.row, .column, .demo {
  width: 40%;
  margin-left: auto;
  margin-right: auto;
}

  @media (max-width: 280px) {
    .mySlides {
      max-width: 260px;
    }
  }
  
  @media (max-width: 280px) {
      .mySlides img {
        max-width: 220px;
      }
    }

@media (min-width: 290px) and (max-width: 414px) {
  .mySlides {
    max-width: 270px;
  }
}
@media (min-width: 290px) and (max-width: 414px) {
    .mySlides img {
      max-width: 250px;
    }
  }

  @media (min-width: 420px) and (max-width: 540px) {
    .mySlides {
      max-width: 400px;
    }
  }
  @media (min-width: 420px) and (max-width: 540px) {
    .mySlides img {
      max-width: 360px;
    }
  }
  @media (min-width: 550px) and (max-width: 720px) {
    .mySlides {
      max-width: 520px;
    }
  }
  @media (min-width: 550px) and (max-width: 720px) {
    .mySlides img {
      max-width: 500px;
    }
  }