flexbox08

@media (min-width: 40rem) {
  .plan__list { 
    width: 100%;
    text-align: center;
    display: flex;
    margin:auto;
    justify-content: center;
    align-items: center;
  }

  .plan {
    display: flex;
    flex-direction: column;
    width: 30%;
    vertical-align: middle;
    min-width: 13rem;
    max-width: 25rem;
    height: 30rem;
  }

  .plan--highlighted {
    z-index: 1000;
    height: 35rem;
    box-shadow: 2px 2px 2px 2px rgba(0, 0, 0, 0.5);
  }
}

@media (min-width: 40rem) {
  /*assignment*/
  .key-feature {
    display: flex;
    width: 30%;
    max-width: 25rem;
    vertical-align: top;
    flex-direction: column;
  }

  .key-feature__list {
    display: flex;
    flex-direction: row;
    justify-content: center;
  }

  /*assignment => add .key-feature_list => flex container*/
}