weight:600;text-decoration:none;font-size:14px}
.btn{display:inline-flex;align-items:center;min-height:44px;padding:0 16px;border-radius:8px;border:1px solid var(--line);background:transparent;color:var(--fg);font:500 14px var(--sans);cursor:pointer;text-decoration:none}
.btn-primary{background:var(--accent);border-color:var(--accent);color:var(--accent-ink);font-weight:600}
.pill{display:inline-flex;align-items:center;min-height:44px;padding:0 16px;border-radius:999px;border:1px solid var(--line);text-decoration:none;font-size:14px}
.chips{display:flex;flex-wrap:wrap;gap:10px}

/* home */
.hero{display:flex;flex-wrap:wrap;gap:40px;align-items:center;padding-top:56px;padding-bottom:40px}
.hero-main{flex:999 1 480px;min-width:0}
.kicker{margin:0 0 14px;font-size:13px;letter-spacing:.04em;color:var(--accent)}
.hero-h1{margin:0 0 14px;font-size:clamp(34px,6vw,52px);line-height:1.08;letter-spacing:-.02em}
.lede{margin:0 0 24px;font-size:18px;color:var(--muted);max-width:720px}
.search{position:relative;display:flex;flex-direction:column;gap:6px;max-width:520px}
.search input{height:48px;padding:0 14px;border-radius:8px;border:1px solid var(--line);background:var(--surface);color:var(--fg);font-size:15px}
.search-results{position:absolute;top:100%;left:0;right:0;margin:6px 0 0;padding:6px;list-style:none;background:var(--surface);border:1px solid var(--line);border-radius:10px;z-index:5}
.search-results a{display:block;padding:10px 12px;border-radius:6px;text-decoration:none}
.search-results a:hover,.search-results a:focus{background:var(--chip)}
.fotd{flex:1 1 320px;min-width:0;padding:24px}
.fotd-f{margin:0 0 6px;font-size:30px;font-weight:700}
.fotd-work{border-top:1px dashed var(--line);margin:14px 0;padding-top:14px;font-size:14px;line-height:1.9}
.section{padding-top:24px;padding-bottom:40px}
.section-h{display:flex;flex-wrap:wrap;align-items:baseline;justify-content:space-between;gap:8px;margin-bottom:18px}
.section-h h2,.split-main h2{margin:0;font-size:26px}
.tool-cards{display:grid;grid-template-columns:repeat(auto-fill,minmax(min(100%,300px),1fr));gap:16px}
.tool-card,.sheet-card{display:flex;flex-direction:column;gap:10px;padding:20px;text-decoration:none}
.tc-name{font-size:17px;font-weight:600}
.split{display:flex;flex-wrap:wrap;gap:32px}
.split-main{flex:999 1 520px;min-width:0}
.split-side{flex:1 1 300px;min-width:0;display:flex;flex-direction:column;gap:16px}
.ref-list{list-style:none;margin:16px 0 0;padding:0;border-top:1px solid var(--line)}
.ref-list li{border-bottom:1px solid var(--line)}
.ref-list a{display:flex;justify-content:space-between;align-items:center;gap:12px;min-height:52px;text-decoration:none;font-weight:500}

/* topic page */
.page{padding-top:28px}
.crumb{margin:0 0 10px;color:var(--muted)}
.crumb a{color:var(--muted)}
.page-h1{margin:0 0 10px;font-size:clamp(30px,5vw,40px);letter-spacing:-.02em}
.article{max-width:760px;margin-top:40px;display:flex;flex-direction:column;gap:40px;font-size:17px;line-height:1.65}
.article h2{margin:0 0 12px;font-size:23px}
.article p{margin:0 0 12px}
.h-sm{font-size:19px!important}
.facts{overflow-x:auto;border:1px solid var(--line);border-radius:10px}
.facts table{width:100%;border-collapse:collapse;font-size:15px}
.facts tr+tr{border-top:1px solid var(--line)}
.facts th{text-align:left;padding:12px 16px;width:36%;color:var(--muted);font-weight:500;vertical-align:top}
.facts td{padding:12px 16px}
pre.work{margin:0 0 12px;padding:16px 18px;border-radius:10px;background:var(--panel);border:1px solid var(--line);font-size:14px;line-height:1.8;overflow-x:auto}
.faqs{border-top:1px solid var(--line)}
.faqs details{border-bottom:1px solid var(--line);padding:14px 0}
.faqs summary{cursor:pointer;font-weight:600}
.faqs details p{margin:10px 0 0;color:var(--muted)}
.sources{margin:0;padding-left:20px;font-size:15px;display:flex;flex-direction:column;gap:8px}
.sources a{color:var(--accent)}

/* tool kit */
.tool{padding:20px;display:flex;flex-direction:column;gap:22px}
@media (min-width:640px){.tool{padding:24px}}
.tool-grid{display:flex;flex-wrap:wrap;gap:24px}
.tool-in{flex:1 1 320px;min-width:0;display:flex;flex-direction:column;gap:18px}
.field{display:flex;flex-direction:column;gap:6px}
.field-h{display:flex;justify-content:space-between;align-items:baseline;gap:12px}
.field label{font-weight:600}
.field label code{color:var(--muted);font-weight:400}
.field output{font-family:var(--mono);font-size:18px;font-weight:700}
.field input[type=range]{width:100%;height:44px;accent-color:var(--accent)}
.field input[type=number],.field select,.field textarea{width:100%;min-height:48px;padding:10px 12px;border-radius:8px;border:1px solid var(--line);background:var(--panel);color:var(--fg);font:16px var(--mono)}
.field textarea{min-height:160px;resize:vertical}
.seg{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:4px;padding:4px;border-radius:10px;background:var(--panel);border:1px solid var(--line)}
.seg button{min-height:44px;border:0;border-radius:8px;background:transparent;color:var(--fg);font:700 14px var(--mono);cursor:pointer}
.seg button[aria-pressed="true"]{background:var(--accent);color:var(--accent-ink)}
.actions{display:flex;flex-wrap:wrap;gap:8px}
.result{flex:1 1 280px;min-width:0;padding:20px;border-radius:12px;background:var(--panel);border:1px solid var(--line);display:flex;flex-direction:column;gap:14px;font-family:var(--mono)}
.r-big{font-size:clamp(36px,8vw,48px);font-weight:700;line-height:1.1;color:var(--accent);overflow-wrap:anywhere}
.r-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}
.r-grid .label{margin:0 0 2px;text-transform:none;letter-spacing:0}
.r-mid{font-size:20px;font-weight:700}
.result p{margin:0;font-family:var(--sans);font-size:14px;color:var(--muted)}
.result strong{color:var(--fg)}
.chart{margin:0}
.chart svg{width:100%;height:auto;display:block}
.chart text{font-family:var(--mono);font-size:11px;fill:var(--muted)}
.chart .axis{stroke:var(--line)}
.chart .ideal{fill:none;stroke:var(--muted);stroke-width:1.5;stroke-dasharray:4 4}
.chart .curve{fill:none;stroke:var(--accent);stroke-width:2.5}
.chart .hline{stroke:var(--accent);stroke-dasharray:2 4}
.chart .hl{fill:var(--accent)}
.chart .dot{fill:var(--accent);stroke:var(--surface);stroke-width:2}
.chart .bar{fill:var(--accent);opacity:.85}
.pct td,.pct th{padding:8px 12px;text-align:right}
.pct th:first-child,.pct td:first-child{text-align:left}
.pct table{width:100%;border-collapse:collapse;font-size:15px}
.pct tr+tr{border-top:1px solid var(--line)}

/* sticky result on phones */
@media (max-width:639px){
  .tool .result.sticky{position:sticky;bottom:0;z-index:4;box-shadow:0 -8px 24px rgba(0,0,0,.25)}
}