body {
  margin: 0;
  background: #fff;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

.box {
  width: 200px;
  height: 200px;
  background: #3a84f5;
  border-radius: 10%;
  box-shadow: 10px 10px 10px rgba(0,0,0,0.25);
  animation: float 3s ease-in-out infinite;
}

@keyframes float {
  0%, 100% { transform: translateY(-60px); }
  50% { transform: translateY(60px); }
}