body {
  background: linear-gradient(to bottom, #001f3f, #0074D9);
  color: white;
  font-family: 'Segoe UI', sans-serif;
}

.tree {
  width: 100px;
  height: 150px;
  background-color: green;
  animation: dance 2s infinite ease-in-out;
}

@keyframes dance {
  0% { transform: rotate(0deg); }
  50% { transform: rotate(10deg); }
  100% { transform: rotate(-10deg); }
}