Time for action – adding background music

Let's get started with a single script to control our background music.

1. We will start by creating a new script and naming it FadeIn.
2. This script begins with three variables. The first is the goal volume that the script has to reach. The second is the number of seconds the transition will take. The last is the time when the transition began.

   public float maxVolume = 1f;
   public float fadeLength = 1f;
   private float fadeStartTime = -1f;

3. Next, we make use of the Awake function. It begins by looking at the audio variable, which is automatically supplied by Unity, to check for an attached Audio Source component. If one cannot be found, the gameObject is destroyed and the function is exited.

   public void Awake() {
     if(audio == null) {
       Destroy(gameObject);
       return;
     }

4. The Awake function ends by setting its volume to 0 and playing it if it isn't already.

     audio.volume = 0;
   
     if(!audio.isPlaying)
       audio.Play();
   }

5. To cause the transition...