/* ==========================================================================
   Net Margin Lab — design system
   Light, calm, Stripe-ish. No frameworks, no external requests.
   ========================================================================== */

:root{
  --bg:#f6f9fc;
  --surface:#ffffff;
  --surface-2:#fbfcfe;
  --text:#0a2540;
  --text-2:#425466;
  --muted:#8898aa;
  --border:#e3e8ee;
  --border-strong:#cfd7df;

  --brand:#635bff;
  --brand-dark:#4f46e5;
  --brand-soft:#f0efff;

  --ok:#0e9f6e;
  --ok-soft:#e8f8f1;
  --bad:#e0483d;
  --bad-soft:#fdecea;
  --warn:#b7791f;
  --warn-soft:#fff8e6;

  --radius:14px;
  --radius-sm:9px;
  --shadow-sm:0 1px 2px rgba(10,37,64,.06), 0 1px 3px rgba(10,37,64,.04);
  --shadow:0 2px 6px rgba(10,37,64,.05), 0 14px 38px rgba(10,37,64,.07);
  --maxw:1080px;
  --mono:ui-monospace,SFMono-Regular,"SF Mono",Menlo,Consolas,monospace;
}

*,*::before,*::after{box-sizing:border-box}

html{-webkit-text-size-adjust:100%}

body{
  margin:0;
  background:var(--bg);
  color:var(--text);
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Inter,Roboto,"Helvetica Neue",Arial,"PingFang SC","Microsoft YaHei",sans-serif;
  font-size:16px;
  line-height:1.65;
  -webkit-font-smoothing:antialiased;
}

a{color:var(--brand-dark);text-decoration:none}
a:hover{text-decoration:underline}

h1,h2,h3,h4{line-height:1.25;margin:0 0 .5em;letter-spacing:-.018em;font-weight:700}
h1{font-size:clamp(1.7rem,4.4vw,2.5rem);letter-spacing:-.028em}
h2{font-size:1.35rem;margin-top:2em}
h3{font-size:1.06rem;margin-top:1.6em}
p{margin:0 0 1em}
ul,ol{padding-left:1.25em}
li{margin:.35em 0}
small{font-size:.82rem}

.wrap{max-width:var(--maxw);margin:0 auto;padding:0 20px}
.narrow{max-width:760px;margin:0 auto;padding:0 20px}

/* ---------- header ---------- */
header.site{
  background:rgba(255,255,255,.88);
  backdrop-filter:saturate(180%) blur(12px);
  border-bottom:1px solid var(--border);
  position:sticky;top:0;z-index:40;
}
header.site .wrap{display:flex;align-items:center;gap:14px;height:62px}
.logo{display:flex;align-items:center;gap:9px;font-weight:800;font-size:1.03rem;color:var(--text);letter-spacing:-.02em}
.logo:hover{text-decoration:none}
.logo .mark{
  width:26px;height:26px;border-radius:8px;flex:0 0 auto;
  background:linear-gradient(135deg,#635bff,#8b5cf6 55%,#00d4ff);
  box-shadow:0 2px 6px rgba(99,91,255,.35);
  display:grid;place-items:center;color:#fff;font-size:.72rem;font-weight:800;
}
nav.top{margin-left:auto;display:flex;gap:6px;flex-wrap:wrap}
nav.top a{
  color:var(--text-2);font-size:.9rem;font-weight:500;
  padding:7px 11px;border-radius:8px;white-space:nowrap;
}
nav.top a:hover{background:var(--brand-soft);color:var(--brand-dark);text-decoration:none}
nav.top a.cta{background:var(--brand);color:#fff}
nav.top a.cta:hover{background:var(--brand-dark);color:#fff}

/* ---------- hero ---------- */
.hero{padding:56px 0 34px;text-align:center}
.hero p.lede{font-size:clamp(1rem,2.4vw,1.16rem);color:var(--text-2);max-width:660px;margin:0 auto 1.4em}
.hero .pill{
  display:inline-block;font-size:.76rem;font-weight:600;letter-spacing:.04em;
  text-transform:uppercase;color:var(--brand-dark);background:var(--brand-soft);
  border:1px solid #e0dcff;padding:5px 12px;border-radius:999px;margin-bottom:18px;
}
.hero-actions{display:flex;gap:10px;justify-content:center;flex-wrap:wrap}

/* ---------- buttons ---------- */
.btn{
  display:inline-block;font-size:.94rem;font-weight:600;padding:11px 20px;
  border-radius:10px;border:1px solid transparent;cursor:pointer;
  transition:background .15s ease,box-shadow .15s ease,transform .05s ease;
}
.btn:hover{text-decoration:none}
.btn-primary{background:var(--brand);color:#fff;box-shadow:0 2px 8px rgba(99,91,255,.28)}
.btn-primary:hover{background:var(--brand-dark);color:#fff}
.btn-ghost{background:var(--surface);color:var(--text);border-color:var(--border-strong);box-shadow:var(--shadow-sm)}
.btn-ghost:hover{background:var(--surface-2);color:var(--text)}
.btn:active{transform:translateY(1px)}

/* ---------- cards ---------- */
.grid{display:grid;gap:16px}
.grid.cols-2{grid-template-columns:repeat(auto-fit,minmax(300px,1fr))}
.grid.cols-3{grid-template-columns:repeat(auto-fit,minmax(260px,1fr))}

.card{
  background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);
  padding:22px;box-shadow:var(--shadow-sm);transition:box-shadow .18s ease,transform .18s ease,border-color .18s ease;
}
a.card{display:block;color:inherit}
a.card:hover{
  text-decoration:none;box-shadow:var(--shadow);transform:translateY(-2px);
  border-color:#d9d3ff;
}
.card h3{margin:0 0 .35em;font-size:1.06rem}
.card p{margin:0;color:var(--text-2);font-size:.92rem}
.card .tag{
  display:inline-block;font-size:.72rem;font-weight:700;letter-spacing:.03em;text-transform:uppercase;
  color:var(--brand-dark);background:var(--brand-soft);padding:3px 9px;border-radius:6px;margin-bottom:12px;
}
.card .tag.hot{color:#a13d00;background:#fff1e5}

/* ---------- calculator layout ---------- */
.calc{padding:30px 0 10px}
.calc-shell{
  display:grid;gap:20px;
  grid-template-columns:minmax(0,1fr) minmax(0,.85fr);
  align-items:start;
}
@media (max-width:860px){ .calc-shell{grid-template-columns:1fr} }

.panel{
  background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);
  padding:22px;box-shadow:var(--shadow-sm);
}
.panel > h2, .panel > h3{margin-top:0}
.panel.sticky{position:sticky;top:78px}

.field{margin-bottom:14px}
.field label{display:block;font-size:.86rem;font-weight:600;color:var(--text-2);margin-bottom:5px}
.field .hint{font-weight:400;color:var(--muted);font-size:.8rem;display:block;margin-top:2px}
.field input,.field select{
  width:100%;padding:10px 12px;font-size:.96rem;font-family:inherit;color:var(--text);
  background:var(--surface);border:1px solid var(--border-strong);border-radius:var(--radius-sm);
  transition:border-color .15s ease,box-shadow .15s ease;
}
.field input:focus,.field select:focus{
  outline:none;border-color:var(--brand);box-shadow:0 0 0 3px rgba(99,91,255,.16);
}
.field-row{display:grid;grid-template-columns:1fr 1fr;gap:12px}
@media (max-width:520px){ .field-row{grid-template-columns:1fr} }

.input-group{display:flex}
.input-group .pre{
  display:grid;place-items:center;padding:0 11px;font-size:.9rem;color:var(--muted);
  background:var(--surface-2);border:1px solid var(--border-strong);border-right:0;
  border-radius:var(--radius-sm) 0 0 var(--radius-sm);
}
.input-group input{border-radius:0 var(--radius-sm) var(--radius-sm) 0}

details.adv{margin:6px 0 14px;border-top:1px dashed var(--border);padding-top:12px}
details.adv > summary{
  cursor:pointer;font-size:.88rem;font-weight:600;color:var(--brand-dark);
  list-style:none;user-select:none;
}
details.adv > summary::-webkit-details-marker{display:none}
details.adv > summary::before{content:"+ ";font-weight:700}
details.adv[open] > summary::before{content:"– "}

/* ---------- results ---------- */
.result-hero{
  border-radius:var(--radius);padding:20px;margin-bottom:16px;
  background:linear-gradient(135deg,#f7f5ff,#eef4ff 55%,#f0fbff);
  border:1px solid #e2ddff;
}
.result-hero .label{font-size:.8rem;font-weight:700;letter-spacing:.05em;text-transform:uppercase;color:var(--brand-dark)}
.result-hero .value{font-size:clamp(1.8rem,6vw,2.5rem);font-weight:800;letter-spacing:-.03em;line-height:1.1;margin:4px 0 2px}
.result-hero .sub{font-size:.9rem;color:var(--text-2)}

table.break{width:100%;border-collapse:collapse;font-size:.91rem}
table.break th,table.break td{padding:7px 0;text-align:left;border-bottom:1px solid var(--border)}
table.break th{font-weight:500;color:var(--text-2);font-size:.86rem}
table.break td.amt{text-align:right;font-variant-numeric:tabular-nums;font-family:var(--mono);font-size:.87rem;white-space:nowrap}
table.break tr.total th,table.break tr.total td{
  border-bottom:0;border-top:2px solid var(--border-strong);font-weight:700;color:var(--text);padding-top:10px;
}
table.break tr.net td{color:var(--ok);font-weight:700}
table.break tr.neg td{color:var(--bad)}

.metrics{display:grid;grid-template-columns:repeat(auto-fit,minmax(110px,1fr));gap:10px;margin-top:16px}
.metric{background:var(--surface-2);border:1px solid var(--border);border-radius:var(--radius-sm);padding:11px 13px}
.metric .k{font-size:.76rem;color:var(--muted);font-weight:600;text-transform:uppercase;letter-spacing:.03em}
.metric .v{font-size:1.16rem;font-weight:700;font-variant-numeric:tabular-nums;margin-top:2px}

.note{font-size:.84rem;color:var(--muted);margin-top:14px;padding-top:12px;border-top:1px solid var(--border)}
.warnbox{
  background:var(--warn-soft);border:1px solid #ffe2a8;border-radius:var(--radius-sm);
  padding:12px 14px;font-size:.87rem;color:#6b4d0b;margin:14px 0;
}
.okbox{background:var(--ok-soft);border:1px solid #c6ecdb;border-radius:var(--radius-sm);padding:12px 14px;font-size:.87rem;color:#08634a;margin:14px 0}

/* ---------- prose / article ---------- */
.prose{max-width:760px}
.prose h2{margin-top:2.1em;padding-top:.2em}
.prose h2:first-child{margin-top:1em}
.prose table{width:100%;border-collapse:collapse;font-size:.89rem;margin:1em 0}
.prose th,.prose td{border:1px solid var(--border);padding:8px 10px;text-align:left}
.prose th{background:var(--surface-2);font-weight:600;color:var(--text-2)}
.prose td.num{font-variant-numeric:tabular-nums;font-family:var(--mono);font-size:.85rem}
.prose code{font-family:var(--mono);font-size:.86em;background:var(--brand-soft);padding:2px 5px;border-radius:4px;color:var(--brand-dark)}
.prose blockquote{
  margin:1.2em 0;padding:2px 0 2px 16px;border-left:3px solid var(--brand);
  color:var(--text-2);font-style:italic;
}

/* ---------- faq ---------- */
.faq details{
  background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-sm);
  margin-bottom:9px;box-shadow:var(--shadow-sm);
}
.faq summary{
  cursor:pointer;padding:14px 16px;font-weight:600;font-size:.95rem;list-style:none;
  display:flex;justify-content:space-between;gap:12px;align-items:baseline;
}
.faq summary::-webkit-details-marker{display:none}
.faq summary::after{content:"+";color:var(--brand);font-weight:700;flex:0 0 auto}
.faq details[open] summary::after{content:"–"}
.faq .ans{padding:0 16px 15px;color:var(--text-2);font-size:.92rem}
.faq .ans p:last-child{margin-bottom:0}

/* ---------- ad slots (placeholders until network is wired) ---------- */
.ad-slot{
  min-height:0;margin:26px 0;display:flex;align-items:center;justify-content:center;
  color:var(--muted);font-size:.75rem;letter-spacing:.06em;text-transform:uppercase;
}
.ad-slot[data-filled="false"]{display:none}
.ad-slot ins{display:block;width:100%}

/* ---------- footer ---------- */
footer.site{
  margin-top:64px;border-top:1px solid var(--border);background:var(--surface);
  padding:34px 0 44px;font-size:.88rem;color:var(--text-2);
}
footer.site .cols{display:grid;gap:22px;grid-template-columns:1.4fr 1fr 1fr 1fr}
@media (max-width:720px){ footer.site .cols{grid-template-columns:1fr 1fr} }
footer.site h4{font-size:.8rem;text-transform:uppercase;letter-spacing:.05em;color:var(--muted);margin-bottom:.7em}
footer.site ul{list-style:none;padding:0;margin:0}
footer.site li{margin:.4em 0}
footer.site a{color:var(--text-2)}
footer.site a:hover{color:var(--brand-dark)}
footer.site .legal{margin-top:26px;padding-top:18px;border-top:1px solid var(--border);color:var(--muted);font-size:.8rem}

/* ---------- misc ---------- */
.crumbs{font-size:.84rem;color:var(--muted);padding:18px 0 0}
.crumbs a{color:var(--muted)}
.crumbs span{margin:0 6px}
.updated{font-size:.8rem;color:var(--muted);border-left:3px solid var(--border-strong);padding-left:10px;margin:14px 0}
.skip{position:absolute;left:-9999px}
.srcs{font-size:.84rem;color:var(--text-2)}
.srcs li{margin:.3em 0}

/* ---------- comparison page ---------- */
.cmp{padding:13px 0;border-bottom:1px solid var(--border)}
.cmp:last-child{border-bottom:0;padding-bottom:2px}
.cmp-head{display:flex;align-items:baseline;justify-content:space-between;gap:10px}
.cmp-name{font-weight:600;font-size:.95rem;color:var(--text)}
.cmp-net{font-variant-numeric:tabular-nums;font-family:var(--mono);font-size:.98rem;font-weight:700;color:var(--text)}
.cmp-track{height:7px;background:var(--border);border-radius:99px;overflow:hidden;margin:7px 0 5px}
.cmp-fill{height:100%;background:var(--border-strong);border-radius:99px;transition:width .22s ease}
.cmp.best .cmp-fill{background:var(--ok)}
.cmp.best .cmp-net{color:var(--ok)}
.cmp.best .cmp-name::after{
  content:"best";margin-left:8px;font-size:.66rem;font-weight:700;letter-spacing:.06em;
  text-transform:uppercase;color:var(--ok);background:var(--ok-soft);
  border-radius:4px;padding:2px 5px;vertical-align:middle;
}
.cmp.neg .cmp-fill{background:var(--bad)}
.cmp.neg .cmp-net{color:var(--bad)}
.cmp-meta{font-size:.78rem;color:var(--muted);font-variant-numeric:tabular-nums}
.cmp-d{margin-top:6px}
.cmp-d summary{
  font-size:.78rem;color:var(--text-2);cursor:pointer;list-style:none;
  display:inline-block;padding:2px 0;border-bottom:1px dashed var(--border-strong);
}
.cmp-d summary::-webkit-details-marker{display:none}
.cmp-d summary:hover{color:var(--brand-dark);border-bottom-color:var(--brand)}
.cmp-d table.break{margin-top:8px}
.cmp-note{font-size:.78rem;color:var(--muted);margin:8px 0 2px;line-height:1.5}
@media (max-width:860px){ .panel.sticky{position:static} }