:root {
  --pink:       #e6007e;
  --blue:       #009fe3;
  --teal:       #27cfc3;
  --grad:       linear-gradient(135deg, #e6007e 0%, #009fe3 100%);
  --dark:       #0d0d0d;
  --dark-600:   #1a1a1a;
  --dark-400:   #2e2e2e;
  --grey-500:   #676767;
  --grey-400:   #888888;
  --grey-100:   #e0e0e0;
  --white:      #ffffff;

  --font-display: 'Bebas Neue', 'Arial Black', sans-serif;
  --font-heading: 'Poppins', system-ui, sans-serif;
  --font-body:    'Poppins', system-ui, sans-serif;

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

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  background: var(--dark);
  color: var(--grey-100);
  font-family: var(--font-body);
  font-size: 17px;
  line-height: 1.6;
  overflow-x: hidden;
  min-height: 300vh;
}

/* ═══════════════════════════════════════════════════════════
   DEMO CONTENT (not part of the module)
   ═══════════════════════════════════════════════════════════ */

.demo-section {
  max-width: 720px;
  margin: 0 auto;
  padding: clamp(48px, 10vw, 120px) 24px;
}

.demo-section h2 {
  font-family: var(--font-heading);
  font-weight: 600;
  font-size: clamp(1.6rem, 3vw, 2.2rem);
  color: var(--white);
  margin-bottom: 16px;
  background: var(--grad);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.demo-section p {
  color: var(--grey-400);
  font-size: 15px;
  line-height: 1.75;
  margin-bottom: 14px;
}

.demo-section .badge {
  display: inline-block;
  padding: 4px 14px;
  border-radius: 20px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  background: var(--dark-400);
  color: var(--grey-400);
  margin-bottom: 20px;
}

.demo-divider {
  max-width: 720px;
  margin: 0 auto;
  border: none;
  border-top: 1px solid var(--dark-400);
}

/* ═══════════════════════════════════════════════════════════
   MODULE 18 — SCROLL TO TOP
   ═══════════════════════════════════════════════════════════ */

.scroll-top-btn {
  position: fixed;
  bottom: 32px;
  right: 32px;
  z-index: 9990;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  border: none;
  background: var(--grad);
  box-shadow: 0 4px 24px rgba(230, 0, 126, 0.3);
  cursor: pointer;
  display: grid;
  place-items: center;

  opacity: 0;
  pointer-events: none;
  transform: translateY(12px);
  transition:
    opacity 0.3s ease,
    transform 0.3s var(--ease-out),
    box-shadow 0.25s ease,
    scale 0.2s var(--ease-out);
}

.scroll-top-btn.is-visible {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
}

.scroll-top-btn:hover {
  scale: 1.1;
  rotate: -10deg;
  box-shadow: 0 8px 32px rgba(0,159,227,0.35), 0 0 20px rgba(0,159,227,0.25);
  outline: 2px solid rgba(0,159,227,0.8);
  outline-offset: 3px;
}

.scroll-top-btn:active {
  scale: 0.95;
  rotate: 0deg;
}

.scroll-top-btn:focus-visible {
  outline: 2px solid var(--teal);
  outline-offset: 3px;
}

.scroll-top-btn svg {
  width: 20px;
  height: 20px;
  stroke: var(--white);
  stroke-width: 2;
  fill: none;
  stroke-linecap: round;
  stroke-linejoin: round;
}