Forge's Awesome AI

It's been awhile since I've talked about "Forge's awesome AI". Basically Forge's AI is very simple. Each spell and ability has a method called canPlayAI() which returns true if the AI should play it. Royal Assassin's ability is a good example. The AI for Royal Assassin's activated ability checks to see if you have any tapped creatures and then targets the biggest one. Shock does about the same thing, except that the code tries to kill X/2 flyers and 3/1 creatures and avoids plain 2/2.

The biggest flaw of canPlayAI() is that each card and ability is evaluated separately. The computer will never use two Shocks to kill a 4/4. Since each card is evaluated individually it is hard to create decks that the AI can use effectively. Generally the AI is good with creatures and basic, aggro decks. One of the decks that I submitted as a deck for the quest AI had all vampire creatures, it did not include any sorceries or instants. Some of the vampires had effects that trigger when you play them, which acted like sorceries. The AI could use the deck because it only had to play creatures and then attack.

Combat is handled completely separate. The attacking code tries to be aggressive and will usually attack. Sometimes the AI should attack but is too cautious, thus causing the game to stretch out. (I tried to avoid problem of when the AI would attack with everything and then you would attack and win but I accidentally caused this "stalling" problem.)

The blocking code is also very simple. The AI tries to make decent blocking decisions. The blocking code is more complicated than the attacking code since you can have multiple blockers and generally you don't want flyers to block non-flyers.

The attacking and blocking code does not do anything fancy and just uses a "for" loop to generate which creatures will attack or block. Let me explain the "for" loop for the attacking code. The code looks at each of the computer's creatures individually and asks, "Should this creature attack?" The blocking code does to the same thing, it looks at each attacking creature and asks, "Should this creature be blocked?"

Obviously this isn't how a human player attacks or blocks. Players, like myself, attack or block based on the whole combat situation, all of the creatures. So the AI does very little processing when it comes to combat and that explains why it makes so many mistakes in that area. Ideally the AI would do a CPU intensive search to generate better combat decisions.

Forge's biggest snafu is that the AI doesn't play spells during your turn, except for counterspells, or during combat. This was done to simple the code for canPlayAI(). Coding canPlayAI() for "normal" situations is hard, so coding for unusual situations (like other phases) is out of the question.

The biggest strength of Forge's AI is that it plays by the rules, nothing fancy. On paper it sounds easy until you begin coding and then you start pulling you hair out. Making the AI use the same resolve code as the player is very hard. (Forge's early design dictated that I had to code each card twice. One for the player and one of the computer. I knew this was the wrong way to go.)

For awhile Wagic's AI couldn't use activated abilities and I knew exactly how hard I worked on that. (Unfortunately it is hard to help someone because different projects have different UML designs, how everything fits together.)

p.s.
By the way, Wagic is a great project. It has more cards than Forge and a nice user interface. Shoutouts to wololo. (The guy who started Wagic.)

p.p.s.
And as a side issue, Forge still uses the "old combat" rules.