:beetle: Fix dispersion computation

Negative dispersion was impossible before fix.

labs/cascade/Arena1.tscn

@@ -7,9 +7,9 @@
 [node name="Arena1" type="Node"]
 
 [node name="Spawner" type="Position2D" parent="."]
-position = Vector2( 844.767, 116.097 )
+position = Vector2( 834.385, 167.066 )
 script = ExtResource( 3 )
-dispersion_scale = Vector2( 10, 10 )
+dispersion_scale = Vector2( 40, 40 )
 delay = 0.1
 
 [node name="Bar" parent="." instance=ExtResource( 1 )]

labs/cascade/component/spawner/Spawner.gd

@@ -11,9 +11,8 @@ func _ready():
 
 
 func spawn():
-	print("spawn")
 	var ball: PhysicsBody2D = Ball.instance()
-	var dispersion = Vector2(randf() * dispersion_scale.x, randf() * dispersion_scale.y)
+	var dispersion = Vector2(rand_range(-1.0, 1.0) * dispersion_scale.x, rand_range(-1.0, 1.0) * dispersion_scale.y)
 	ball.position = dispersion
 
 	add_child(ball)