2015-06-22 : Any red instant or sorcery spell you spend the mana on will be copied, not just one that requires targets.

2015-06-22 : If a copy is created, you control the copy. That copy is created on the stack, so it’s not “cast.” Abilities that trigger when a player casts a spell won’t trigger. The copy will then resolve like a normal spell, after players get a chance to cast spells and activate abilities.

2015-06-22 : If more than one red mana produced by a Pyromancer’s Goggles is spent to cast a single red instant or sorcery spell, the delayed triggered ability associated with each mana spent will trigger. That many copies will be created. It doesn’t matter if this red mana was produced by one Pyromancer’s Goggles or by multiple Pyromancer’s Goggles.

2015-06-22 : If the copied spell has an X whose value was determined as it was cast, the copy has the same value of X.

2015-06-22 : If the copied spell is modal (that is, it says “Choose one –” or the like), the copy will have the same mode. You can’t choose a different one.

2015-06-22 : If the copy says that it affects “you,” it affects the controller of the copy, not the controller of the original spell. Similarly, if the copy says that it affects an “opponent,” it affects an opponent of the copy’s controller, not an opponent of the original spell’s controller.

2015-06-22 : The copy will have the same targets as the spell it’s copying unless you choose new ones. You may change any number of the targets, including all of them or none of them. If, for one of the targets, you can’t choose a new legal target, then it remains unchanged (even if the current target is illegal).

2015-06-22 : The delayed triggered ability will trigger whether Pyromancer’s Goggles is still on the battlefield or not.

2015-06-22 : The mana produced by Pyromancer’s Goggles can be spent on anything, not just a red instant or sorcery spell.

2015-06-22 : You can’t choose to pay any additional costs for the copy. However, effects based on any additional costs that were paid for the original spell are copied as though those same costs were paid for the copy too. For example, if you sacrifice a 3/3 creature to cast Fling, and you copy it, the copy of Fling will also deal 3 damage to its target.