Forge implements a huge number of cards and many of those cards are really, really complicated. Some cards are so complicated that even I didn’t think Forge would ever have like Hypnotic Specter (HP). HP is a great card but I did not have any idea how to implement him. Granted the combat code does specifically look for HP but he works and that is the only thing that really matters.
Swans of Bryn Argoll (costs: 2 W/U W/U, 4/4 flying) is another great, thorny card. Swans says, “If a source would deal damage to Swans of Bryn Argoll, prevent that damage. The source's controller draws cards equal to the damage prevented this way.” Forge is relatively “primitive” and prevention effects are complicated. I was happily surprised when I first saw Swans. Someone on the forum mentioned that Swans and Phytohydra (2GWW, 1/1) “If damage would be dealt to Phytohydra, put that many +1/+1 counters on it instead” did not correctly work together. Thankfully Sloth (one of the programmers) jumped on the case and said that the next version will fix this problem.
Pillory of the Sleepless (cost: 1WB) enchants a creature and has “Enchanted creature can't attack or block. Enchanted creature has ‘At the beginning of your upkeep, you lose 1 life.’” I have no idea how Forge implements “this creature can’t attack or block” but those cards are really fun to use. I actually won a match against the computer because of Pillory. Losing 1 life a turn isn’t usually a game-winner but in a stalemate it will tip things in your favor.
Planar Gate (cost: 6, artifact) “Creature spells you cast cost up to 2 less to cast.” Cards that arbitrarily affect other cards are the most complicated. Since Planar Gate changes mana costs for other cards, Forge has to reduce the cost of only creature spells and only creatures spells that can use any color of mana. Cards like Planar Gate are very hard to code and very fun to use.
Platinum Angel and Platinum Emperion are both great, powerhouse cards that change the winning conditions. Platinum Angel (cost: 7, 4/4) “You can't lose the game and your opponents can't win the game” and Platinum Emperion (cost: 8, 8/8) “Your life total can't change. (You can't gain or lose life. You can't pay any amount of life except 0).” Changing the winning conditions can be difficult and I’m glad that Forge was flexible enough to accommodate these cards.
Predatory Advantage (3RG, enchantment) gives you a 2/2 creature if your opponent did not play a creature, thus punishing control strategies like blue counterspell decks. This type of card needs to know the game’s “history” and whether a creature was played. “History cards” can be complicated and Forge has a simple history class that holds information about what happened during the current and previous turn.
Thanks for reading,
p.s. Recently I’ve been watching “Hogan’s Heroes” and even though it is 40 years old, it is a great show. It's even in color!