body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
  display: flex; /* use flex to center */
  justify-content: center; /* horizontal center */
  align-items: center; /* vertical center */
  background-color: #0f0f0f;
}

#app {
  width: 100%;
  height: 100vh;
  max-width: 1440px;
  max-height: 620px;
  overflow: hidden;
  display: flex;
  justify-content: center;
  align-items: center;
}