body {
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  font-family: sans-serif;
}

ul {
  margin: 0;
  padding: 0;
  display: flex;
  list-style: none;
}

ul li a{
    color: #272727;
    font-size: 20px;
    text-decoration: none;
    text-transform: uppercase;
    padding: 5px 10px;
    margin: 0px 10px;
    position: relative;
    transition: all .5s ease-in-out;
}

a:hover{
    background-color: #e91e63;
    color: white;
}

a::before{
    content: "";
    position: absolute;
    bottom: 12px;
    left: 12px;
    width: 12px;
    height: 12px;
    border: 3px solid #e91e63;
    border-width: 0 0 3px 3px;
    opacity: 0;
    transition: all .3s ease-in-out;
}

ul li a:hover::before{
    opacity: 1;
    bottom: -8px;
    left: -8px;
}

a::after{
    content: "";
    position: absolute;
    right: 12px;
    top: 12px;
    width: 12px;
    height: 12px;
    border: 3px solid #e91e63;
    border-width: 3px 3px 0 0;
    opacity: 0;
    transition: all .3s ease-in-out;
}

ul li a:hover::after{
    opacity: 1;
    top: -8px;
    right: -8px;
}