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

body {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
}

p {
  margin:20px;
  font-size:2em;  
}

#container{
  position:relative;
  width:600px;
  height:300px;
  border:2px solid #ccc;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.arrow {
  z-index:100;
  font-size:2em;
  padding:10px;
  background:#ddd;
  color:#222;
  opacity:0.2;
}

.arrow:hover {
  opacity:1;
}