I am fairly certain I know how this card works, but there was not a consensus among the judges at the Sneak Preview about it, so I wanted to get official word.
Concerning the promo card "Gemini Summoner":
Gemini Summoner:
Oncer per turn, during your opponent's End Phase, you can pay 500 Life Points to Normal Summon or Set 1 Gemini monster from your hand or Normal Summon 1 face-up Gemini monster you control. Once per turn, if this card would be destroyed by battle, it is not destroyed. (Damage calculation is applied normally.)
Specifically, the highlighted text.
I assume that it is like "Gyroid" and would not be destroyed by battle (the first time) even if it was face-down when attacked (continuous modifier and all). However, some of the judges/players wondered if it was like "D. D. Survivor" and had to be face-up when attacked to get the effect.
Answer:
This effect of "Gemini Summoner" will be applied even when "Gemini Summoner" is flipped face-up by the attack.
It is like "Gyroid".
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Curtis Schultz
UDE Netrep
CurtisSchultz_Netrep@hotmail.com