Making Co-op Work in an Open World on Edge Online is an article by Scott Phillips, where the Lead Designer on Saints Row 2 discusses the considerations that go into cooperative support in such an open-world game. The lack of multiplayer co-op in many games is ascribed to difficulties with implementation and balance, and Scott confirms that co-op support does not come easily: "It took a long, long time to get co-op into a working state. In addition to the sheer technical issues, there are obvious design issues. When an AI sees two targets, which one is he going to decide to shoot at? We also had to increase the number of AI in order to effectively balance both the single player and co-op so that there would be similar difficulty levels across both. You’ve got to scale it to some degree in order to make sure that it’s similarly difficult on both levels. We had to script new methods for each player to complete activities and missions in co-op and make that a different experience."