JSFiddle - React, Tailwind, and code Playground

HTML

<nav class="nav-service">
  <a href="" class="nav-item">Link 1</a>
  <a href="" class="nav-item">Link 2</a>
</nav>

CSS

.nav-service a {
  font-size: 10px; /* surchargé par la media query */
}

.nav-service .nav-item {
  color: red; /* non surchargé par la media query */
}

@media screen and (min-width: 768px) {
  .nav-service a {
    font-size: 20px;
    margin-right: 40px;
    color: green;
  }
}