Forging Gold copies now costs Moondust, not Moonglass. Moondust is shown in the menu, and one button grinds all spares.
Other changes
Forging: 3 normal copies + Moondust become 1 Gold copy. Price: Common 50, Uncommon 100, Rare 250, Epic 600, Legendary 1500 Moondust (ten times what grinding one copy gives). Moonglass is no longer used for forging.
Why: Gold copies are a reward for playing and collecting. Moondust comes from cards you already own, so every player can forge without buying anything.
Your Moondust is shown in the main menu next to Silver and Moonglass, and in the collection.
New in the collection: "Grind spares" grinds all spare copies of one rarity (Common, Uncommon, Rare, Epic, Legendary) or of all rarities at once. The window shows how many copies and how much Moondust before you confirm. You always keep 2 copies of each card for decks (Legendary 1) and every Gold copy.