:root {
  --brand: #004b7a;
  --ink: #1f2a37;
  --muted: #6b7280;
  --paper: #f9fafb;
  --accent: #0ea5e9;
}

body {
  font-family: Montserrat, system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  color: var(--ink);
  background: var(--paper);
}

a {
  color: var(--accent);
}

a:hover {
  color: #0b6ba6;
}

.back-to-top {
  position: fixed;
  right: 28px;
  bottom: 28px;

  width: 48px;
  height: 48px;

  display: flex;
  align-items: center;
  justify-content: center;

  border-radius: 50%; /* round button */
  background: rgba(7, 69, 135, 0.95);
  color: #ffffff;

  font-size: 20px;
  font-weight: 700;
  text-decoration: none;

  box-shadow: 0 8px 22px rgba(0, 0, 0, 0.25);

  /* always visible */
  opacity: 1;
  pointer-events: auto;

  transition:
    transform 0.2s ease,
    box-shadow 0.2s ease,
    background 0.2s ease;
}

.back-to-top:hover {
  transform: translateY(-3px);
  box-shadow: 0 12px 28px rgba(0, 0, 0, 0.32);
  background: rgba(7, 69, 135, 1);
}

.back-to-top:active {
  transform: translateY(0);
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.22);
}

@media (max-width: 640px) {
  .back-to-top {
    right: 16px;
    bottom: 16px;
    width: 42px;
    height: 42px;
    font-size: 18px;
  }
}