.flex-container {
  width: 720px;
  margin: 0 auto;
}
html {
  font-size: 18px;
}
@media (max-width: 1600px) {
  html {
    font-size: 18px;
  }
  .flex-container {
    width: 720px;
  }
}
@media (max-width: 1200px) {
  html {
    font-size: 18px;
  }
  .flex-container {
    width: 640px;
  }
}
@media (max-width: 688px) {
  html {
    font-size: 16px;
  }
  .flex-container {
    display: block;
    width: calc(100% - 32px);
    padding-left: 16px;
    padding-right: 16px;
  }
}