/* =========================
   RESET / BASE
   ========================= */
* {
  box-sizing: border-box;
}

html, body {
  height: 100%;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  line-height: 1.55;
  color: var(--text);
  background:
    radial-gradient(1200px 600px at 20% -10%, rgba(77,163,255,.12), transparent),
    radial-gradient(1000px 500px at 120% 10%, rgba(190,163,255,.08), transparent),
    var(--bg);
}

a {
  color: inherit;
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

/* =========================
   THEME VARIABLES (DARK DEFAULT)
   ========================= */
:root {
  --bg: #0f1320;

  --surface: #12192b;
  --surface-2: #0e1526;

  --text: #e7ecf4;
  --muted: #a8b3c7;

  --brand: #4da3ff;
  --brand-strong: #2b84f0;

  --border: 1px solid rgba(255,255,255,0.08);
  --ring: rgba(77,163,255,0.45);

  --shadow: 0 6px 18px rgba(0,0,0,.25);
  --shadow-raise: 0 16px 30px rgba(0,0,0,.35);

  --radius: 16px;
  --radius-lg: 18px;
}

/* =========================
   LAYOUT HELPERS
   ========================= */
.container {
  width: min(1100px, 92vw);
  margin-inline: auto;
}

/* =========================
   NAVIGATION
   ========================= */
.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  position: sticky;
  top: 0;
  z-index: 10;

  background: linear-gradient(
    to bottom,
    rgba(15,19,32,0.9),
    rgba(15,19,32,0.55)
  );
  backdrop-filter: blur(10px);
  border-bottom: 1px solid rgba(255,255,255,0.06);
}

.nav .logo {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 10px;

  background: linear-gradient(160deg, var(--brand), var(--brand-strong));
  color: #081220;
  font-weight: 800;
  letter-spacing: .5px;
}

.nav ul {
  list-style: none;
  display: flex;
  gap: 16px;
  margin: 0;
  padding: 0;
}

.nav a {
  opacity: .9;
}

.nav a:hover {
  opacity: 1;
}

/* =========================
   THEME TOGGLE
   ========================= */
#themeToggle {
  display: inline-flex;
  align-items: center;
  gap: 6px;

  padding: 8px 12px;
  border-radius: 999px;

  background: var(--surface);
  border: var(--border);
  color: var(--text);

  font-weight: 700;
  cursor: pointer;
}

#themeToggle:hover {
  box-shadow: var(--shadow);
}

/* =========================
   HERO
   ========================= */
.hero {
  padding: 56px 24px 20px;
}

.hero-inner {
  max-width: 980px;
  margin: 0 auto;
  text-align: center;
}

.hero h1 {
  font-size: clamp(32px, 5vw, 56px);
  margin: 0 0 8px;
}

.tagline {
  color: var(--muted);
  font-size: clamp(16px, 2.5vw, 20px);
  margin-bottom: 14px;
}

.summary {
  max-width: 820px;
  margin: 0 auto 18px;
}

/* =========================
   CTA BUTTONS
   ========================= */
.cta {
  display: flex;
  justify-content: center;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 10px;
}

.btn {
  padding: 12px 16px;
  border-radius: 12px;
  font-weight: 700;

  background: var(--surface);
  border: var(--border);
  color: