html {
  box-sizing: border-box;
  background: pink;
}

body {
  margin: 0;
}

*,
*::after,
*::before {
  box-sizing: inherit;
}

.panels {
  overflow: hidden;
  display: flex;
  min-height: 100vh;
}

.panel {
  box-shadow: inset 0 0 0 5px rgba(255, 255, 255, 0.1);
  color: white;
  text-align: center;
  align-items: center;
  transition: font-size 0.7s cubic-bezier(0.61, -0.19, 0.7, -0.11),
    flex 0.7s cubic-bezier(0.61, -0.19, 0.7, -0.11), background 0.2s;
  font-size: 20px;
  background-size: cover;
  background-position: center;
  flex: 1;
  justify-content: center;
  align-items: center;
  display: flex;
  flex-direction: column;
}

.panel1 {
  background-image: url("https://lh3.googleusercontent.com/proxy/WDovHGdDW3etV90BLInltEJy_bqlTFBZ4q4I6Acty28NOKcVUa871rKtUXDQQlCEFXOfyyrSQZsve-vqJQQMWNudV_CCHZVajLGjM-N3LssY1onvREpzvHdTQLn5");
}

.panel2 {
  background-image: url("http://www.evolo.us/wp-content/uploads/2019/04/0516-0.jpg");
}

.panel3 {
  background-image: url("https://64.media.tumblr.com/66efd91bf13521db745622dc3f32db4f/tumblr_mhced3yDnQ1rga5m1o1_500.jpg");
}

.panel4 {
  background-image: url("https://previews.123rf.com/images/thesupe87/thesupe871105/thesupe87110500039/9591782-vertical-aerial-view-of-the-manhattan-section-of-new-york-city-including-all-of-the-buildings-and-sk.jpg");
}

.panel > * {
  margin: 0;
  width: 100%;
  transition: transform 0.5s;
  flex: 1 0 auto;
  display: flex;
  justify-content: center;
  align-items: center;
}

.panel > *:first-child {
  transform: translateY(-100%);
}

.panel.open-active > *:first-child,
.panel.open-active > *:last-child {
  transform: translateY(0);
}

.panel > *:last-child {
  transform: translateY(100%);
}

.panel p {
  text-transform: uppercase;
  text-shadow: 0 0 4px rgba(0, 0, 0, 0.72), 0 0 14px rgba(0, 0, 0, 0.45);
  font-size: 2em;
}

.panel p:nth-child(2) {
  font-size: 4em;
}

.panel.open {
  flex: 4;
}