style.css

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

* {
  -webkit-box-sizing: border-box;
          box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: 'Roboto', sans-serif;
  height: 100vh;
}

.container {
  position: relative;
  overflow: hidden;
  width: 100vw;
  height: 100vh;
}

.sidebar {
  height: 100%;
  width: 35%;
  position: absolute;
  top: 0;
  left: 0;
  -webkit-transition: -webkit-transform 0.5s ease-in-out;
  transition: -webkit-transform 0.5s ease-in-out;
  -o-transition: transform 0.5s ease-in-out;
  transition: transform 0.5s ease-in-out;
  transition: transform 0.5s ease-in-out, -webkit-transform 0.5s ease-in-out;
}

.sidebar > div {
  height: 100%;
  width: 100%;
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-orient: vertical;
  -webkit-box-direction: normal;
      -ms-flex-direction: column;
          flex-direction: column;
  -webkit-box-align: center;
      -ms-flex-align: center;
          align-items: center;
  -webkit-box-pack: center;
      -ms-flex-pack: center;
          justify-content: center;
  color: #fff;
}

.sidebar h1 {
  font-size: 40px;
  margin-bottom: 10px;
  margin-top: -30px;
}

.main-slide {
  height: 100%;
  position: absolute;
  top: 0;
  left: 35%;
  width: 65%;
  -webkit-transition: -webkit-transform 0.5s ease-in-out;
  transition: -webkit-transform 0.5s ease-in-out;
  -o-transition: transform 0.5s ease-in-out;
  transition: transform 0.5s ease-in-out;
  transition: transform 0.5s ease-in-out, -webkit-transform 0.5s ease-in-out;
}

.main-slide > div {
  background-repeat: no-repeat;
  background-size: cover;
  background-position: center center;
  height: 100%;
  width: 100%;
}

button {
  background-color: #fff;
  border: none;
  color: #aaa;
  cursor: pointer;
  font-size: 16px;
  padding: 15px;
}

button:hover {
  color: #222;
}

button:focus {
  outline: none;
}

.container .controls button {
  position: absolute;
  left: 35%;
  top: 50%;
  z-index: 100;
}

.container .controls .down-button {
  -webkit-transform: translateX(-100%);
      -ms-transform: translateX(-100%);
          transform: translateX(-100%);
  border-top-left-radius: 5px;
  border-bottom-left-radius: 5px;
}

.container .controls .up-button {
  -webkit-transform: translateY(-100%);
      -ms-transform: translateY(-100%);
          transform: translateY(-100%);
  border-top-right-radius: 5px;
  border-bottom-right-radius: 5px;
}