/****************************
-- Positioning --
****************************/
img {
  display: block;
  max-width: 100%;
}

.img-wrap {
  display: block;
  height: 0;
  position: relative;
  width: 100%;
}

.img-wrap.w4h3 {
  padding-bottom: 75%; /* 300/400 */
}

.img-wrap.w28h19 {
  padding-bottom: 67.8572%; /* 200/300 */
}

.img-wrap.w3h2 {
  padding-bottom: 66.66%; /* 200/300 */
}

.img-wrap.w2h1 {
  padding-bottom: 50%; /* 100/200 */
}

.img-wrap.w1h1 {
  padding-bottom: 100%; /* 100/200 */
}

.img-wrap img {
  bottom: 0;
  left: 0;
  margin: auto;
  max-height: 100%;
  max-width: 100%;
  position: absolute;
  right: 0;
  top: 0;
}