I have a non-released game, and currently it's only possible to play with another human being. As the game rules are made up by me, I think it would be great if new players could learn basic game play by playing against an AI opponent. I mean it's not like Tennis, where the majority knows at least the fundamental rules.

On the other hand, I'm a bit concerned that this AI implementation can be quite complex. I hope you can help me with an complexity estimation. I've tried to summarize the gameplay below. Is this defense AI very hard to do?

Basic Defense Game Play

Player Defender can move within his land, i.e. inside a random, non-convex, polygon. This land will also contain obstacles modeled as polygons, that Defender has to move around. Player Attacker has also a land, modeled as another such polygon.

Assume that Defender shall defend against Attacker. Attacker will then throw a thingy towards Defender's land. To be rewarded, Attacker wants to hit Defender's land, and Defender will want to strike away the thingy from his land before it stops to prevent Attacker from scoring.

To feint Defender, Attacker might run around within his land before the throw, and based on these attacker movements Defender shall then continuously move to the best defense position within his land.