Additional Rules from the Rulebook
Draw a card first. Then, you must trash a card from your hand and gain a card costing exactly 1 coin more than the trashed card. The gained card has to be a card in the Supply, and it goes into your discard pile. If there are no cards available for that cost, you do not get one (you still trashed a card though). If you do not have a card in your hand to trash, you neither trash nor gain a card. Card costs are affected by Bridge. Since Bridge affects the costs of the card you trash and the card you gain, in most cases the Bridge will have no net effect. But since cards cannot go below zero in cost, a Bridge played before an Upgrade would allow you to trash a Copper (cost of zero, even with the Bridge) and gain an Estate (cost of 1 as a result of the Bridge).
The Secret History of Upgrade
In an article on Board Game Geek, Donald X. Vaccarino commented on the development of Upgrade:
- A very old card. I explained how it once cost 4 in the entry for Great Hall. The "exactly" part actually makes the card better, as it lets you trash Curse and Copper without gaining anything.