* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
html, body {
height: 100%;
}
.flex-container {
  display: flex;
  background-color: darkslategray;
  justify-content: center;
  align-items: center;
  width: 100%;
  height:100%;
}
.audio1 {
  position: absolute;
}