so ... less bugs, moar AIs

I just fixed some small but annoying bugs, fixed the elemental effect (ice and fire counters each other.), made sure the AI didn't cast spells in just a single lane, and added actual difficulty levels.

Just to prevent any misconception about the AI in that game at this particuolar moment in time : any hint of intelligence you might think to detect is a figment of your imagination. All the AI does is to randomly use cards on random lanes. The difficulty level only controls the speed at which this can happens and how long the pause between AI actions can be, but the AI doesn't check where it would be best to cast a spell or whether using a fast unit might be wiser than using a slower but stronger unit in a certain lane (Something YOU should do by the way. playing randomly often works if you are faster than the computer, but using basic tactics really helps.)

so .. anyway... enjoy :)