/* TradeReady — 313A prep course site. Working brand name is a PLACEHOLDER
   pending legal review of "Red Seal" usage (see vault/.../hvac-course-aggregator.md). */

:root {
  --bg: #f5f8fc;
  --surface: #ffffff;
  --surface-2: #eef3fa;
  --border: #dbe4ef;
  --ink: #0f2033;
  --ink-2: #47586b;
  --brand: #0b5cad;      /* trust blue */
  --brand-dark: #084684;
  --cold: #2b8fd6;       /* low side */
  --heat: #ef7a2b;       /* high side */
  --good: #1f9d55;
  --bad: #d64545;
  --shadow: 0 1px 2px rgba(15,32,51,.06), 0 8px 24px rgba(15,32,51,.06);
  --radius: 14px;
  --maxw: 1120px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0c1420; --surface: #121c2b; --surface-2: #16233650; --border: #23324a;
    --ink: #eaf1fa; --ink-2: #9fb2c9; --brand: #3a8ee6; --brand-dark: #2b6fbb;
    --shadow: 0 1px 2px rgba(0,0,0,.3), 0 10px 30px rgba(0,0,0,.35);
  }
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg); color: var(--ink); line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--brand); text-decoration: none; }
a:hover { text-decoration: underline; }
img, svg { max-width: 100%; }
.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }
.muted { color: var(--ink-2); }
.center { text-align: center; }

/* ---- Header ---- */
header.site {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(1.2) blur(10px);
  border-bottom: 1px solid var(--border);
}
.nav { display: flex; align-items: center; gap: 18px; height: 62px; }
.brand { display: flex; align-items: center; gap: 9px; font-weight: 800; font-size: 1.12rem; color: var(--ink); }
.brand:hover { text-decoration: none; }
.brand .dot { width: 22px; height: 22px; border-radius: 6px;
  background: linear-gradient(135deg, var(--cold), var(--heat)); display: inline-block; }
.brand small { font-weight: 600; color: var(--ink-2); font-size: .72rem; letter-spacing: .04em; }
.nav .spacer { flex: 1; }
.nav .links { display: flex; gap: 20px; align-items: center; }
.nav .links a { color: var(--ink-2); font-weight: 600; font-size: .93rem; }
.nav .links a:hover { color: var(--ink); text-decoration: none; }
.nav-toggle { display: none; background: none; border: 1px solid var(--border);
  border-radius: 8px; padding: 6px 9px; color: var(--ink); font-size: 1.1rem; }
@media (max-width: 820px) {
  .nav .links { display: none; position: absolute; top: 62px; left: 0; right: 0;
    flex-direction: column; gap: 0; background: var(--surface); border-bottom: 1px solid var(--border); }
  .nav .links.open { display: flex; }
  .nav .links a { padding: 14px 20px; border-top: 1px solid var(--border); }
  .nav .links .btn { margin: 12px 20px; text-align: center; }
  .nav-toggle { display: block; }
}

/* ---- Buttons ---- */
.btn { display: inline-flex; align-items: center; gap: 8px; font-weight: 700;
  padding: 12px 20px; border-radius: 10px; border: 1px solid transparent; cursor: pointer;
  font-size: .98rem; transition: transform .05s ease, background .15s ease; }
.btn:hover { text-decoration: none; }
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--brand); color: #fff; }
.btn-primary:hover { background: var(--brand-dark); color: #fff; }
.btn-ghost { background: var(--surface); color: var(--ink); border-color: var(--border); }
.btn-ghost:hover { background: var(--surface-2); }
.btn-lg { padding: 15px 26px; font-size: 1.05rem; }

/* ---- Layout bits ---- */
section { padding: 64px 0; }
.eyebrow { text-transform: uppercase; letter-spacing: .12em; font-size: .78rem;
  font-weight: 800; color: var(--brand); }
h1 { font-size: clamp(2rem, 5vw, 3.1rem); line-height: 1.08; letter-spacing: -.02em; font-weight: 850; }
h2 { font-size: clamp(1.5rem, 3.5vw, 2.1rem); letter-spacing: -.01em; font-weight: 820; }
h3 { font-size: 1.18rem; font-weight: 750; }
.lead { font-size: 1.18rem; color: var(--ink-2); }
.grid { display: grid; gap: 20px; }
.cols-3 { grid-template-columns: repeat(3, 1fr); }
.cols-2 { grid-template-columns: repeat(2, 1fr); }
.cols-4 { grid-template-columns: repeat(4, 1fr); }
@media (max-width: 900px){ .cols-3,.cols-4 { grid-template-columns: 1fr 1fr; } }
@media (max-width: 640px){ .cols-2,.cols-3,.cols-4 { grid-template-columns: 1fr; } }

.card { background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 22px; box-shadow: var(--shadow); }
.card h3 { margin-bottom: 6px; }
.pill { display: inline-block; background: var(--surface-2); color: var(--ink-2);
  border: 1px solid var(--border); border-radius: 999px; padding: 4px 12px; font-size: .8rem; font-weight: 700; }
.badge-free { background: color-mix(in srgb, var(--good) 15%, transparent);
  color: var(--good); border-color: color-mix(in srgb, var(--good) 35%, transparent); }

/* ---- Hero ---- */
.hero { padding: 72px 0 40px; }
.hero-grid { display: grid; grid-template-columns: 1.05fr .95fr; gap: 40px; align-items: center; }
@media (max-width: 900px){ .hero-grid { grid-template-columns: 1fr; } }
.stat-row { display: flex; gap: 26px; flex-wrap: wrap; margin-top: 8px; }
.stat b { font-size: 1.5rem; display: block; color: var(--ink); }
.stat span { font-size: .85rem; color: var(--ink-2); }

/* ---- Weight bars (exam breakdown) ---- */
.bars { display: grid; gap: 10px; }
.bar-row { display: grid; grid-template-columns: 220px 1fr 48px; align-items: center; gap: 12px; }
@media (max-width:640px){ .bar-row { grid-template-columns: 1fr; gap: 4px; } }
.bar-track { background: var(--surface-2); border-radius: 999px; height: 14px; overflow: hidden; border: 1px solid var(--border); }
.bar-fill { height: 100%; background: linear-gradient(90deg, var(--cold), var(--brand)); border-radius: 999px;
  width: 0; transition: width 1s cubic-bezier(.2,.7,.3,1); }
.bar-row.hot .bar-fill { background: linear-gradient(90deg, var(--brand), var(--heat)); }
.bar-val { font-weight: 800; text-align: right; }

/* ---- Refrigeration cycle diagram ---- */
.cycle-wrap { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px; box-shadow: var(--shadow); }
.cycle-legend { display: flex; gap: 18px; justify-content: center; margin-bottom: 6px; flex-wrap: wrap; font-size: .85rem; font-weight: 700; }
.legend-dot { display: inline-block; width: 12px; height: 12px; border-radius: 3px; vertical-align: middle; margin-right: 6px; }
.stage-btns { display: flex; gap: 8px; flex-wrap: wrap; justify-content: center; margin-top: 12px; }
.stage-btn { border: 1px solid var(--border); background: var(--surface); color: var(--ink-2);
  border-radius: 8px; padding: 8px 14px; font-weight: 700; cursor: pointer; font-size: .88rem; }
.stage-btn.active { background: var(--brand); color: #fff; border-color: var(--brand); }
.stage-info { margin-top: 14px; background: var(--surface-2); border: 1px solid var(--border);
  border-radius: 10px; padding: 16px; min-height: 92px; }
.stage-info h4 { font-size: 1.05rem; margin-bottom: 4px; }
.moving-dot { fill: #fff; stroke: var(--ink); stroke-width: 1.5; }

/* ---- Quiz ---- */
.quiz { display: grid; gap: 18px; }
.q { background: var(--surface); border: 1px solid var(--border); border-radius: 12px; padding: 18px; }
.q .stem { font-weight: 700; margin-bottom: 12px; }
.opt { display: block; border: 1px solid var(--border); border-radius: 9px; padding: 11px 14px;
  margin-bottom: 8px; cursor: pointer; transition: background .12s; }
.opt:hover { background: var(--surface-2); }
.opt input { margin-right: 9px; }
.opt.correct { border-color: var(--good); background: color-mix(in srgb, var(--good) 12%, transparent); }
.opt.wrong { border-color: var(--bad); background: color-mix(in srgb, var(--bad) 12%, transparent); }
.rationale { margin-top: 8px; font-size: .9rem; color: var(--ink-2); display: none; }
.rationale.show { display: block; }
.quiz-result { font-size: 1.15rem; font-weight: 800; padding: 16px; border-radius: 12px;
  background: var(--surface-2); border: 1px solid var(--border); text-align: center; }

/* ---- Forms ---- */
.field { margin-bottom: 16px; }
.field label { display: block; font-weight: 700; margin-bottom: 6px; font-size: .92rem; }
.field input, .field select { width: 100%; padding: 12px 14px; border: 1px solid var(--border);
  border-radius: 10px; background: var(--surface); color: var(--ink); font-size: 1rem; }
.field input:focus, .field select:focus { outline: 2px solid var(--brand); border-color: var(--brand); }
.field .err { color: var(--bad); font-size: .84rem; margin-top: 4px; display: none; }
.field.invalid .err { display: block; }
.field.invalid input { border-color: var(--bad); }

/* ---- Paywall / CTA band ---- */
.band { background: linear-gradient(135deg, var(--brand), var(--brand-dark)); color: #fff; border-radius: var(--radius); padding: 34px; }
.band h2, .band .lead { color: #fff; }
.band .btn-ghost { background: rgba(255,255,255,.14); color: #fff; border-color: rgba(255,255,255,.35); }

.price-tag { font-size: 2.4rem; font-weight: 850; }
.price-tag small { font-size: 1rem; color: var(--ink-2); font-weight: 600; }

footer.site { border-top: 1px solid var(--border); padding: 30px 0; color: var(--ink-2); font-size: .9rem; }
.disclaim { background: color-mix(in srgb, var(--heat) 8%, transparent);
  border: 1px solid color-mix(in srgb, var(--heat) 30%, transparent); color: var(--ink-2);
  border-radius: 10px; padding: 12px 16px; font-size: .84rem; margin-top: 18px; }
.steps { counter-reset: s; display: grid; gap: 16px; }
.step { display: grid; grid-template-columns: 44px 1fr; gap: 16px; align-items: start; }
.step .n { counter-increment: s; width: 44px; height: 44px; border-radius: 12px; background: var(--surface-2);
  border: 1px solid var(--border); display: grid; place-items: center; font-weight: 850; color: var(--brand); }
.step .n::before { content: counter(s); }