Oh thanks Mouledoux! Well, in various reasons; 1) The comets (plus some spaceships) will respawn/destroy during runtime too. Whether the player hits them or they are out of screen. I figure it will be more organized to add their attack pattern only if they exist in the game. 2) Testing and debugging – if anything comes up, at least I can only deal with a specific script and dont need to mess up with my main. This <addComponent> line can be a comment and voila~ I can check if my main script is bug free or other scripts are conflicting with others.