@media screen and (max-width: 900px) {
  .upper-intro {
    padding: 50px;
  }
  .upper-intro p {
    width: 80%;
  }
  #countdownSection {
    width: 70%; 
    left: 15%;
  }
  .nophone {
    display: none;
  }
  .yesphone {
    display: inline;
  }
}

@media screen and (max-width: 650px) {
  body footer p {
    display: none;
  }
}

@media screen and (max-width: 500px) {
  .upper-intro {
    padding: 25px;
  }
  .upper-intro p {
    width: 100%;
  }
  #countdownSection {
    width: 80%; 
    left: 10%;
  }
}

@media screen and (max-width: 350px) {
  #countdownSection #countdown {
    font-size: smaller;
  }
  body header nav a {
    width: 60%;
  }
  body header nav a :last-child {
    width: 100%;
  }
}