darkhog, Good idea, I think to make the NPC Debug tool and tiny code constructor, which will help you for create the npc's code and test npc in the debugger. Debugger will have event emulator and tests of detectors. For example, by mouse click set "player's position" and test movement algorithm of the NPC and reaction on the environment and contacts with other objects, etc. If NPC is flying, it will not have the gravity, but you can program movement style. For example, parakoopas moving horizontal by sine path. If parakoopa is chasing, it will fly to the player's position by x-y coordinates. But, it will turn with acceleration/deceleration of speed, and its vector always directed to a player's position. Also, playable character coordinated will be captured from nearly playable character in the multilayer mode.