/* Pool Chemistry Calculator — site styles. Modern, not minimalistic. */
*,*::before,*::after{box-sizing:border-box}
html{scroll-behavior:smooth;-webkit-text-size-adjust:100%}
body{
  margin:0;font-family:'Inter',-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,sans-serif;
  color:#0e2336;background:#f6fafd;line-height:1.6;font-size:16px;
}
a{color:#0a6cad;text-decoration:none}
a:hover{text-decoration:underline}
img{max-width:100%;height:auto;display:block}

/* ---------- top bar ---------- */
.topbar{
  background:linear-gradient(135deg,#0a3b5c 0%,#0e7ab5 100%);
  color:#fff;border-bottom:3px solid #f0a500;
}
.topbar-inner{
  max-width:1200px;margin:0 auto;padding:14px 20px;
  display:flex;align-items:center;justify-content:space-between;gap:18px;
}
.brand{font-weight:800;letter-spacing:-0.01em;font-size:18px;color:#fff;display:flex;align-items:center;gap:10px}
.brand .logo-mark{
  background:#f0a500;color:#0a3b5c;font-weight:900;
  width:30px;height:30px;border-radius:6px;display:inline-flex;align-items:center;justify-content:center;font-size:15px;
}
.brand:hover{text-decoration:none}
.nav{display:flex;gap:6px;flex-wrap:wrap}
.nav a{
  color:#dbe9f5;padding:7px 12px;border-radius:6px;font-size:14px;font-weight:500;
}
.nav a:hover{background:rgba(255,255,255,0.12);color:#fff;text-decoration:none}
.nav a.cta{background:#f0a500;color:#0a3b5c;font-weight:700}
.nav a.cta:hover{background:#ffc14d}

/* ---------- breadcrumbs ---------- */
.breadcrumbs{
  max-width:1200px;margin:0 auto;padding:10px 20px;font-size:13px;color:#5a7794;
}
.breadcrumbs a{color:#0a6cad}
.breadcrumbs .sep{margin:0 6px;color:#a8bccd}

/* ---------- layout ---------- */
.wrap{max-width:1200px;margin:0 auto;padding:0 20px 60px}
.row{display:grid;grid-template-columns:1fr 320px;gap:36px}
@media(max-width:960px){.row{grid-template-columns:1fr}}

main{min-width:0}
.hero{
  background:linear-gradient(180deg,#fff 0%,#eaf3fa 100%);
  border:1px solid #d1e1ee;border-radius:14px;padding:28px 30px;margin:18px 0 24px;
  box-shadow:0 4px 14px rgba(14,122,181,0.06);
}
.hero h1{
  margin:0 0 10px;font-size:30px;line-height:1.25;color:#0a3b5c;letter-spacing:-0.02em;
}
.hero .h1-tagline{color:#1d6597;font-weight:600;font-size:16px;margin-bottom:14px}
.hero p.lead{margin:0;font-size:17px;color:#243f5a}

.badge-row{margin-top:14px;display:flex;flex-wrap:wrap;gap:8px}
.badge{
  display:inline-flex;align-items:center;gap:6px;font-size:12px;font-weight:600;
  background:#fff;color:#0a3b5c;border:1px solid #cfdfeb;
  padding:5px 10px;border-radius:99px;
}
.badge.green{background:#e9f9ee;color:#0a6a35;border-color:#bce5c8}
.badge.amber{background:#fff5dd;color:#7a5500;border-color:#f0d589}

/* ---------- calculator card ---------- */
.calc{
  background:#fff;border:1px solid #cddeec;border-radius:14px;padding:22px 24px;
  margin:18px 0;box-shadow:0 6px 18px rgba(10,59,92,0.07);
}
.calc h2{margin:0 0 16px;font-size:22px;color:#0a3b5c}
.calc .field{margin-bottom:14px}
.calc label{display:block;font-weight:600;font-size:14px;margin-bottom:6px;color:#1d3a55}
.calc .hint{font-size:12px;color:#5a7794;margin-top:4px}
.calc input,.calc select{
  width:100%;padding:10px 12px;font-size:15px;
  border:1px solid #c0d1e0;border-radius:8px;background:#fbfdff;color:#0e2336;
}
.calc input:focus,.calc select:focus{outline:2px solid #0e7ab5;border-color:#0e7ab5}
.calc .field-row{display:grid;grid-template-columns:1fr 1fr;gap:14px}
.calc .actions{display:flex;gap:10px;margin-top:6px}
.btn{
  display:inline-flex;align-items:center;gap:8px;
  padding:11px 20px;border-radius:8px;font-weight:700;font-size:15px;border:0;cursor:pointer;
}
.btn-primary{background:#0e7ab5;color:#fff}
.btn-primary:hover{background:#0a6cad}
.btn-secondary{background:#eaf3fa;color:#0a3b5c}

.result{
  margin-top:18px;background:linear-gradient(135deg,#e9f9ee 0%,#fff5dd 100%);
  border:1px solid #bce5c8;border-radius:10px;padding:16px 18px;
}
.result .label{font-size:13px;color:#0a6a35;font-weight:700;text-transform:uppercase;letter-spacing:0.04em}
.result .value{font-size:26px;font-weight:800;color:#0a3b5c;margin-top:4px}
.result .sub{font-size:13px;color:#3d5a78;margin-top:6px}

/* ---------- prose ---------- */
.prose h2{font-size:22px;margin:32px 0 10px;color:#0a3b5c;border-left:4px solid #f0a500;padding-left:12px}
.prose h3{font-size:18px;margin:24px 0 8px;color:#1d3a55}
.prose p{margin:0 0 14px}
.prose ul,.prose ol{margin:0 0 16px;padding-left:24px}
.prose li{margin-bottom:6px}
.prose table{width:100%;border-collapse:collapse;margin:14px 0 20px;font-size:14px;background:#fff}
.prose th,.prose td{border:1px solid #d8e3ee;padding:8px 12px;text-align:left}
.prose th{background:#eaf3fa;color:#0a3b5c}
.prose tr:nth-child(even) td{background:#fafcfe}
.callout{
  background:#fff5dd;border-left:4px solid #f0a500;padding:14px 16px;margin:18px 0;
  border-radius:0 8px 8px 0;font-size:15px;
}
.callout strong{color:#0a3b5c}
.fact-card{
  background:#eaf3fa;border:1px solid #cfdfeb;border-radius:10px;
  padding:14px 16px;margin:14px 0;
}
.fact-card .small{font-size:12px;color:#5a7794;text-transform:uppercase;letter-spacing:0.05em;font-weight:700}
.fact-card .big{font-size:22px;font-weight:800;color:#0a3b5c}

/* ---------- sidebar ---------- */
aside.sidebar{font-size:14px}
aside .panel{
  background:#fff;border:1px solid #cddeec;border-radius:12px;padding:16px 18px;margin-bottom:18px;
}
aside .panel h3{margin:0 0 10px;font-size:15px;color:#0a3b5c;text-transform:uppercase;letter-spacing:0.04em}
aside .panel ul{list-style:none;padding:0;margin:0}
aside .panel li{padding:6px 0;border-bottom:1px dashed #e3ecf3}
aside .panel li:last-child{border-bottom:0}

/* ---------- FAQ ---------- */
.faq{margin:24px 0}
.faq details{
  background:#fff;border:1px solid #d8e3ee;border-radius:10px;padding:0;margin-bottom:10px;
}
.faq summary{
  cursor:pointer;padding:14px 18px;font-weight:600;color:#0a3b5c;list-style:none;
  display:flex;justify-content:space-between;align-items:center;
}
.faq summary::after{content:"+";font-size:20px;font-weight:300;color:#0e7ab5}
.faq details[open] summary::after{content:"–"}
.faq details > div{padding:0 18px 16px;color:#243f5a}

/* ---------- footer ---------- */
footer{
  background:#0a3b5c;color:#c5d6e3;padding:28px 0 18px;margin-top:40px;
}
footer .wrap-f{max-width:1200px;margin:0 auto;padding:0 20px;display:flex;justify-content:space-between;gap:20px;flex-wrap:wrap}
footer h4{color:#fff;margin:0 0 8px;font-size:14px;text-transform:uppercase;letter-spacing:0.06em}
footer a{color:#c5d6e3;display:block;padding:3px 0;font-size:14px}
footer a:hover{color:#fff}
footer .legal{border-top:1px solid #1d4d77;margin-top:18px;padding-top:14px;text-align:center;font-size:12px;color:#7a98b2}