Basic media query

style.css

/* mobile first */
h1 {
  color: #ff0000; /* red */
}

/* tablet */
@media only screen and (min-width: 768px) {
  h1 {
    color: #ffff00; /* yellow */
  }
  /* add more styles here for tablet */
}

/* desktop */
@media only screen and (min-width: 1000px) {
  h1 {
    color: #ff00ff; /* pink */
  }
  /* add more styles here for mobile */
}