I've looked around for clues to solve my problem but have had no luck in finding a complete answer. Forgive me if this is a trivial problem to solve :-)

I've been experimenting with the Locomotion System extension of Unity, inside the context of a 2.5D parallax scrolling game. I would like to create an aiming system similar in style to the game "Capsized" (see link below), whereby the character's weapon follows the mouse position on the screen and through some form of IK manipulation the character's body follows along in rotation and such. So if the mouse travels positive or negative on the Y axis the character's gun > arms > body > etc. transforms (I guess rotation would be desired) along, and if the mouse travels positive or negative on the X axis crossing over the character, the character will turn or rotate along with it while still keep animation and movement. For example if the character is running forward and the mouse is positive on the X axis the character will be aiming forward, yet if the mouse travels negative on the X axis but the character is still moving forward they will rotate and transition into a backward run (which I'm assuming will be handled by the Locomotion System). I hope all this makes sense; any help would be greatly appreciated.

http://www.youtube.com/watch?v=SrYUEa00dGM