/* ============================================================
   funnel.css — shared styling for pricing.html & signup.html
   Mathematics for Machine Learning · freemium funnel
   Design tokens live in css/tokens.css (linked before this file).
   ============================================================ */
*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  background:var(--paper);
  color:var(--ink);
  font-family:var(--sans);
  min-height:100vh;
  -webkit-font-smoothing:antialiased;
  text-rendering:optimizeLegibility;
}
a{color:inherit;text-decoration:none}
button{font-family:inherit}
::selection{background:var(--accent-soft);color:var(--accent-ink)}

/* ---------- TOP NAV ---------- */
.fnav{
  display:flex;align-items:center;gap:12px;
  padding:16px 28px;
  border-bottom:1px solid var(--line);
  background:rgba(238,240,244,.86);
  backdrop-filter:saturate(1.2) blur(10px);
  position:sticky;top:0;z-index:40;
}
.fnav .brand{display:flex;align-items:center;gap:11px;cursor:pointer;user-select:none}
.fglyph{
  width:34px;height:34px;border-radius:9px;flex:none;
  display:grid;place-items:center;
  background:var(--glyph-bg);color:var(--glyph-ink);
  font-family:var(--serif);font-style:italic;font-size:21px;font-weight:500;
  letter-spacing:-.02em;
}
.fnav b{font-weight:600;font-size:15px;letter-spacing:-.01em}
.fnav .spacer{flex:1}
.fnav-link{
  border:none;background:none;cursor:pointer;
  font-family:inherit;font-size:13.5px;font-weight:500;color:var(--muted);
  transition:color .15s;
}
.fnav-link:hover{color:var(--ink)}

/* ---------- shared buttons ---------- */
.btn{
  font-family:inherit;cursor:pointer;border-radius:11px;
  font-size:14.5px;font-weight:600;
  transition:background .15s,border-color .15s,color .15s,transform .12s;
  display:inline-flex;align-items:center;justify-content:center;gap:9px;
}
.btn-cta{background:var(--accent);color:#fff;border:none;padding:14px;}
.btn-cta:hover{background:var(--accent-ink)}
.btn-ghost{background:var(--panel);color:var(--ink);border:1px solid var(--line);padding:14px;}
.btn-ghost:hover{border-color:var(--accent);color:var(--accent-ink)}

/* ============================================================
   PRICING
   ============================================================ */
.pricing-wrap{max-width:920px;margin:0 auto;padding:56px 28px 70px;text-align:center}
.kicker{
  font-family:var(--mono);font-size:12px;letter-spacing:.18em;
  text-transform:uppercase;color:var(--accent-ink);
}
.pricing-h1{
  font-family:var(--serif);font-weight:500;font-size:50px;line-height:1.05;
  letter-spacing:-.025em;margin:16px 0 0;
}
.pricing-h1 em{font-style:italic;color:var(--accent)}
.pricing-lede{
  font-family:var(--serif);font-size:18px;color:var(--muted);
  margin:18px auto 0;max-width:500px;line-height:1.5;
}

/* billing toggle (segmented) */
.bill-toggle{
  display:inline-flex;align-items:center;gap:4px;
  background:var(--panel-2);border-radius:11px;padding:4px;margin:30px 0 36px;
}
.seg{
  border:none;cursor:pointer;font-family:inherit;font-size:13.5px;font-weight:600;
  padding:9px 18px;border-radius:8px;color:var(--muted);background:transparent;
  display:flex;align-items:center;gap:8px;
  transition:background .15s,color .15s,box-shadow .15s;
}
.seg.active{background:var(--panel);color:var(--ink);box-shadow:0 1px 3px rgba(20,22,30,.14)}
.save-tag{
  font-family:var(--mono);font-size:10.5px;font-weight:600;
  background:var(--ml-bg);color:var(--ml);border-radius:5px;padding:2px 6px;
}

/* cards */
.price-grid{display:grid;grid-template-columns:1fr 1fr;gap:18px;text-align:left}
.pcard{
  background:var(--panel);border:1px solid var(--line);border-radius:16px;
  padding:28px;display:flex;flex-direction:column;position:relative;
}
.pcard.pro{
  border:1.5px solid var(--accent);
  box-shadow:0 24px 50px -30px rgba(40,40,180,.6);
}
.ribbon{
  position:absolute;top:-12px;left:28px;
  font-family:var(--mono);font-size:10.5px;letter-spacing:.1em;
  text-transform:uppercase;font-weight:600;
  background:var(--accent);color:#fff;border-radius:7px;padding:5px 11px;
}
.plan-name{
  font-family:var(--mono);font-size:11.5px;letter-spacing:.1em;
  text-transform:uppercase;color:var(--faint);
}
.pcard.pro .plan-name{color:var(--accent-ink)}
.price-row{display:flex;align-items:baseline;gap:4px;margin:14px 0 4px}
.price-row .amount{
  font-family:var(--sans);font-weight:700;font-size:50px;letter-spacing:-.03em;
}
.price-row .period{font-size:15px;color:var(--faint)}
.price-sub{font-size:13px;color:var(--faint)}
.price-sub.save{color:var(--ml);font-weight:500}
.pcard hr{border:none;height:1px;background:var(--line-2);margin:22px 0}
.feats{display:flex;flex-direction:column;gap:13px;font-size:14.5px;color:#3a3f4a;flex:1}
.feat{display:flex;gap:11px}
.feat .tick{flex:none}
.feat.free .tick{color:var(--good)}
.feat.pro .tick{color:var(--accent)}
.feat b{font-weight:600}
.pcard .btn{margin-top:26px}
.pcard.free .btn{margin-top:auto}
.card-fine{text-align:center;font-size:12px;color:var(--faint);margin-top:11px}
.pricing-fine{margin-top:30px;font-size:13px;color:var(--faint)}

/* pay-once strip — one payment, one year of Pro (Alipay/WeChat-friendly) */
.once-strip{
  margin-top:18px;display:flex;align-items:center;gap:18px;text-align:start;
  background:var(--panel);border:1px solid var(--line);border-radius:16px;
  padding:18px 22px;
}
.once-txt{flex:1;display:flex;flex-direction:column;gap:3px}
.once-strip b{font-size:15px}
.once-sub{font-size:13.5px;color:var(--faint)}
.once-note{font-family:var(--mono);font-size:11px;letter-spacing:.04em;color:var(--faint)}
.once-strip .btn{margin:0;flex:none}
@media(max-width:760px){
  .once-strip{flex-direction:column;align-items:stretch;text-align:center}
  .once-txt{align-items:center}
}

/* ============================================================
   SIGN UP / LOG IN
   ============================================================ */
.auth-wrap{padding:54px 28px}
.auth-card{
  max-width:900px;margin:0 auto;background:var(--panel);
  border:1px solid var(--line);border-radius:18px;overflow:hidden;
  display:grid;grid-template-columns:1fr 1fr;
  box-shadow:0 24px 60px -34px rgba(20,30,80,.4);
}
/* left value panel */
.auth-aside{
  background:var(--accent-soft);padding:40px 36px;
  display:flex;flex-direction:column;border-right:1px solid var(--line-2);
}
.auth-aside .fglyph{width:40px;height:40px;border-radius:10px;font-size:24px}
.auth-aside h2{
  font-family:var(--serif);font-weight:500;font-size:30px;line-height:1.12;
  letter-spacing:-.02em;margin:24px 0 0;
}
.auth-aside p{
  font-family:var(--serif);font-size:16px;color:var(--muted);
  line-height:1.5;margin:14px 0 0;
}
.auth-aside .grow{flex:1}
.aside-feats{display:flex;flex-direction:column;gap:11px;margin-top:30px;font-size:14px;color:var(--muted)}
.aside-feats div{display:flex;gap:10px}
.aside-feats .tick{color:var(--good)}

/* right form */
.auth-form{padding:40px 36px}
.auth-tabs{
  display:flex;gap:4px;background:var(--panel-2);border-radius:10px;padding:4px;margin-bottom:26px;
}
.auth-tab{
  flex:1;border:none;cursor:pointer;font-family:inherit;font-size:13.5px;font-weight:600;
  padding:9px;border-radius:7px;color:var(--muted);background:transparent;
  transition:background .15s,color .15s,box-shadow .15s;
}
.auth-tab.active{background:var(--panel);color:var(--ink);box-shadow:0 1px 3px rgba(20,22,30,.14)}
.auth-title{
  font-family:var(--sans);font-weight:600;font-size:22px;letter-spacing:-.01em;margin:0;
}
.auth-subtitle{font-size:13.5px;color:var(--faint);margin:6px 0 22px}
.auth-form label{
  display:block;font-size:12.5px;font-weight:600;color:var(--muted);margin-bottom:7px;
}
.auth-in{
  width:100%;border:1px solid var(--line);border-radius:10px;padding:13px 14px;
  font-family:inherit;font-size:14.5px;background:var(--panel-2);color:var(--ink);
  transition:border-color .15s,box-shadow .15s;
}
.auth-in:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px var(--accent-soft)}
.auth-form .btn{width:100%;margin-top:14px;border-radius:10px}
.auth-form .btn-cta{padding:14px}
.auth-form .btn-ghost{padding:13px;font-size:14px}
.divider{
  display:flex;align-items:center;gap:12px;margin:22px 0;color:#b3b8c2;font-size:12px;
}
.divider::before,.divider::after{content:"";flex:1;height:1px;background:var(--line-2)}
.oauth-row{display:flex;gap:10px;margin-top:14px}
.oauth{
  flex:1;background:var(--panel-2);border:1px solid var(--line-2);border-radius:10px;
  padding:11px;font-family:inherit;font-size:13px;font-weight:600;color:var(--ink);
  cursor:pointer;display:inline-flex;align-items:center;justify-content:center;gap:8px;
  transition:border-color .15s,background .15s;
}
.oauth:hover{border-color:var(--line);background:var(--panel-2)}
.oauth svg{width:16px;height:16px;flex:none}
.auth-terms{font-size:11.5px;color:#a3a8b2;line-height:1.5;margin:22px 0 0;text-align:center}
.auth-terms a{color:var(--accent);font-weight:500}

/* ---------- RESPONSIVE ---------- */
@media(max-width:880px){
  .price-grid{grid-template-columns:1fr}
  .auth-card{grid-template-columns:1fr}
  .auth-aside{border-right:none;border-bottom:1px solid var(--line-2)}
  .pricing-h1{font-size:40px}
}
@media(max-width:560px){
  .fnav{padding:14px 18px}
  .pricing-wrap{padding:40px 18px 56px}
  .auth-wrap{padding:32px 18px}
  .auth-form,.auth-aside{padding:30px 24px}
  .pricing-h1{font-size:34px}
}