This one just occurred to me as a result of the thread about threatening roar, where cropz pointed out that you can activate it when the opponent intends to exit Main Phase 1. Here's my question: What is the exact timing window for determining if a Battle Phase will be conducted or not? Example: Enter Main Phase 1, P1 elects to kick it off by summoning Gemini Elf. Response window, both players pass. Non-responsive window, P1 passes, AKA declares his wish to exit Main Phase 1. At this point, does he say if he intends to conduct a Batte Phase? Or does he wait until AFTER P2 has passed, where an infinitessimal timing window occurs to determine if there will be a Battle Phase? And, if it is the former and not the latter, let's suppose the opponent did NOT pass. Let's suppose he activated something that CHANGED P1'S MIND about whether he wants a Battle Phase. Now what? Do we resolve the current chain, have another opportunity for response, and then repeat the process? Or is he bound to the decision previously made? I'm inclined to believe an infinitessimal window occurs for this decision, to prevent the arguments that may occur if it were not for this window. But I wouldn't know.