body {
  background: black;
}

.container {
  display: flex;
  align-items: center;
  justify-content: center;

  position: absolute;
  margin: auto;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  padding: 10px;  
}

.arrayelement {
  background: blue;
  width: 50px;
  height: 50px;

  text-align: center;
}

.sort-button {
  background: blue;
  width: 100px;
  height:30px;
  border-radius: 25% 25% 50% 50%;

  position: absolute;
  margin: auto;
  top: 75%;
  left: 50%;
  transform: translate(-50%, -50%);
}