html, body {
  background-color: #000000;
}
@keyframes float-sm { 0%,100% { transform: translateY(0); } 50% { transform: translateY(-9px); } }
@keyframes float-md { 0%,100% { transform: translateY(0); } 50% { transform: translateY(-5px); } }
@keyframes float-lg { 0%,100% { transform: translateY(0); } 50% { transform: translateY(-7px); } }

.card-1 img { animation: float-sm 6s ease-in-out infinite; }
.card-2 img { animation: float-md 4s ease-in-out infinite 0.5s; }
.card-3 img { animation: float-lg 8s ease-in-out infinite 1s; }