If “UFOroid” attacks an Attack Position “Pyramid Turtle”, first the turn player decides whether to activate the effect of “UFOroid” or not, and if he does, it will be Chain Link 1. If he doesn’t, the opponent has a chance to activate “Pyramid Turtle’s” effect and be Chain Link 1. If he does, it is too late for the turn player to decide to activate “UFOroid’s” effect.
If you do not choose to Special Summon a Machine, this card’s effect will not activate or start a chain.