/* OpenTencor AI — dark-tech theme */
:root {
  --bg: #070b14;
  --bg-soft: #0c1220;
  --surface: #101828;
  --surface-2: #16203a;
  --border: #1f2b45;
  --text: #e8eef7;
  --muted: #9aa7bf;
  --accent: #22d3ee;
  --accent-2: #a78bfa;
  --accent-dim: rgba(34, 211, 238, 0.12);
  --warn: #fbbf24;
  --radius: 14px;
  --maxw: 1080px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  line-height: 1.7;
  font-size: 17px;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.container { max-width: var(--maxw); margin: 0 auto; padding: 0 22px; }

/* ---------- Header ---------- */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: rgba(7, 11, 20, 0.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.header-inner {
  display: flex; align-items: center; justify-content: space-between;
  padding: 14px 22px; max-width: var(--maxw); margin: 0 auto;
}
.brand { display: flex; align-items: center; gap: 12px; color: var(--text); }
.brand:hover { text-decoration: none; }
.brand-name { font-weight: 800; font-size: 1.25rem; letter-spacing: 0.2px; }
.brand-name span { color: var(--accent); }

.nav-links { display: flex; gap: 26px; align-items: center; }
.nav-links a { color: var(--muted); font-weight: 600; font-size: 0.98rem; }
.nav-links a:hover, .nav-links a.active { color: var(--accent); text-decoration: none; }
.nav-cta {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  color: #04121a !important; padding: 8px 18px; border-radius: 999px; font-weight: 700 !important;
}
.nav-toggle { display: none; background: none; border: 1px solid var(--border); color: var(--text);
  border-radius: 10px; padding: 8px 12px; font-size: 1.1rem; cursor: pointer; }

/* ---------- Hero ---------- */
.hero {
  padding: 84px 0 64px;
  background:
    radial-gradient(900px 420px at 15% 0%, rgba(34, 211, 238, 0.10), transparent 60%),
    radial-gradient(800px 420px at 85% 10%, rgba(167, 139, 250, 0.10), transparent 60%),
    var(--bg);
  border-bottom: 1px solid var(--border);
}
.hero h1 { font-size: clamp(2rem, 5vw, 3.2rem); line-height: 1.15; margin: 0 0 18px; letter-spacing: -0.5px; }
.hero h1 .grad {
  background: linear-gradient(120deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero p.lead { font-size: 1.15rem; color: var(--muted); max-width: 680px; margin: 0 0 30px; }
.hero-actions { display: flex; gap: 14px; flex-wrap: wrap; }
.btn {
  display: inline-block; padding: 13px 28px; border-radius: 999px; font-weight: 700;
  background: linear-gradient(135deg, var(--accent), var(--accent-2)); color: #04121a; border: 0;
}
.btn:hover { text-decoration: none; filter: brightness(1.08); }
.btn-ghost {
  background: transparent; color: var(--accent); border: 1px solid var(--accent);
}
.btn-ghost:hover { background: var(--accent-dim); text-decoration: none; }

/* ---------- Cards ---------- */
.section { padding: 60px 0; }
.section h2 { font-size: 1.7rem; margin: 0 0 8px; letter-spacing: -0.3px; }
.section .sub { color: var(--muted); margin: 0 0 30px; max-width: 720px; }
.card-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(290px, 1fr)); gap: 20px; }
.card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 26px; transition: transform 0.15s ease, border-color 0.15s ease;
}
.card:hover { transform: translateY(-3px); border-color: var(--accent); }
.card h3 { margin: 0 0 10px; font-size: 1.15rem; }
.card h3 a { color: var(--text); }
.card h3 a:hover { color: var(--accent); text-decoration: none; }
.card p { color: var(--muted); font-size: 0.97rem; margin: 0 0 14px; }
.card .tag {
  display: inline-block; font-size: 0.75rem; font-weight: 700; letter-spacing: 0.6px;
  text-transform: uppercase; color: var(--accent); background: var(--accent-dim);
  padding: 4px 10px; border-radius: 999px; margin-bottom: 12px;
}
.card .read-more { font-weight: 700; font-size: 0.95rem; }

/* ---------- Article ---------- */
.article { max-width: 780px; margin: 0 auto; }
.article h1 { font-size: clamp(1.8rem, 4vw, 2.6rem); line-height: 1.2; margin: 0 0 12px; letter-spacing: -0.4px; }
.article .meta { color: var(--muted); font-size: 0.92rem; margin-bottom: 28px; }
.article h2 { font-size: 1.45rem; margin: 42px 0 12px; padding-top: 8px; }
.article h3 { font-size: 1.15rem; margin: 30px 0 8px; color: var(--accent); }
.article p, .article li { color: #d3dbe8; }
.article ul, .article ol { padding-left: 24px; }
.article li { margin-bottom: 8px; }
.breadcrumb { font-size: 0.9rem; color: var(--muted); margin-bottom: 18px; }
.breadcrumb a { color: var(--muted); }

.callout {
  background: var(--surface-2); border-left: 4px solid var(--accent);
  border-radius: 0 var(--radius) var(--radius) 0; padding: 18px 22px; margin: 28px 0;
}
.callout.warn { border-left-color: var(--warn); }
.callout p { margin: 0; font-size: 0.98rem; }
.callout strong { color: var(--text); }

table.data { width: 100%; border-collapse: collapse; margin: 24px 0; font-size: 0.95rem; }
table.data th, table.data td { border: 1px solid var(--border); padding: 12px 14px; text-align: left; }
table.data th { background: var(--surface-2); color: var(--accent); font-weight: 700; }
table.data td { color: #d3dbe8; }
.table-wrap { overflow-x: auto; }

.toc {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px 24px; margin: 28px 0;
}
.toc h2 { font-size: 1.05rem !important; margin: 0 0 10px !important; }
.toc ol { margin: 0; padding-left: 22px; }
.toc li { margin-bottom: 6px; font-size: 0.97rem; }

.faq details {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px 22px; margin-bottom: 14px;
}
.faq summary { font-weight: 700; cursor: pointer; font-size: 1.05rem; }
.faq summary:hover { color: var(--accent); }
.faq details p { color: var(--muted); margin: 12px 0 0; }

/* ---------- Calculator ---------- */
.calc-wrap {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 34px; margin: 30px 0;
}
.calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; }
.field label { display: block; font-weight: 700; margin-bottom: 8px; font-size: 0.98rem; }
.field select, .field input {
  width: 100%; padding: 13px 14px; border-radius: 10px; font-size: 1rem;
  background: var(--bg-soft); color: var(--text); border: 1px solid var(--border);
}
.field select:focus, .field input:focus { outline: 2px solid var(--accent); border-color: var(--accent); }
.field .hint { font-size: 0.85rem; color: var(--muted); margin-top: 6px; }
.calc-result {
  margin-top: 26px; padding: 26px; border-radius: var(--radius);
  background: linear-gradient(135deg, rgba(34,211,238,0.10), rgba(167,139,250,0.10));
  border: 1px solid var(--accent); text-align: center;
}
.calc-result .range { font-size: clamp(1.6rem, 4vw, 2.4rem); font-weight: 800; margin: 8px 0; }
.calc-result .range .grad {
  background: linear-gradient(120deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.calc-result .detail { color: var(--muted); font-size: 0.95rem; }
.calc-error { color: #f87171; font-weight: 600; margin-top: 14px; text-align: center; }

/* ---------- Ads ---------- */
.ad-wrap { margin: 34px auto; max-width: 100%; text-align: center; }
.ad-label { font-size: 0.7rem; letter-spacing: 1.5px; text-transform: uppercase; color: #5b6b8c; margin-bottom: 6px; }

/* ---------- Footer ---------- */
.site-footer { border-top: 1px solid var(--border); background: var(--bg-soft); margin-top: 40px; }
.footer-inner {
  max-width: var(--maxw); margin: 0 auto; padding: 44px 22px 26px;
  display: grid; grid-template-columns: 1.4fr 1fr 1fr; gap: 30px;
}
.footer-inner h4 { margin: 0 0 12px; font-size: 1rem; color: var(--text); }
.footer-inner p, .footer-inner li { color: var(--muted); font-size: 0.93rem; }
.footer-inner ul { list-style: none; margin: 0; padding: 0; }
.footer-inner li { margin-bottom: 8px; }
.footer-inner a { color: var(--muted); }
.footer-inner a:hover { color: var(--accent); }
.footer-bottom {
  border-top: 1px solid var(--border); padding: 18px 22px; text-align: center;
  color: #5b6b8c; font-size: 0.85rem; max-width: var(--maxw); margin: 0 auto;
}

/* ---------- Misc ---------- */
.divider { border: 0; border-top: 1px solid var(--border); margin: 40px 0; }
.kbd-list { display: grid; gap: 16px; }
.gloss-term { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 20px 24px; }
.gloss-term h3 { margin: 0 0 8px; color: var(--accent); font-size: 1.1rem; }
.gloss-term p { margin: 0; color: #d3dbe8; font-size: 0.98rem; }
.contact-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 30px; margin: 24px 0;
}
.contact-card p { margin: 8px 0; }
.form-row { margin-bottom: 18px; }
.form-row label { display: block; font-weight: 700; margin-bottom: 8px; }
.form-row input, .form-row textarea {
  width: 100%; padding: 13px 14px; border-radius: 10px; font-size: 1rem;
  background: var(--bg-soft); color: var(--text); border: 1px solid var(--border);
  font-family: inherit;
}
.form-row textarea { min-height: 140px; resize: vertical; }

/* ---------- Responsive ---------- */
@media (max-width: 760px) {
  body { font-size: 16px; }
  .nav-links {
    display: none; flex-direction: column; align-items: flex-start; gap: 4px;
    position: absolute; top: 100%; left: 0; right: 0;
    background: var(--bg-soft); border-bottom: 1px solid var(--border); padding: 14px 22px;
  }
  .nav-links.open { display: flex; }
  .nav-links a { padding: 8px 0; }
  .nav-toggle { display: block; }
  .site-header { position: sticky; }
  .header-inner { position: relative; }
  .calc-grid { grid-template-columns: 1fr; }
  .calc-wrap { padding: 22px; }
  .footer-inner { grid-template-columns: 1fr; }
  .hero { padding: 56px 0 44px; }
}