ul {
  margin: 100px auto 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  text-align: center;
  padding: 0;     
  min-width: 200px;
  margin: 20px;
  padding: 0 40px;
  background-color: #e9f3ff;
  border-radius:5px;
  font-weight:600;
}

@media screen and (min-width: 400px) {
    ul {
      flex-direction: row;
      min-width: 600px;
    }
}

ul a {
  display: inline-block;
  text-decoration: none;
  color: #001e42;
  font-size: 13px;
  letter-spacing: 1px;
  position: relative;
  transition: all 0.4s ease;
  padding: 30px;
}

ul a::after { 
  content: "";
  position: absolute;
  height: 2px;
  background-color: #4d94c4;
  width: 0;
  left: 50%;
  bottom: 0;
  transform: translateX(-50%);
  transition: 0.5s cubic-bezier(0.68, -0.55, 0.265, 1.55) all;
}

ul a:hover { color: #4d94c4; }
ul a:hover::after { width: 100%; }