/* BackcomHub — base stylesheet */
:root {
  --brand:        #2563eb;
  --brand-dark:   #1d4ed8;
  --text:         #14181f;
  --text-muted:   #5b6675;
  --bg:           #ffffff;
  --bg-soft:      #f6f8fa;
  --border:       #e3e8ee;
  --radius:       12px;
  --maxw:         1120px;
  --font:         system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --text:       #e8ecf1;
    --text-muted: #9aa7b6;
    --bg:         #0f1319;
    --bg-soft:    #161b23;
    --border:     #262d38;
  }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.65;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

img { max-width: 100%; height: auto; display: block; }

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

.container { width: 100%; max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }

/* ── Header ─────────────────────────────────────────────────────────────── */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.site-header .container {
  display: flex; align-items: center; justify-content: space-between;
  height: 64px; gap: 24px;
}
.logo { display: flex; align-items: center; gap: 10px; font-weight: 700; font-size: 18px; color: var(--text); }
.logo:hover { text-decoration: none; }
.logo img { width: 28px; height: 28px; }

.nav { display: flex; gap: 24px; }
.nav a { color: var(--text-muted); font-size: 15px; font-weight: 500; }
.nav a:hover { color: var(--brand); text-decoration: none; }

/* ── Hero ───────────────────────────────────────────────────────────────── */
.hero { padding: 80px 0 64px; text-align: center; background: var(--bg-soft); border-bottom: 1px solid var(--border); }
.hero h1 { margin: 0 0 16px; font-size: clamp(30px, 5vw, 46px); line-height: 1.15; letter-spacing: -0.02em; }
.hero p { margin: 0 auto 32px; max-width: 620px; font-size: 18px; color: var(--text-muted); }

.btn {
  display: inline-block; padding: 12px 26px; border-radius: var(--radius);
  background: var(--brand); color: #fff; font-weight: 600; font-size: 15px;
  border: 1px solid var(--brand); transition: background .15s ease;
}
.btn:hover { background: var(--brand-dark); border-color: var(--brand-dark); text-decoration: none; }
.btn-ghost { background: transparent; color: var(--text); border-color: var(--border); }
.btn-ghost:hover { background: var(--bg-soft); border-color: var(--border); }

/* ── Sections & cards ───────────────────────────────────────────────────── */
section, section.container { padding-top: 64px; padding-bottom: 64px; }
section h2 { margin: 0 0 8px; font-size: 28px; letter-spacing: -0.01em; }
section .sub { margin: 0 0 36px; color: var(--text-muted); }

.grid { display: grid; gap: 20px; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); }

.card {
  padding: 24px; border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--bg); transition: border-color .15s ease, transform .15s ease;
}
.card:hover { border-color: var(--brand); transform: translateY(-2px); }
.card h3 { margin: 0 0 8px; font-size: 17px; }
.card p  { margin: 0; color: var(--text-muted); font-size: 15px; }

/* ── Footer ─────────────────────────────────────────────────────────────── */
.site-footer { padding: 40px 0; border-top: 1px solid var(--border); background: var(--bg-soft); }
.site-footer .container { display: flex; flex-wrap: wrap; gap: 16px; justify-content: space-between; align-items: center; }
.site-footer p { margin: 0; color: var(--text-muted); font-size: 14px; }
.site-footer .nav a { font-size: 14px; }

@media (max-width: 640px) {
  .nav { display: none; }
  .hero { padding: 56px 0 44px; }
  section, section.container { padding-top: 48px; padding-bottom: 48px; }
}