/* Layout: thermal duality. Hot (copper) and cool (coolant teal) carry the whole identity; one bold moment is the rack heat map in the hero, everything else stays quiet. */
:root{
  --bg:#EDF1F2; --surface:#F8FAFA; --ink:#0E1B26; --muted:#4A5C69; --line:#C6D1D7;
  --cool:#1B7F8C; --hot:#C8501B; --accent:#B34410; --on-accent:#FFFFFF;
  --display:"Bricolage Grotesque","Helvetica Neue",Arial,sans-serif;
  --body:"IBM Plex Sans","Helvetica Neue",Arial,sans-serif;
  --mono:"IBM Plex Mono",ui-monospace,Menlo,Consolas,monospace;
}
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){
    --bg:#0A141B; --surface:#111E27; --ink:#E8EEF1; --muted:#9DB0BB; --line:#23343F;
    --cool:#3DB5C4; --hot:#F07C4A; --accent:#F07C4A; --on-accent:#0A141B; color-scheme:dark;
  }
}
:root[data-theme="dark"]{
  --bg:#0A141B; --surface:#111E27; --ink:#E8EEF1; --muted:#9DB0BB; --line:#23343F;
  --cool:#3DB5C4; --hot:#F07C4A; --accent:#F07C4A; --on-accent:#0A141B; color-scheme:dark;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--ink);font-family:var(--body);font-size:17px;line-height:1.6;-webkit-font-smoothing:antialiased}
a{color:inherit}
:focus-visible{outline:2px solid var(--accent);outline-offset:3px;border-radius:2px}
.wrap{max-width:1120px;margin-inline:auto;padding-inline:20px}
h1,h2,h3{font-family:var(--display);font-weight:600;line-height:1.1;letter-spacing:-0.02em;text-wrap:balance;margin:0}
h1{font-size:clamp(2.3rem,5.6vw,4rem)}
h2{font-size:clamp(1.6rem,3.2vw,2.3rem)}
h3{font-size:1.2rem;letter-spacing:-0.01em}
p{margin:0;max-width:65ch}
.eyebrow{font-family:var(--mono);font-size:.74rem;letter-spacing:.12em;text-transform:uppercase;color:var(--muted)}

.site{font-family:var(--body)}
.site[lang="zh-CN"]{--display:"Noto Sans SC","PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;--body:"Noto Sans SC","PingFang SC","Hiragino Sans GB","Microsoft YaHei",sans-serif;--sl-pre:"第 ";--sl-post:" 步";line-height:1.75}
.site[lang="zh-CN"] h1,.site[lang="zh-CN"] h2,.site[lang="zh-CN"] h3{letter-spacing:0;line-height:1.25}
.site[lang="zh-CN"] .eyebrow,.site[lang="zh-CN"] .crumbs,.site[lang="zh-CN"] th,.site[lang="zh-CN"] .chip,.site[lang="zh-CN"] .steps li::before,.site[lang="zh-CN"] .split .k,.site[lang="zh-CN"] .foot-grid h4,.site[lang="zh-CN"] dt,.site[lang="zh-CN"] .group-label h3{letter-spacing:.04em}
.lang{display:inline-flex;border:1px solid var(--line);margin-left:6px;font-family:var(--mono);font-size:.78rem}
.nav .lang a{padding:7px 10px;color:var(--muted);text-decoration:none;box-shadow:none;margin:0}
.nav .lang a[aria-current="true"]{background:var(--ink);color:var(--bg)}
.nav .lang a:hover:not([aria-current="true"]){color:var(--ink)}
.nav{align-items:center}

/* header */
.site-head{border-bottom:1px solid var(--line);background:var(--bg);position:sticky;top:env(safe-area-inset-top,0px);z-index:5}
.site-head .wrap{display:flex;flex-wrap:wrap;align-items:center;justify-content:space-between;gap:8px 24px;padding-block:14px}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none;font-family:var(--display);font-weight:700;font-size:1.2rem;letter-spacing:-0.02em}
.brand svg{flex:none}
.nav{display:flex;gap:4px;font-size:.95rem;overflow-x:auto;max-width:100%}
.nav a{padding:8px 12px;text-decoration:none;color:var(--muted);border-radius:2px;white-space:nowrap}
.nav a:hover{color:var(--ink)}
.nav a[aria-current="page"]{color:var(--ink);box-shadow:inset 0 -2px 0 var(--accent)}
.nav a.cta{background:var(--accent);color:var(--on-accent);margin-left:6px}
.nav a.cta:hover{color:var(--on-accent);filter:brightness(1.08)}

/* hero */
.hero{padding-block:clamp(40px,7vw,88px) clamp(32px,5vw,56px)}
.hero .wrap{display:grid;grid-template-columns:minmax(0,1.05fr) minmax(0,1fr);gap:clamp(28px,5vw,64px);align-items:center}
.hero h1 span{color:var(--cool)}
.hero .lead{margin-top:20px;font-size:1.15rem;color:var(--muted)}
.actions{display:flex;flex-wrap:wrap;gap:12px;margin-top:28px}
.btn{display:inline-block;padding:13px 22px;background:var(--accent);color:var(--on-accent);text-decoration:none;font-weight:600;border:1px solid var(--accent);border-radius:2px;font-family:var(--body);font-size:1rem;cursor:pointer}
.btn:hover{filter:brightness(1.08)}
.btn.ghost{background:transparent;color:var(--ink);border-color:var(--ink)}
.btn.ghost:hover{background:var(--ink);color:var(--bg);filter:none}

.heat{background:var(--surface);border:1px solid var(--line);padding:16px;min-width:0}
.heat-grid{display:grid;grid-template-columns:repeat(16,1fr);gap:3px}
.heat-grid i{aspect-ratio:1;display:block;background:color-mix(in oklab,var(--hot) calc(var(--p) * 1%),var(--cool));border-radius:1px}
.heat-scale{display:flex;justify-content:space-between;gap:8px;margin-top:12px;font-family:var(--mono);font-size:.7rem;color:var(--muted);letter-spacing:.04em}
.heat-bar{height:6px;margin-top:8px;background:linear-gradient(90deg,var(--hot),var(--cool))}
.heat-cap{margin-top:12px;font-size:.82rem;color:var(--muted)}

/* sections */
section.block{padding-block:clamp(44px,6vw,80px);border-top:1px solid var(--line)}
.sec-head{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1.4fr);gap:12px 48px;margin-bottom:36px;align-items:end}
.sec-head p{color:var(--muted)}
.group-label{display:flex;align-items:baseline;gap:12px;margin:34px 0 0;padding-bottom:10px;border-bottom:2px solid var(--ink)}
.group-label h3{font-size:1rem;font-family:var(--mono);font-weight:500;letter-spacing:.1em;text-transform:uppercase}
.group-label .tag{width:10px;height:10px;display:inline-block;background:var(--cool)}
.group-label .tag.hot{background:var(--hot)}
.rows{list-style:none;margin:0;padding:0}
.rows li a{display:grid;grid-template-columns:minmax(0,1.1fr) minmax(0,1.6fr) minmax(0,.9fr);gap:8px 28px;padding:22px 4px;border-bottom:1px solid var(--line);text-decoration:none;align-items:baseline}
.rows li a:hover{background:var(--surface)}
.rows h3{font-size:1.45rem}
.rows p{color:var(--muted);font-size:.98rem}
.rows .metric{font-family:var(--mono);font-size:.78rem;color:var(--muted);letter-spacing:.03em}
.rows .arrow{color:var(--accent)}

.split{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:32px}
.split h3{margin-bottom:8px}
.split p{color:var(--muted);font-size:.98rem}
.split .k{font-family:var(--mono);font-size:.74rem;letter-spacing:.1em;text-transform:uppercase;color:var(--cool);display:block;margin-bottom:10px}

.cta-band{background:var(--ink);color:var(--bg);padding-block:clamp(40px,6vw,72px)}
.cta-band .wrap{display:flex;flex-wrap:wrap;gap:20px 40px;align-items:center;justify-content:space-between}
.cta-band h2{max-width:20ch}
.cta-band .btn{background:var(--bg);color:var(--ink);border-color:var(--bg)}

/* sub pages */
.page-head{padding-block:clamp(36px,6vw,72px) clamp(28px,4vw,44px)}
.crumbs{font-family:var(--mono);font-size:.76rem;letter-spacing:.06em;color:var(--muted);margin-bottom:22px}
.crumbs a{text-decoration:none}
.crumbs a:hover{text-decoration:underline}
.page-head .lead{margin-top:20px;font-size:1.18rem;color:var(--muted)}
.chip{display:inline-block;font-family:var(--mono);font-size:.72rem;letter-spacing:.1em;text-transform:uppercase;padding:4px 9px;border:1px solid var(--line);margin-bottom:18px}
.chip.hot{color:var(--hot);border-color:var(--hot)}
.chip.cool{color:var(--cool);border-color:var(--cool)}
.cols{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:36px}
.cols h3{margin-bottom:8px}
.cols p{color:var(--muted);font-size:.98rem}
.cols > div{border-top:2px solid var(--ink);padding-top:16px}
.proof{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:36px}
.proof > div{border-top:3px solid var(--accent);padding-top:18px}
.proof .stat{display:block;font-family:var(--display);font-weight:700;font-size:clamp(2rem,3.6vw,2.8rem);line-height:1.05;letter-spacing:-0.03em;margin-bottom:14px}
.proof h3{font-size:1.1rem;margin-bottom:8px}
.proof p{color:var(--muted);font-size:.98rem}
.proof-note{margin-top:22px;font-size:.85rem;color:var(--muted)}
table.cmp td.win{color:var(--ink);font-weight:600}
table.cmp th:last-child{color:var(--accent)}
.table-scroll{overflow-x:auto;border:1px solid var(--line);background:var(--surface)}
table{border-collapse:collapse;width:100%;min-width:560px;font-size:.95rem}
th,td{text-align:left;padding:13px 16px;border-bottom:1px solid var(--line);vertical-align:top}
th{font-family:var(--mono);font-size:.72rem;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);font-weight:500}
tr:last-child td{border-bottom:0}
td.u{font-family:var(--mono);font-size:.85rem;white-space:nowrap}
.steps{list-style:none;margin:0;padding:0;display:grid;grid-template-columns:repeat(4,minmax(0,1fr));gap:24px;counter-reset:s}
.steps li{counter-increment:s;border-top:2px solid var(--cool);padding-top:14px}
.steps li::before{content:var(--sl-pre,"Step ") counter(s) var(--sl-post,"");display:block;font-family:var(--mono);font-size:.72rem;letter-spacing:.1em;text-transform:uppercase;color:var(--cool);margin-bottom:8px}
.steps h3{font-size:1.1rem;margin-bottom:6px}
.steps p{font-size:.94rem;color:var(--muted)}
.related{display:flex;flex-wrap:wrap;gap:10px}
.related a{padding:10px 16px;border:1px solid var(--line);text-decoration:none;background:var(--surface)}
.related a:hover{border-color:var(--accent)}

/* contact */
.contact-grid{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1.2fr);gap:clamp(28px,5vw,64px)}
.contact-grid dl{margin:24px 0 0;display:grid;gap:18px}
.contact-grid dt{font-family:var(--mono);font-size:.72rem;letter-spacing:.1em;text-transform:uppercase;color:var(--muted)}
.contact-grid dd{margin:4px 0 0;font-size:1.1rem;user-select:all}
form{display:grid;gap:16px;background:var(--surface);border:1px solid var(--line);padding:clamp(18px,3vw,28px)}
label{display:grid;gap:6px;font-size:.88rem;font-weight:500}
input,select,textarea{font:inherit;color:var(--ink);background:var(--bg);border:1px solid var(--line);padding:11px 12px;border-radius:2px;width:100%;min-width:0}
textarea{min-height:130px;resize:vertical}
.fields{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:16px}
.note{font-size:.85rem;color:var(--muted)}
#out{font-family:var(--mono);font-size:.85rem;min-height:0}

footer.site-foot{border-top:1px solid var(--line);padding-block:44px 32px;background:var(--bg)}
.foot-grid{display:grid;grid-template-columns:minmax(0,1.2fr) repeat(3,minmax(0,1fr));gap:32px}
.foot-grid h4{font-family:var(--mono);font-size:.72rem;letter-spacing:.1em;text-transform:uppercase;color:var(--muted);margin:0 0 12px;font-weight:500}
.foot-grid ul{list-style:none;margin:0;padding:0;display:grid;gap:6px;font-size:.95rem}
.foot-grid a{text-decoration:none}
.foot-grid a:hover{text-decoration:underline}
.legal{margin-top:36px;padding-top:18px;border-top:1px solid var(--line);font-size:.82rem;color:var(--muted);display:flex;flex-wrap:wrap;gap:8px 24px;justify-content:space-between}

@media (max-width:860px){
  .hero .wrap,.sec-head,.contact-grid{grid-template-columns:minmax(0,1fr)}
  .split,.cols,.proof{grid-template-columns:minmax(0,1fr)}
  .steps{grid-template-columns:repeat(2,minmax(0,1fr))}
  .rows li a{grid-template-columns:minmax(0,1fr)}
  .foot-grid{grid-template-columns:minmax(0,1fr) minmax(0,1fr)}
  .foot-grid > :first-child{grid-column:1/-1}
}
@media (max-width:520px){
  body{font-size:16px}
  .steps,.fields{grid-template-columns:minmax(0,1fr)}
  .heat-grid{gap:2px}
}
@media (prefers-reduced-motion:no-preference){
  .heat-grid i{transition:filter .2s}
  .heat-grid i:hover{filter:brightness(1.25)}
}

/* liquid loop illustration */
.heat-scale span{display:inline-flex;align-items:center;gap:8px}
.heat-scale .sw{width:10px;height:10px;display:inline-block}
.flow{stroke-dasharray:2 10;stroke-linecap:round}
.heat{padding:20px}
@media (prefers-reduced-motion:no-preference){
  .flow-out{animation:fout 1.4s linear infinite}
  .flow-in{animation:fout 1.4s linear infinite}
}
@keyframes fout{to{stroke-dashoffset:-24}}