.a,
.b {
  width: 20px;
  @media screen and ( max-width: 900px) {
    @keyframes identifier {
      0% {
        top: 0;
        left: 0;
      }
      30% {
        top: 50px;
      }
      68%,
      72% {
        left: 50px;
      }
      100% {
        top: 100px;
        left: 100%;
      }
    }
  }
}

.xyz{
  @keyframes popanit {
    0% {
      top: 0;
      left: 0;
    }
    30% {
      top: 50px;
    }
    68%,
    72% {
      left: 50px;
    }
    100% {
      top: 100px;
      left: 100%;
    }
  }
}