Your first 2D game: Set the physics parameters of the mob before addi…

…ng it to the scene tree

This follows the recommendation from godotengine/godot#45638

getting_started/first_2d_game/05.the_main_game_scene.rst

@@ -322,14 +322,13 @@ Note that a new instance must be added to the scene using ``add_child()``.
  .. code-tab:: gdscript GDScript
 
     func _on_MobTimer_timeout():
+        # Create a new instance of the Mob scene.
+        var mob = mob_scene.instance()
+
         # Choose a random location on Path2D.
-        var mob_spawn_location = get_node("MobPath/MobSpawnLocation");
+        var mob_spawn_location = get_node("MobPath/MobSpawnLocation")
         mob_spawn_location.offset = randi()
 
-        # Create a Mob instance and add it to the scene.
-        var mob = mob_scene.instance()
-        add_child(mob)
-
         # Set the mob's direction perpendicular to the path direction.
         var direction = mob_spawn_location.rotation + PI / 2
 
@@ -340,26 +339,28 @@ Note that a new instance must be added to the scene using ``add_child()``.
         direction += rand_range(-PI / 4, PI / 4)
         mob.rotation = direction
 
-        # Choose the velocity.
+        # Choose the velocity for the mob.
         var velocity = Vector2(rand_range(150.0, 250.0), 0.0)
         mob.linear_velocity = velocity.rotated(direction)
 
+        # Spawn the mob by adding it to the Main scene.
+        add_child(mob)
+
  .. code-tab:: csharp
 
     public void OnMobTimerTimeout()
     {
         // Note: Normally it is best to use explicit types rather than the `var`
         // keyword. However, var is acceptable to use here because the types are
-        // obviously PathFollow2D and Mob, since they appear later on the line.
+        // obviously Mob and PathFollow2D, since they appear later on the line.
+
+        // Create a new instance of the Mob scene.
+        var mob = (Mob)MobScene.Instance();
 
         // Choose a random location on Path2D.
         var mobSpawnLocation = GetNode<PathFollow2D>("MobPath/MobSpawnLocation");
         mobSpawnLocation.Offset = GD.Randi();
 
-        // Create a Mob instance and add it to the scene.
-        var mob = (Mob)MobScene.Instance();
-        AddChild(mob);
-
         // Set the mob's direction perpendicular to the path direction.
         float direction = mobSpawnLocation.Rotation + Mathf.Pi / 2;
 
@@ -373,19 +374,21 @@ Note that a new instance must be added to the scene using ``add_child()``.
         // Choose the velocity.
         var velocity = new Vector2((float)GD.RandRange(150.0, 250.0), 0);
         mob.LinearVelocity = velocity.Rotated(direction);
+
+        // Spawn the mob by adding it to the Main scene.
+        AddChild(mob);
     }
 
  .. code-tab:: cpp
 
     // This code goes in `main.cpp`.
     void Main::_on_MobTimer_timeout() {
+        // Create a new instance of the Mob scene.
+        godot::Node *mob = mob_scene->instance();
+
         // Choose a random location on Path2D.
         _mob_spawn_location->set_offset((real_t)_random->randi());
 
-        // Create a Mob instance and add it to the scene.
-        godot::Node *mob = mob_scene->instance();
-        add_child(mob);
-
         // Set the mob's direction perpendicular to the path direction.
         real_t direction = _mob_spawn_location->get_rotation() + (real_t)Math_PI / 2;
 
@@ -399,6 +402,9 @@ Note that a new instance must be added to the scene using ``add_child()``.
         // Choose the velocity for the mob.
         godot::Vector2 velocity = godot::Vector2(_random->randf_range(150.0, 250.0), 0.0);
         mob->set("linear_velocity", velocity.rotated(direction));
+
+        // Spawn the mob by adding it to the Main scene.
+        add_child(mob);
     }
 
 .. important:: Why ``PI``? In functions requiring angles, Godot uses *radians*,