style.css

@import url('https://fonts.googleapis.com/css?family=Muli&display=swap');

* {
    box-sizing: border-box;
}

body {
    font-family: 'Muli', sans-serif;
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100vh;
    overflow: hidden;
    margin: 0;
 }

 .container {
     display: flex;
     width: 90vw;
 }

  .panel {
     background-size: cover;
     background-position: center;
     background-repeat: no-repeat;
     height: 80vh;
     border-radius: 50px;
    color: #fff;
    cursor: pointer;
    flex: 0.5;
    margin: 10px;
    position: relative;
    transition: flex 0.7s ease-in;
 }

.panel h3 {
     font-size: 24px;
     position: absolute;
     bottom: 20px;
     left: 20px;
     margin: 0;
     opacity: 0;
 } 

.panel.active {
     flex: 5;
 }

 .panel.active h3 {
     opacity: 1;
     transition: opacity 0.3s ease-in 0.4s;
 }


 @media(max-width: 480px) {
     .container {
         width: 100vw;
     }

     .panel:nth-of-type(4),
     .panel:nth-of-type(5) {
         display: none;
     }
 }