body {
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  background-color: #2c3e50;
}

.cradle {
  display: flex;
  border-top: 10px solid white;
}

.cradle span {
  display: block;
  width: 3px;
  height: 300px;
  background-color: white;
  margin: 0 29px;
  position: relative;
  transform-origin: top;
}

.cradle span:before {
  content: "";
  position: absolute;
  bottom: 0;
  left: 0;
  width: 60px;
  height: 60px;
  border-radius: 50%;
  background-color: white;
  transform: translateX(-50%);
}

.cradle span:first-child {
  animation: left-arm 2s ease-in infinite;
}

.cradle span:last-child {
  animation: right-arm 2s ease-in infinite 1s;
}

@keyframes left-arm {
  0% {
    transform: rotate(0deg);
  }
  25% {
    transform: rotate(60deg);
  }
  50% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(0deg);
  }
}

@keyframes right-arm {
  0% {
    transform: rotate(0deg);
  }
  25% {
    transform: rotate(-60deg);
  }
  50% {
    transform: rotate(0deg);
  }
  100% {
    transform: rotate(0deg);
  }
}