TO SQUASH: better ball collisions.

Assets/Scripts/Game/BallSpawner.cs

@@ -22,6 +22,8 @@ public class BallSpawner : MonoBehaviour
 
     private Queue<System.Action> ballQueue = new Queue<System.Action>();
 
+    private Queue<GameObject> balls = new Queue<GameObject>();
+
     // Start is called once before the first execution of Update after the MonoBehaviour is created
     void Start()
     {
@@ -46,7 +48,9 @@ public class BallSpawner : MonoBehaviour
         }
 
         Vector3 spawnPosition = GetRandomPositionInsideGameBoard();
-        Instantiate(ballPrefab, spawnPosition, Quaternion.identity);
+        var newBall = Instantiate(ballPrefab, spawnPosition, Quaternion.identity);
+
+        balls.Enqueue(newBall);
     }
 
     private Vector3 GetRandomPositionInsideGameBoard()
@@ -70,8 +74,9 @@ public class BallSpawner : MonoBehaviour
             bounds = boardRenderer.bounds;
         }
 
-        float randomX = Random.Range(bounds.min.x, bounds.max.x);
-        float randomY = Random.Range(bounds.min.y, bounds.max.y);
+        const float edgeInset = 0.05f;
+        float randomX = Random.Range(bounds.min.x + edgeInset, bounds.max.x - edgeInset);
+        float randomY = Random.Range(bounds.min.y + edgeInset, bounds.max.y - edgeInset);
 
         return new Vector3(randomX, randomY, gameBoard.transform.position.z);
     }
@@ -84,5 +89,32 @@ public class BallSpawner : MonoBehaviour
             spawnAction.Invoke();
             yield return _waitForSeconds0_5;
         }
+
+        // Disable collision between existing balls of certain types.
+        // Only basic balls and fruit balls will collide with each other, while ooze,
+        // nuclear, glass, and eye balls will not collide with any other balls.
+        // As an exception, glass balls will collide with other glass balls.
+        foreach (var ball in balls)
+        {
+            foreach (var otherBall in balls)
+            {
+                if (ball == otherBall) continue;
+
+                bool ballIsBasicOrFruit = ball.CompareTag("BasicBall") || ball.CompareTag("FruitBall");
+                bool otherIsBasicOrFruit = otherBall.CompareTag("BasicBall") || otherBall.CompareTag("FruitBall");
+                bool bothAreGlass = ball.CompareTag("GlassBall") && otherBall.CompareTag("GlassBall");
+
+                bool shouldCollide = (ballIsBasicOrFruit && otherIsBasicOrFruit) || bothAreGlass;
+
+                if (!shouldCollide)
+                {
+                    Physics2D.IgnoreCollision(
+                        ball.GetComponent<Collider2D>(), 
+                        otherBall.GetComponent<Collider2D>(), 
+                        true
+                    );
+                }
+            }
+        }
     }
 }