.blob {
  position: absolute;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, #6c7cff, transparent 70%);
  filter: blur(60px);
  animation: float 20s infinite alternate;
}

@keyframes float {
  from { transform: translate(0, 0); }
  to { transform: translate(200px, 100px); }
}