Waves of Enemies

The enemies now come in waves, and the waves are data. Keep everything from the earlier lessons. The arena has no enemies of its own any more: the Grunt and Dasher prefabs carry your scripts, four spawn points stand in the corners, and the Spawner object in the middle has the WaveSpawner script.

• In WaveSet.cs, add a [System.Serializable] class Wave with public Enemy enemy (the prefab), public int count and public float spacing. WaveSet is a ScriptableObject with [CreateAssetMenu], a public List<Wave> waves and a public float restBetweenWaves. The scene's Arena asset holds three waves (3 grunts 0.5 s apart, 2 dashers 1 s apart, 5 grunts 0.4 s apart) and a rest of 2 seconds.
• Enemy gets public static event Action<Enemy> Died, raised with the enemy right before it is destroyed.
• WaveSpawner has waveSet and spawnPoints from the Inspector, and public int Wave { get; private set; }, the number of the wave in play. From Start, a coroutine runs the asset's waves in order. For each: add 1 to Wave and log it, as Wave 1; spawn the wave's count enemies spacing seconds apart, enemy i (from 0) at spawnPoints[i % spawnPoints.Length]; wait until no enemy is left alive; then rest restBetweenWaves seconds. After the last wave the set starts again from its first, and Wave keeps counting: 4, 5 and so on.
• Count the enemies alive with the Died event: subscribe in OnEnable and unsubscribe in OnDisable. The spawner only reads the asset: in the Editor, a change made to an asset while the game runs stays in the asset after Play.

Press Play and survive a few waves, then Check.