/* BioCalc — clean modern lab design system */
:root{
  --bg:#f6f8f9;
  --surface:#ffffff;
  --surface-2:#eef3f4;
  --border:#dbe3e6;
  --border-strong:#c3d0d4;
  --text:#16232b;
  --text-2:#4d6069;
  --text-3:#7b8f98;
  --accent:#0d7a6f;
  --accent-dark:#095e55;
  --accent-soft:#e3f3f0;
  --accent-2:#1f5f8b;
  --warn:#b45309;
  --warn-soft:#fdf3e3;
  --danger:#b3261e;
  --radius:10px;
  --radius-sm:6px;
  --shadow:0 1px 2px rgba(16,40,50,.05), 0 4px 14px rgba(16,40,50,.05);
  --shadow-lg:0 2px 6px rgba(16,40,50,.06), 0 12px 32px rgba(16,40,50,.09);
  --mono:"SFMono-Regular",ui-monospace,"JetBrains Mono",Menlo,Consolas,monospace;
  --sans:-apple-system,BlinkMacSystemFont,"Segoe UI","Inter",Roboto,"Helvetica Neue",Arial,sans-serif;
  --maxw:1120px;
}

*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%}
body{
  margin:0;background:var(--bg);color:var(--text);
  font-family:var(--sans);font-size:16px;line-height:1.6;
  -webkit-font-smoothing:antialiased;
}
a{color:var(--accent);text-decoration:none}
a:hover{text-decoration:underline}
h1,h2,h3,h4{line-height:1.25;margin:0 0 .5em;font-weight:650;letter-spacing:-.011em}
h1{font-size:2rem}
h2{font-size:1.3rem}
h3{font-size:1.05rem}
p{margin:0 0 1em}
code,kbd{font-family:var(--mono);font-size:.9em;background:var(--surface-2);padding:.1em .35em;border-radius:4px}
.wrap{max-width:var(--maxw);margin:0 auto;padding:0 20px}

/* ---------- Header ---------- */
.site-header{background:var(--surface);border-bottom:1px solid var(--border);position:sticky;top:0;z-index:50}
.header-inner{display:flex;align-items:center;gap:20px;height:60px}
.brand{display:flex;align-items:center;gap:9px;font-weight:700;font-size:1.05rem;color:var(--text);letter-spacing:-.02em}
.brand:hover{text-decoration:none}
.brand-mark{width:26px;height:26px;flex:none}
.brand small{display:block;font-weight:450;font-size:.68rem;color:var(--text-3);letter-spacing:.02em;line-height:1}
.nav{margin-left:auto;display:flex;gap:2px;flex-wrap:wrap}
.nav a{
  padding:7px 11px;border-radius:var(--radius-sm);font-size:.88rem;
  color:var(--text-2);font-weight:500;white-space:nowrap;
}
.nav a:hover{background:var(--surface-2);color:var(--text);text-decoration:none}
.nav a[aria-current="page"]{background:var(--accent-soft);color:var(--accent-dark);font-weight:600}
.nav-toggle{display:none;margin-left:auto;background:var(--surface-2);border:1px solid var(--border);
  border-radius:var(--radius-sm);padding:7px 11px;font:inherit;font-size:.85rem;cursor:pointer;color:var(--text)}
@media(max-width:900px){
  .nav-toggle{display:block}
  .nav{display:none;position:absolute;top:60px;left:0;right:0;background:var(--surface);
    border-bottom:1px solid var(--border);flex-direction:column;padding:8px 16px 14px;gap:0;box-shadow:var(--shadow)}
  .nav.open{display:flex}
  .nav a{padding:10px 8px}
}

/* ---------- Layout ---------- */
main{padding:32px 0 56px}
.page-head{margin-bottom:26px;max-width:760px}
.page-head .eyebrow{font-size:.75rem;text-transform:uppercase;letter-spacing:.09em;color:var(--accent);font-weight:700;margin-bottom:6px}
.page-head p.lede{font-size:1.03rem;color:var(--text-2);margin-bottom:0}
.grid{display:grid;gap:20px}
@media(min-width:820px){ .grid.cols-2{grid-template-columns:1fr 1fr} }

/* ---------- Cards ---------- */
.card{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);
  box-shadow:var(--shadow);padding:20px 22px 22px;margin-bottom:20px}
.card > h2{display:flex;align-items:baseline;gap:9px;font-size:1.13rem;margin-bottom:4px}
.card > h2 .tag{font-size:.68rem;font-weight:700;text-transform:uppercase;letter-spacing:.07em;
  color:var(--accent-dark);background:var(--accent-soft);padding:2px 7px;border-radius:20px}
.card .hint{color:var(--text-2);font-size:.9rem;margin-bottom:16px}
.card .formula{font-family:var(--mono);font-size:.85rem;color:var(--text-2);
  background:var(--surface-2);border-left:3px solid var(--border-strong);
  padding:8px 12px;border-radius:0 var(--radius-sm) var(--radius-sm) 0;margin:0 0 16px;overflow-x:auto;white-space:nowrap}

/* ---------- Forms ---------- */
.field{margin-bottom:14px}
.field > label,.field-label{display:block;font-size:.83rem;font-weight:600;color:var(--text-2);margin-bottom:5px}
.field-label .opt{font-weight:400;color:var(--text-3)}
.row{display:flex;gap:8px;align-items:stretch;flex-wrap:wrap}
.row > .field{flex:1 1 150px;margin-bottom:0}
.field-row{margin-bottom:14px}
input[type=number],input[type=text],select,textarea{
  width:100%;padding:9px 11px;font:inherit;font-size:.95rem;color:var(--text);
  background:var(--surface);border:1px solid var(--border-strong);border-radius:var(--radius-sm);
  transition:border-color .12s, box-shadow .12s;
}
input[type=number],.num{font-family:var(--mono);font-variant-numeric:tabular-nums}
textarea{font-family:var(--mono);font-size:.85rem;line-height:1.5;resize:vertical}
input:focus,select:focus,textarea:focus{outline:none;border-color:var(--accent);box-shadow:0 0 0 3px var(--accent-soft)}
input[readonly]{background:var(--surface-2);color:var(--text-2)}
select{appearance:none;background-image:url("data:image/svg+xml;charset=utf-8,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 12 12'%3E%3Cpath fill='%234d6069' d='M2.5 4.5L6 8l3.5-3.5z'/%3E%3C/svg%3E");
  background-repeat:no-repeat;background-position:right 8px center;background-size:12px;padding-right:28px;cursor:pointer}
.combo{display:flex;gap:0}
.combo input{border-top-right-radius:0;border-bottom-right-radius:0;flex:1 1 auto;min-width:0}
.combo select{border-top-left-radius:0;border-bottom-left-radius:0;border-left:none;flex:0 0 auto;width:auto;min-width:92px;background-color:var(--surface-2)}
.combo input:focus + select{border-left-color:var(--accent)}
fieldset{border:none;margin:0;padding:0}
.radios{display:flex;gap:6px;flex-wrap:wrap;margin-bottom:14px}
.radios label{
  display:inline-flex;align-items:center;gap:6px;font-size:.86rem;color:var(--text-2);
  border:1px solid var(--border-strong);background:var(--surface);padding:6px 11px;border-radius:20px;cursor:pointer;
  transition:all .12s;
}
.radios label:hover{border-color:var(--accent)}
.radios input{margin:0;accent-color:var(--accent)}
.radios input:checked + span{color:var(--accent-dark);font-weight:600}
.radios label:has(input:checked){background:var(--accent-soft);border-color:var(--accent)}

button,.btn{
  font:inherit;font-size:.92rem;font-weight:600;cursor:pointer;border-radius:var(--radius-sm);
  padding:9px 16px;border:1px solid transparent;transition:background .12s,border-color .12s;
}
.btn-primary{background:var(--accent);color:#fff}
.btn-primary:hover{background:var(--accent-dark)}
.btn-ghost{background:var(--surface);color:var(--text-2);border-color:var(--border-strong)}
.btn-ghost:hover{background:var(--surface-2);color:var(--text)}
.btn-row{display:flex;gap:8px;flex-wrap:wrap;margin-top:16px}

/* ---------- Results ---------- */
.result{
  background:var(--accent-soft);border:1px solid #bfe0da;border-radius:var(--radius);
  padding:14px 16px;margin-top:16px;
}
.result.empty{background:var(--surface-2);border-color:var(--border);color:var(--text-3)}
.result-main{font-family:var(--mono);font-size:1.32rem;font-weight:600;color:var(--accent-dark);
  letter-spacing:-.01em;word-break:break-word;line-height:1.35}
.result.empty .result-main{font-size:.92rem;font-family:var(--sans);font-weight:400;color:var(--text-3)}
.result-sub{font-size:.85rem;color:var(--text-2);margin-top:6px}
.result-sub span{display:inline-block;margin-right:14px;font-family:var(--mono)}
.result-steps{margin-top:10px;padding-top:10px;border-top:1px dashed #bfe0da;
  font-family:var(--mono);font-size:.78rem;color:var(--text-2);line-height:1.7;white-space:pre-wrap}
.err{background:#fdecea;border-color:#f3c4bf;color:var(--danger)}
.err .result-main{color:var(--danger);font-size:.95rem;font-family:var(--sans);font-weight:500}

/* ---------- Tables ---------- */
.table-scroll{overflow-x:auto;margin:0 0 16px;border:1px solid var(--border);border-radius:var(--radius)}
table{border-collapse:collapse;width:100%;font-size:.88rem}
th,td{text-align:left;padding:9px 12px;border-bottom:1px solid var(--border)}
thead th{background:var(--surface-2);font-size:.76rem;text-transform:uppercase;letter-spacing:.05em;
  color:var(--text-2);font-weight:700;white-space:nowrap}
tbody tr:last-child td{border-bottom:none}
tbody tr:hover{background:#fafcfc}
td.num,th.num{font-family:var(--mono);font-variant-numeric:tabular-nums;text-align:right}

/* ---------- Hub / index ---------- */
.hero{background:linear-gradient(180deg,#ffffff,#f2f7f7);border-bottom:1px solid var(--border);padding:44px 0 40px}
.hero h1{font-size:2.35rem;max-width:16ch;margin-bottom:12px}
.hero p{font-size:1.08rem;color:var(--text-2);max-width:62ch;margin-bottom:0}
.hero .kicker{font-size:.75rem;text-transform:uppercase;letter-spacing:.1em;color:var(--accent);font-weight:700;margin-bottom:10px}
.tool-grid{display:grid;gap:16px;grid-template-columns:repeat(auto-fill,minmax(268px,1fr))}
.tool{display:block;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);
  padding:18px 18px 16px;box-shadow:var(--shadow);transition:transform .13s,box-shadow .13s,border-color .13s;color:var(--text)}
.tool:hover{text-decoration:none;transform:translateY(-2px);box-shadow:var(--shadow-lg);border-color:var(--border-strong)}
.tool h3{margin-bottom:5px;font-size:1rem;color:var(--accent-dark)}
.tool p{font-size:.88rem;color:var(--text-2);margin:0}
.tool ul{margin:9px 0 0;padding:0;list-style:none;display:flex;flex-wrap:wrap;gap:5px}
.tool ul li{font-size:.72rem;background:var(--surface-2);color:var(--text-2);padding:2px 7px;border-radius:20px}

/* ---------- Prose / FAQ ---------- */
.prose{max-width:72ch}
.prose h2{margin-top:1.6em}
.prose ul,.prose ol{padding-left:1.25em}
.prose li{margin-bottom:.35em}
details.faq{border:1px solid var(--border);border-radius:var(--radius);background:var(--surface);
  padding:0;margin-bottom:8px;overflow:hidden}
details.faq summary{cursor:pointer;padding:13px 16px;font-weight:600;font-size:.95rem;list-style:none}
details.faq summary::-webkit-details-marker{display:none}
details.faq summary::before{content:"+";display:inline-block;width:1.1em;color:var(--accent);font-weight:700}
details.faq[open] summary::before{content:"\2212"}
details.faq .faq-body{padding:0 16px 14px 16px;color:var(--text-2);font-size:.93rem}
details.faq .faq-body p:last-child{margin-bottom:0}

.note{background:var(--warn-soft);border:1px solid #f0dcb8;border-radius:var(--radius);
  padding:12px 15px;font-size:.88rem;color:#7c4a08;margin-bottom:16px}
.note strong{color:#5f3806}

.related{display:flex;gap:8px;flex-wrap:wrap;margin-top:8px}
.related a{font-size:.85rem;background:var(--surface);border:1px solid var(--border-strong);
  padding:6px 12px;border-radius:20px;color:var(--text-2)}
.related a:hover{border-color:var(--accent);color:var(--accent-dark);text-decoration:none}

/* ---------- Footer ---------- */
.site-footer{border-top:1px solid var(--border);background:var(--surface);padding:30px 0 40px;margin-top:20px}
.footer-grid{display:grid;gap:24px;grid-template-columns:repeat(auto-fit,minmax(180px,1fr));margin-bottom:22px}
.footer-grid h4{font-size:.76rem;text-transform:uppercase;letter-spacing:.07em;color:var(--text-3);margin-bottom:9px}
.footer-grid ul{list-style:none;margin:0;padding:0}
.footer-grid li{margin-bottom:5px}
.footer-grid a{font-size:.88rem;color:var(--text-2)}
.footer-grid a:hover{color:var(--accent)}
.footer-base{border-top:1px solid var(--border);padding-top:16px;font-size:.83rem;color:var(--text-3);
  display:flex;justify-content:space-between;gap:14px;flex-wrap:wrap}

/* ---------- Ad slots (only rendered when advertising is enabled) ---------- */
.ad-slot{
  display:block;margin:26px 0;padding:10px 0;
  border-top:1px solid var(--border);border-bottom:1px solid var(--border);
  min-height:100px;text-align:center;background:transparent;
}
.ad-slot .ad-label{
  display:block;font-size:.64rem;text-transform:uppercase;letter-spacing:.09em;
  color:var(--text-3);margin-bottom:8px;
}
.ad-slot ins{margin:0 auto}
@media print{.ad-slot{display:none}}

.skip{position:absolute;left:-9999px;top:0;background:var(--accent);color:#fff;padding:10px 16px;z-index:100}
.skip:focus{left:0}

@media print{.site-header,.site-footer,.btn-row,.nav{display:none}.card{break-inside:avoid;box-shadow:none}}