Added new enemy ships. Cleaned up enemy code.

AlientAttack.MonoGame/Things/Enemies/EnemyShip.cs

@@ -1,6 +1,67 @@
-namespace AlienAttack.MonoGame.Things.Enemies;
+using AlienAttack.MonoGame.Things.Bullets;
+
+namespace AlienAttack.MonoGame.Things.Enemies;
 
 public abstract class EnemyShip(int x, int y) : MoveableSprite(x, y)
 {
+    protected abstract int Health { get; set; }
+
     public virtual int CrashDamage => 10;
+
+    public override sealed void Update(SpriteUpdateContext context)
+    {
+        if (Health <= 0)
+        {
+            IsDead = true;
+            SpawnExplosion(context);
+            OnKilled(context);
+            return;
+        }
+
+        base.Update(context);
+
+        TryMove(context);
+
+        if (YPosition > context.ViewTransform.ScreenHeight)
+        {
+            IsDead = true;
+            return;
+        }
+
+        TryFire(context);
+    }
+
+    protected virtual void TryMove(SpriteUpdateContext context)
+    {
+
+    }
+
+    protected virtual void TryFire(SpriteUpdateContext context)
+    {
+
+    }
+
+    public override void OnCollision(SpriteCollisionContext context)
+    {
+        if (context.Sprite is Bullet bullet && bullet.Owner is Player)
+        {
+            Health -= bullet.Damage;
+        }
+
+        if (context.Sprite is Player)
+        {
+            Health = 0;
+        }
+    }
+
+    private void SpawnExplosion(SpriteUpdateContext context)
+    {
+        context.SpawnSprite(new Explosion((int)XPosition, (int)YPosition, XVelocity, YVelocity));
+        context.AudioManager.PlayExplosion();
+    }
+
+    protected virtual void OnKilled(SpriteUpdateContext context)
+    {
+
+    }
 }