.about-us {
  background-color: rgba(90, 4, 4, .9);
  /* color: #253029; */
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 2rem 2rem 4rem;
  position: relative;
}

.introduction, .motto {
  max-width: 900px;
  margin-left: auto;
  margin-right: auto;
}

.introduction {
  text-align: center;
  font-size: 14px;
}

.motto {
  display: grid;
  margin: 1rem auto .5rem;
  padding: .5rem;
  grid-template-columns: repeat(4, 1fr);
  column-gap: .5rem;
  row-gap: .5rem;
  justify-content: center;
}
.criteria{
  display: flex;
  flex-direction: column;
  height: 250px;
  padding: 1rem;
  font-size: .75rem;;
}

.criteria img {
  width: 100%;
  height: 50%;
  background: transparent;
}

.criteria h3 {
  margin: 1rem 0 0;
  font-size: 1rem;
  color: silver;
  font-family: serif;
  letter-spacing: 1px;
}
.criteria p {
  color: #dad8d8;
}

.wave {
  position: absolute;
  bottom: 0;
  left: 0;
  z-index: -1;
  width: 100%;
  overflow: hidden;
  line-height: 0;
}
@media only screen and (max-width: 950px) {
  .about-us {
    padding: 1rem 1rem;
  }
  .motto {
    grid-template-columns: repeat(2, 1fr);
    margin: .5rem auto;
  }
}
@media only screen and (max-width: 550px) {
  .motto {
    grid-template-columns: 1fr;
    max-width: 80%;
  }
  .criteria {
    justify-self: stretch;
    align-items: center; 
    justify-content: center;
    text-align: center;
  }
  .criteria img {
    width: 85%
  }
}