Forum:Once per turn vs flip face down

So my buddy and I can in an interesting debate and were both stumped on a ruling. If he uses Red-eyes Darkness Metal to bring back a dragon then uses book of moon to flip it face down, then changes his battle position back to face up, he can then use the effect.

Now if you have Guardian Sphinx and you have it in face up. You flip it face down with its effect, then flip it face up to use its effect, can you flip it face down again?

Sphinx effect says once per turn, so its assumed it can only be flipped down once that turn. But darkness says once per turn, and if is flipped summoned after being set by book of moon, he is able to use his effect a second time that turn, even though it says once per turn.

Can someone help me straighten this out?

Grazzingcow (talk • contribs) 20:41, September 9, 2011 (UTC)