Neo Galaxy-Eyes Photon Dragon

The monster effect "When this card is Xyz Summoned using 'Galaxy-Eyes Photon Dragon' as material: Negate the effects of all other face-up cards currently on the field" is a Trigger Effect. (This effect does not target. It is applied to all face-up cards on your and your opponent's fields at the time the effect resolves.)

Cards whose effects are negated by the monster effect "Negate the effects of all other face-up cards currently on the field" remain negated as long as they remain face-up on the field.

The monster effect "Once per turn: You can detach 1 Xyz Material from this card; detach all Xyz Materials from your opponent's field, and if you do, this card gains 500 ATK for each, also this card can attack up to that many times during each Battle Phase this turn" is an Ignition Effect. (This effect does not target. Detaching 1 Xyz Material from this card is a cost to activate this effect.)

The process of "detach all Xyz Materials from your opponent's field" and the process of "this card gains 500 ATK for each, also this card can attack up to that many times during each Battle Phase this turn" are not treated as occurring simultaneously.

The process of "this card gains 500 ATK for each" is applied based on the number of Xyz Materials detached by the "detach all Xyz Materials from your opponent's field" process. (This does not include the Xyz Material detached as a cost to activate the effect.)