.base-class {
    -webkit-transition:all cubic-bezier(0.250, 0.460, 0.450, 0.940) 0.5s;
    transition:all cubic-bezier(0.250, 0.460, 0.450, 0.940) 0.5s;
  }

  .base-class.my-class {
    color: red;
    font-size:3em;
  }