/* ============================================================
   Zero to One Academy — Design System
   Apple/Linear-precise · matte dark cinematic · glass depth
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=Geist:wght@300;400;500;600;700;800;900&family=Geist+Mono:wght@400;500;600&display=swap');

:root {
  /* --- Surfaces (cool dark navy-charcoal) --- */
  --bg-0: oklch(0.145 0.018 264);     /* deepest */
  --bg-1: oklch(0.175 0.020 264);     /* base */
  --bg-2: oklch(0.205 0.022 264);     /* raised */
  --bg-light: oklch(0.965 0.004 264); /* readability sections */
  --bg-light-2: oklch(0.99 0.003 264);

  /* --- Text --- */
  --ink: oklch(0.97 0.005 264);
  --ink-soft: oklch(0.80 0.012 264);
  --ink-mute: oklch(0.635 0.016 264);
  --ink-faint: oklch(0.50 0.018 264);
  --ink-on-light: oklch(0.22 0.02 264);
  --ink-on-light-mute: oklch(0.46 0.02 264);

  /* --- Accents (electric blue → indigo) --- */
  --blue: oklch(0.64 0.20 258);
  --blue-bright: oklch(0.70 0.19 252);
  --indigo: oklch(0.62 0.20 285);
  --accent-grad: linear-gradient(120deg, var(--blue-bright), var(--indigo));
  --accent-grad-soft: linear-gradient(120deg, oklch(0.70 0.19 252 / 0.16), oklch(0.62 0.20 285 / 0.16));

  /* --- Glass --- */
  --glass-fill: oklch(0.99 0.01 264 / 0.045);
  --glass-fill-2: oklch(0.99 0.01 264 / 0.07);
  --glass-stroke: oklch(0.99 0.01 264 / 0.10);
  --glass-stroke-2: oklch(0.99 0.01 264 / 0.16);

  /* --- Hairlines --- */
  --line: oklch(0.99 0.01 264 / 0.08);
  --line-strong: oklch(0.99 0.01 264 / 0.14);

  /* --- Type --- */
  --sans: 'Geist', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --mono: 'Geist Mono', ui-monospace, 'SF Mono', monospace;

  /* --- Geometry --- */
  --r-sm: 12px;
  --r-md: 18px;
  --r-lg: 26px;
  --r-xl: 36px;
  --maxw: 1200px;
  --gutter: clamp(20px, 5vw, 64px);

  /* --- Shadow --- */
  --shadow-card: 0 1px 0 oklch(1 0 0 / 0.04) inset, 0 24px 60px -28px oklch(0.10 0.03 264 / 0.9);
  --shadow-float: 0 40px 100px -40px oklch(0.05 0.05 270 / 0.85), 0 1px 0 oklch(1 0 0 / 0.06) inset;
  --glow-blue: 0 0 0 1px oklch(0.70 0.19 252 / 0.35), 0 16px 60px -16px oklch(0.64 0.20 258 / 0.6);

  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; overflow-x: clip; }

body {
  font-family: var(--sans);
  background: var(--bg-1);
  color: var(--ink);
  line-height: 1.5;
  letter-spacing: -0.011em;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

::selection { background: oklch(0.70 0.19 252 / 0.32); color: var(--ink); }

a { color: inherit; text-decoration: none; }
button { font-family: inherit; cursor: pointer; border: none; background: none; color: inherit; }
img, svg { display: block; max-width: 100%; }

/* ---------- Layout helpers ---------- */
.wrap { max-width: var(--maxw); margin: 0 auto; padding-inline: var(--gutter); }
.section { position: relative; padding-block: clamp(80px, 12vh, 160px); }

.eyebrow {
  font-family: var(--mono);
  font-size: 12.5px;
  font-weight: 500;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--blue-bright);
  display: inline-flex;
  align-items: center;
  gap: 10px;
}
.eyebrow::before {
  content: "";
  width: 22px; height: 1px;
  background: linear-gradient(90deg, var(--blue-bright), transparent);
}

.h-display {
  font-weight: 600;
  letter-spacing: -0.035em;
  line-height: 1.02;
  font-size: clamp(40px, 6.6vw, 92px);
}
.h-section {
  font-weight: 600;
  letter-spacing: -0.03em;
  line-height: 1.05;
  font-size: clamp(32px, 4.6vw, 60px);
}
.lede {
  font-size: clamp(17px, 1.55vw, 21px);
  color: var(--ink-soft);
  line-height: 1.55;
  font-weight: 400;
  max-width: 60ch;
}

.grad-text {
  background: linear-gradient(110deg, var(--blue-bright) 10%, var(--indigo) 90%);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 9px;
  height: 50px;
  padding-inline: 26px;
  border-radius: 999px;
  font-size: 15px;
  font-weight: 500;
  letter-spacing: -0.01em;
  white-space: nowrap;
  transition: transform .4s var(--ease), box-shadow .4s var(--ease), background .3s, border-color .3s, color .3s;
  will-change: transform;
}
.btn:active { transform: scale(0.97); }
.btn svg { width: 17px; height: 17px; }

.btn-primary {
  background: var(--accent-grad);
  color: oklch(0.99 0.01 264);
  box-shadow: 0 10px 30px -10px oklch(0.64 0.20 258 / 0.7), 0 1px 0 oklch(1 0 0 / 0.25) inset;
}
.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 18px 44px -12px oklch(0.64 0.20 258 / 0.85), 0 1px 0 oklch(1 0 0 / 0.3) inset;
}

.btn-ghost {
  background: var(--glass-fill-2);
  color: var(--ink);
  border: 1px solid var(--glass-stroke-2);
  backdrop-filter: blur(12px);
}
.btn-ghost:hover {
  background: oklch(0.99 0.01 264 / 0.12);
  border-color: var(--glass-stroke-2);
  transform: translateY(-2px);
}

.btn-light { background: var(--ink); color: var(--bg-0); }
.btn-light:hover { transform: translateY(-2px); box-shadow: 0 14px 30px -14px oklch(0 0 0 / 0.5); }

.btn-text {
  height: auto; padding: 0; border-radius: 0;
  color: var(--ink-soft);
  display: inline-flex; align-items: center; gap: 7px;
}
.btn-text:hover { color: var(--ink); }
.btn-text .arrow { transition: transform .3s var(--ease); }
.btn-text:hover .arrow { transform: translateX(4px); }

/* ---------- Glass card ---------- */
.glass {
  background: var(--glass-fill);
  border: 1px solid var(--glass-stroke);
  border-radius: var(--r-lg);
  backdrop-filter: blur(20px) saturate(1.2);
  -webkit-backdrop-filter: blur(20px) saturate(1.2);
}

/* ---------- Background atmosphere ---------- */
.bg-atmos {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background:
    radial-gradient(120% 80% at 50% -10%, oklch(0.30 0.07 264 / 0.55), transparent 60%),
    radial-gradient(90% 60% at 85% 8%, oklch(0.45 0.16 285 / 0.16), transparent 55%),
    radial-gradient(80% 60% at 8% 20%, oklch(0.45 0.18 252 / 0.14), transparent 55%);
}
.bg-grid {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background-image:
    linear-gradient(oklch(0.99 0.01 264 / 0.022) 1px, transparent 1px),
    linear-gradient(90deg, oklch(0.99 0.01 264 / 0.022) 1px, transparent 1px);
  background-size: 64px 64px;
  mask-image: radial-gradient(110% 90% at 50% 0%, #000 30%, transparent 75%);
  -webkit-mask-image: radial-gradient(110% 90% at 50% 0%, #000 30%, transparent 75%);
}

/* ---------- Reveal animation (progressive enhancement) ---------- */
.reveal {
  transition: opacity .9s var(--ease-out), transform .9s var(--ease-out);
  transition-delay: var(--d, 0ms);
}
html.js .reveal { opacity: 0; transform: translateY(26px); }
html.js .reveal.in { opacity: 1; transform: none; }

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; }
  .reveal { opacity: 1; transform: none; transition: none; }
  html { scroll-behavior: auto; }
}