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://source.unsplash.com/gYl-UtwNg_I/1500x1500); }
    .panel2 { background-image:url(https://source.unsplash.com/-KKLWDAgj2Q/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;
      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;
      /* it will take 5 times more than the rest of the pannels*/
      flex: 5;
    }