.container {
  display: flex;
  width: 100%;
  padding: 4% 2%;
  box-sizing: border-box;
 height: 100%;
}

.box {
  flex: 1;
  overflow: hidden;
  transition: 0.5s;
  margin: 0 2%;
  box-shadow: 0 20px 30px rgba(0, 0, 0, 0.1);
  line-height: 0;
}

.box > img {
  width: 200%;
  height: calc(100% - 10vh);
  -o-object-fit: cover;
     object-fit: cover;
  transition: 0.5s;
}

.box > span {
  font-size: 3.8vh;
  display: block;
  text-align: center;
  height: 10vh;
  line-height: 2.6;
}

.box:hover {
  flex: 1 1 50%;
}

.box:hover > img {
  width: 100%;
  height: 100%;
}

/* ensure full-height centering inside iframe */
html, body { height: 100%; }
body {
  background: transparent;
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  transform: scale(0.8);    /* 0.8 = 80% of original size */
  transform-origin: center; /* adjust where it scales from */
}

.container { min-height: 0; }