div {
  width: 100%;
  height: 100vh;
  background: #111;
}
div::before{
  content: '╲╱';
  color: #fff;
  position: absolute;
  opacity: 0.7;
  text-shadow: 0 0 6px rgba(0,0,0,0.5);
  font-size: 20px;
  width: 60px;
  height: 40px;
  line-height: 40px;
  text-align: center;
  border-radius: 10px;
  bottom: 20px;
  left: 50%;
  margin-left: -30px;
  animation: bounce 1s ease infinite;
}

@keyframes bounce {
  50% {
    transform: translateY(-50%);
  }
  100% {
    transform: translateY(0);
  }
}