Can Temporal Portal repeat the effect of a card played from Hidden (like Fox Fire) with 0 cost, since it doesn't specify 'base cost'?

Ruling: Whenever card text says "cost" it means the base cost of a card. Temporal Portal looks at the printed cost, so a card played from Hidden with 0 cost cannot be repeated by Temporal Portal since its base cost is higher.

Nuances:

• A card reduced in cost (like Skysplitter reduced to 4 energy) still has its original base cost for card effects
• With Hidden, you would pay for one cast and get one free from the Hidden effect, but Temporal Portal would not trigger an additional repeat