/* VO2max.io — dark sporty theme */
:root {
  --bg: #0b1220;
  --bg-elev: #121a2b;
  --bg-card: #162033;
  --line: rgba(148, 163, 184, 0.18);
  --text: #e8eef7;
  --muted: #9aa8bd;
  --accent: #2dd4bf;
  --accent-2: #38bdf8;
  --accent-dim: rgba(45, 212, 191, 0.14);
  --warn: #fbbf24;
  --danger: #f87171;
  --ok: #34d399;
  --radius: 14px;
  --shadow: 0 18px 50px rgba(0,0,0,.35);
  --font: "Segoe UI", system-ui, -apple-system, BlinkMacSystemFont, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font);
  background:
    radial-gradient(1200px 600px at 10% -10%, rgba(45,212,191,.16), transparent 55%),
    radial-gradient(900px 500px at 100% 0%, rgba(56,189,248,.12), transparent 50%),
    var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
}
img, svg { max-width: 100%; display: block; }
a { color: var(--accent-2); text-decoration-thickness: .08em; text-underline-offset: .18em; }
a:hover { color: var(--accent); }
.wrap { width: min(1100px, calc(100% - 2rem)); margin-inline: auto; }
.narrow { width: min(760px, calc(100% - 2rem)); }
.skip {
  position: absolute; left: -9999px; top: 0; background: var(--accent); color: #042f2e;
  padding: .6rem 1rem; z-index: 100; border-radius: 0 0 8px 0; font-weight: 700;
}
.skip:focus { left: 0; }
.site-header {
  position: sticky; top: 0; z-index: 40;
  backdrop-filter: blur(14px);
  background: rgba(11,18,32,.82);
  border-bottom: 1px solid var(--line);
}
.nav-wrap {
  display: flex; align-items: center; justify-content: space-between;
  gap: 1rem; min-height: 64px;
}
.brand {
  display: inline-flex; align-items: center; gap: .6rem;
  color: var(--text); text-decoration: none; font-weight: 800; letter-spacing: -.02em;
}
.brand-mark {
  width: 28px; height: 28px; border-radius: 9px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  box-shadow: 0 0 0 3px rgba(45,212,191,.18);
}
.brand-dot { color: var(--accent); font-weight: 700; }
.site-nav { display: flex; align-items: center; gap: .15rem 1rem; flex-wrap: wrap; }
.site-nav a {
  color: var(--muted); text-decoration: none; font-size: .92rem; font-weight: 600;
  padding: .35rem 0;
}
.site-nav a:hover, .site-nav a.active { color: var(--text); }
.nav-cta {
  background: linear-gradient(135deg, var(--accent), #14b8a6);
  color: #042f2e !important; padding: .55rem .95rem !important; border-radius: 999px;
  font-weight: 800 !important;
}
.nav-cta:hover { filter: brightness(1.05); }
.nav-toggle {
  display: none; background: transparent; border: 1px solid var(--line);
  border-radius: 10px; width: 44px; height: 44px; padding: 10px; cursor: pointer;
}
.nav-toggle span {
  display: block; height: 2px; background: var(--text); margin: 5px 0; border-radius: 2px;
}
@media (max-width: 860px) {
  .nav-toggle { display: inline-block; }
  .site-nav {
    display: none; position: absolute; left: 0; right: 0; top: 64px;
    background: var(--bg-elev); border-bottom: 1px solid var(--line);
    padding: 1rem 1rem 1.25rem; flex-direction: column; align-items: stretch;
  }
  .site-nav.open { display: flex; }
  .nav-cta { text-align: center; }
}
.hero {
  padding: 3.5rem 0 2.5rem;
}
.hero-grid {
  display: grid; gap: 2rem; align-items: center;
  grid-template-columns: 1.2fr .8fr;
}
@media (max-width: 860px) { .hero-grid { grid-template-columns: 1fr; } }
.eyebrow {
  display: inline-block; color: var(--accent); font-weight: 700; font-size: .78rem;
  letter-spacing: .08em; text-transform: uppercase; margin: 0 0 .75rem;
}
h1 {
  font-size: clamp(1.9rem, 4vw, 3rem); line-height: 1.15; letter-spacing: -.03em;
  margin: 0 0 1rem;
}
h1 span { color: var(--accent); }
.lead, .hero-copy { color: var(--muted); font-size: 1.08rem; max-width: 42rem; }
.hero-actions { display: flex; flex-wrap: wrap; gap: .75rem; margin-top: 1.5rem; }
.button, button.button {
  display: inline-flex; align-items: center; justify-content: center; gap: .4rem;
  background: linear-gradient(135deg, var(--accent), #14b8a6);
  color: #042f2e; font-weight: 800; border: 0; border-radius: 999px;
  padding: .85rem 1.25rem; text-decoration: none; cursor: pointer; font-size: 1rem;
}
.button:hover { filter: brightness(1.05); color: #042f2e; }
.button.secondary {
  background: transparent; color: var(--text);
  border: 1px solid var(--line);
}
.button.secondary:hover { border-color: var(--accent); color: var(--accent); }
.button.small { padding: .55rem .9rem; font-size: .9rem; }
.hero-card {
  background: linear-gradient(180deg, rgba(45,212,191,.12), rgba(22,32,51,.9));
  border: 1px solid var(--line); border-radius: calc(var(--radius) + 4px);
  padding: 1.25rem; box-shadow: var(--shadow);
}
.stat-row { display: grid; grid-template-columns: repeat(3, 1fr); gap: .75rem; margin-top: 1rem; }
.stat {
  background: rgba(11,18,32,.55); border: 1px solid var(--line); border-radius: 12px; padding: .85rem;
  text-align: center;
}
.stat strong { display: block; font-size: 1.25rem; color: var(--accent); }
.stat span { color: var(--muted); font-size: .78rem; }
.section { padding: 2.5rem 0; }
.section.alt { background: rgba(18,26,43,.55); border-block: 1px solid var(--line); }
.section h2 { font-size: clamp(1.35rem, 2.5vw, 1.8rem); letter-spacing: -.02em; margin: 0 0 .75rem; }
.card-grid {
  display: grid; gap: 1rem;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  margin-top: 1.25rem;
}
.card {
  background: var(--bg-card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 1.15rem 1.2rem; text-decoration: none; color: inherit;
  transition: border-color .15s ease, transform .15s ease;
}
a.card:hover { border-color: var(--accent); transform: translateY(-2px); }
.card h3 { margin: 0 0 .4rem; font-size: 1.05rem; }
.card p { margin: 0; color: var(--muted); font-size: .95rem; }
.page-hero { padding: 2.75rem 0 1.25rem; }
.prose p, .prose li { color: var(--muted); }
.prose h2 { margin-top: 2rem; }
.prose ul, .prose ol { padding-left: 1.2rem; }
.prose li { margin: .4rem 0; }
.callout {
  background: var(--accent-dim); border: 1px solid rgba(45,212,191,.35);
  border-radius: var(--radius); padding: 1rem 1.15rem; margin: 1.25rem 0;
}
.callout.warn {
  background: rgba(251,191,36,.1); border-color: rgba(251,191,36,.35);
}
.callout strong { color: var(--text); }
.formula {
  font-family: var(--mono); background: #0a101c; border: 1px solid var(--line);
  border-radius: 10px; padding: .85rem 1rem; overflow-x: auto; color: var(--accent);
  font-size: .95rem;
}
.table-wrap { overflow-x: auto; margin: 1rem 0; }
table {
  width: 100%; border-collapse: collapse; font-size: .92rem;
  background: var(--bg-card); border-radius: 12px; overflow: hidden;
}
th, td { padding: .65rem .75rem; border-bottom: 1px solid var(--line); text-align: left; }
th { color: var(--text); background: rgba(0,0,0,.2); }
td { color: var(--muted); }
.site-footer {
  margin-top: 2rem; border-top: 1px solid var(--line);
  background: #070c16; padding: 2.5rem 0 2rem;
}
.footer-grid {
  display: grid; gap: 1.5rem;
  grid-template-columns: 1.4fr repeat(3, 1fr);
}
@media (max-width: 800px) { .footer-grid { grid-template-columns: 1fr 1fr; } }
@media (max-width: 520px) { .footer-grid { grid-template-columns: 1fr; } }
.footer-grid h2 { font-size: .78rem; text-transform: uppercase; letter-spacing: .08em; color: var(--muted); margin: 0 0 .6rem; }
.footer-grid a { display: block; color: var(--text); text-decoration: none; margin: .3rem 0; font-size: .95rem; }
.footer-grid a:hover { color: var(--accent); }
.footer-tag { color: var(--muted); font-size: .92rem; }
.footer-brand { margin-bottom: .5rem; }
.footer-bottom { margin-top: 2rem; padding-top: 1.25rem; border-top: 1px solid var(--line); }
.disclaimer, .company-details, .copy { color: var(--muted); font-size: .85rem; font-style: normal; }
.company-details { margin: .75rem 0; line-height: 1.55; }
.disclosure { font-size: .9rem; color: var(--muted); }
.ad-slot {
  min-height: 90px; margin: 1.5rem auto; max-width: 728px;
  border: 1px dashed var(--line); border-radius: 10px;
  display: flex; align-items: center; justify-content: center; color: var(--muted); font-size: .8rem;
}

/* Calculator */
.calc-shell {
  background: var(--bg-elev); border: 1px solid var(--line); border-radius: calc(var(--radius) + 4px);
  box-shadow: var(--shadow); overflow: hidden;
}
.calc-tabs {
  display: flex; flex-wrap: wrap; gap: .35rem; padding: .85rem;
  background: rgba(0,0,0,.25); border-bottom: 1px solid var(--line);
}
.calc-tabs button {
  flex: 1 1 auto; min-width: 140px; border: 1px solid transparent; background: transparent;
  color: var(--muted); border-radius: 999px; padding: .65rem .9rem; font-weight: 700;
  cursor: pointer; font-size: .9rem;
}
.calc-tabs button[aria-selected="true"] {
  background: var(--accent-dim); color: var(--accent); border-color: rgba(45,212,191,.35);
}
.calc-body { display: grid; grid-template-columns: 1.05fr .95fr; gap: 0; }
@media (max-width: 860px) { .calc-body { grid-template-columns: 1fr; } }
.calc-form, .calc-result { padding: 1.25rem 1.35rem 1.5rem; }
.calc-result { background: rgba(45,212,191,.06); border-left: 1px solid var(--line); }
@media (max-width: 860px) { .calc-result { border-left: 0; border-top: 1px solid var(--line); } }
.field { margin-bottom: 1rem; }
.field label { display: block; font-weight: 700; font-size: .9rem; margin-bottom: .35rem; }
.field .hint { display: block; color: var(--muted); font-size: .8rem; margin-top: .3rem; }
.field-row { display: grid; grid-template-columns: 1fr 1fr; gap: .75rem; }
@media (max-width: 520px) { .field-row { grid-template-columns: 1fr; } }
input[type="number"], select, input[type="text"] {
  width: 100%; background: #0a101c; border: 1px solid var(--line); color: var(--text);
  border-radius: 10px; padding: .75rem .85rem; font-size: 1rem;
}
input:focus, select:focus, button:focus-visible, a:focus-visible {
  outline: 2px solid var(--accent); outline-offset: 2px;
}
.unit-toggle {
  display: inline-flex; background: #0a101c; border: 1px solid var(--line); border-radius: 999px; padding: 3px;
}
.unit-toggle button {
  border: 0; background: transparent; color: var(--muted); border-radius: 999px;
  padding: .4rem .75rem; font-weight: 700; cursor: pointer;
}
.unit-toggle button[aria-pressed="true"] { background: var(--accent); color: #042f2e; }
.result-value {
  font-size: clamp(2.4rem, 6vw, 3.4rem); font-weight: 900; letter-spacing: -.04em;
  color: var(--accent); line-height: 1;
}
.result-unit { color: var(--muted); font-weight: 600; font-size: 1rem; }
.result-category {
  display: inline-block; margin-top: .85rem; padding: .35rem .7rem; border-radius: 999px;
  background: rgba(56,189,248,.15); color: var(--accent-2); font-weight: 800; font-size: .85rem;
}
.zones { margin-top: 1.1rem; display: grid; gap: .45rem; }
.zone {
  display: grid; grid-template-columns: 52px 1fr auto; gap: .6rem; align-items: center;
  background: rgba(11,18,32,.45); border: 1px solid var(--line); border-radius: 10px; padding: .55rem .7rem;
}
.zone b { color: var(--text); }
.zone span { color: var(--muted); font-size: .85rem; }
.zone i { font-style: normal; font-family: var(--mono); color: var(--accent); font-size: .85rem; }
details.how {
  margin-top: 1rem; border: 1px solid var(--line); border-radius: 12px; padding: .7rem .9rem;
  background: rgba(11,18,32,.35);
}
details.how summary { cursor: pointer; font-weight: 700; }
.cta-row { display: flex; flex-wrap: wrap; gap: .6rem; margin-top: 1.1rem; }
.muted { color: var(--muted); }
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0;
}