box-shadow in Superhuman

Before

.card {
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
}

After

.card {
  border: 1px solid #e0e0e0;
  /* box-shadow as progressive enhancement */
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
}