html {
  box-sizing: border-box;
  background: #ffc600;
  font-family: "helvetica-neue";
  font-size: 20px;
  font-weight: 200;
}

body {
  margin: 0;
}

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

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

.panel {
  background: #6B0F9C;
  box-shadow: inset 0 0 0 5px rgba(255,255,255,0.1);
  color: white;
  text-align: center;
  align-items: center;
  /* Safari transitionend event.propertyName === flex */
  /* Chrome + FF transitionend event.propertyName === flex-grow */
  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://s4827.pcdn.co/wp-content/uploads/2016/09/Stars_1_iPad.jpg");
}
.panel2 {
  background-image: url("https://generations.fr/media/news/thumb/870x489_screenshot-www-33354.png");
}
.panel3 {
  background-image:url("https://images.unsplash.com/photo-1465188162913-8fb5709d6d57?ixlib=rb-0.3.5&q=80&fm=jpg&crop=faces&cs=tinysrgb&w=1500&h=1500&fit=crop&s=967e8a713a4e395260793fc8c802901d");
}
.panel4 {
  background-image:url("https://www.leadforensics.com/wp-content/uploads/2019/03/Motivation-e1566469475153.jpg");
}
.panel5 {
  background-image:url("https://images.wallpaperscraft.com/image/traffic_city_speed_131850_2560x1600.jpg");
}

/* Flex Items */
.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 { transform: translateY(0%); }
.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 {
  font-size: 40px;
  flex: 5;
}