<!-- This example is the "Flex Panel Gallery" of the course #Javascript30. @author @wesbos -->
<div class="panels">
  <div class="panel panel1">
    <p>Hey</p>
    <p>Let's</p>
    <p>Dance</p>
  </div>
  <div class="panel panel2">
    <p>Give</p>
    <p>Take</p>
    <p>Receive</p>
  </div>
  <div class="panel panel3">
    <p>Experience</p>
    <p>It</p>
    <p>Today</p>
  </div>
  <div class="panel panel4">
    <p>Give</p>
    <p>All</p>
    <p>You can</p>
  </div>
  <div class="panel panel5">
    <p>Life</p>
    <p>In</p>
    <p>Motion</p>
  </div>
</div>

/* This example is the "Flex Panel Gallery" of the course #Javascript30. @author @wesbos */

html {
  box-sizing: border-box;
  background:#ffc600;
  font-size: 20px;
  font-weight: 200;
}
body {
  margin: 0;
}
*, *:before, *:after {
  box-sizing: inherit;
}

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

.panel {
  box-shadow:inset 0 0 0 5px rgba(255,255,255,0.1);
  color:white;
  /* 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);
  font-size: 20px;
  background-size:cover;
  background-position:center;
  flex:1;
  display: flex;
  flex-direction: column;
}

.panel.open {
  flex: 5;
  font-size:40px;
}


.panel1 { background-image:url(https://source.unsplash.com/gYl-UtwNg_I/1500x1500); }
.panel2 { background-image:url(https://source.unsplash.com/1CD3fd8kHnE/1500x1500); }
.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://source.unsplash.com/ITjiVXcwVng/1500x1500); }
.panel5 { background-image:url(https://source.unsplash.com/3MNzGlQM7qs/1500x1500); }

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

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

/* This example is the "Flex Panel Gallery" of the course #Javascript30. @author @wesbos */
const panels = document.querySelectorAll('.panel');
panels.forEach(panel => panel.addEventListener('click', () => {
  panel.classList.toggle('open');
}));
panels.forEach(panel => panel.addEventListener('transitionend', (e) =>  {
  e.propertyName.includes('flex') && panel.classList.toggle('open-active');
}));