Rotate our formation.

rotation.swift

func moveIntoFormation() {

    // Loop over each unit in our Squad.
    for (i, unit) in enumerate(self.units) {
    
        // Get the vector from the formation class for that position. 
        // Just a simple accessor to the array.
        let vector = self.formation!.getVectorAtPosition(i)
        
        // Hard coded rotation by radian of 0.4.
        var newX  = vector.dx * cos(0.4) - vector.dy * sin(0.4);
        var newY = vector.dx * sin(0.4) + vector.dy * cos(0.4);

        // Make a CGPoint from the new X & Y, and tell the unit to walk to it.
        let position = CGPoint(x:newX, y:newY)
        unit.moveToPoint(position, callback: {
            // clean up post animation
        })
    }
}