html {
  box-sizing: border-box;
  font-family: 'Helvetica Neue', sans-serif; 
  font-weight: 200;
}

body {
  margin: 0;
}

* {
  box-sizing: inherit;
}

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

.panel:hover {
  cursor: pointer;
  filter: grayscale(75%);
}

.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 0.2s cubic-bezier(0.61,-0.19, 0.7,-0.11),
    flex 0.2s cubic-bezier(0.61,-0.19, 0.7,-0.11),
    background 0.1s;
  font-size: 20px;
  background-size: cover;
  background-position: center;
  flex: 1;
  justify-content: center;
  display: flex;
  flex-direction: column;
}

.panel1 { background-image:url(https://images.unsplash.com/photo-1465513670158-c3ac6c8d1a87); }
.panel2 { background-image:url(https://images.unsplash.com/photo-1512191395-990953d46dde); }
.panel3 { background-image:url(https://images.unsplash.com/photo-1497106636505-e4fd6e16d74c); }
.panel4 { background-image:url(https://images.unsplash.com/photo-1454357110064-3d600740d47a); }
.panel5 { background-image:url(https://images.unsplash.com/photo-1511339670939-46caa79b6e6e); }

/* Flex Items/Children */
.panel > * {
  margin: 0;
  width: 100%;
  transition: transform 0.1s;
  flex: 1 0 auto;
  display: flex;
  justify-content: center;
  align-items: center;
}

/* offscreen */
.panel > *:first-child { transform: translateY(-100%); } 
.panel.open-active > *:first-child { transform: translateY(0); }
/* onscreen */
.panel > *:last-child { transform: translateY(100%); } 
.panel.open-active > *:last-child { transform: translateY(0); }

.panel p {
  text-transform: uppercase;
  font-family: 'Amatic SC', cursive;
  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: 5;
  font-size: 40px;
}