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;
    /* 가로로 배열 */
    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;
    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;
    /* 공간을 준다 */
    flex: 1;
    /* 위에 모여있던걸 가운데 정렬 하고 가로로 쭉펴줌  */
    justify-content: center;
    align-items: center;
    display: flex;
    /* 세로로 변경 */
    flex-direction: column;
}

.panel1 { background-image:url(https://source.unsplash.com/gYl-UtwNg_I/1500x1500); }
.panel2 { background-image:url(https://source.unsplash.com/rFKUFzjPYiQ/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;
    /* 경계 보여주기
    border: 1px solid red; */
    /* 위아래로 펼치기 */
    flex: 1 0 auto;
    display: flex;
    /* 가운데정렬 */
    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 {
    flex:5;
    font-size: 40px;
}