I was wondering if anyone could point me to a tutorial or help me with a question. I have built a tank and want to start out a very simple game where you can drive the tank and and the turret on top can spin and shoot. Now my question is, how can i make projectiles that continue in the same direction that the cannon shot it, but then be able to spin the cannon while the first shot is in the air. Basically i want to be able to shoot the cannon while it is spinning. Thanks for any help you can give. 
What you want to do is have the shell the cannon will fire in another layer. Do this by pressing, say, 2 while the mouse is in the normal view. When the cannon fires the shell, you want it to ADD the shell using an add object actuator (make an actuator, choose edit object, then select add object from the list. Type the shells name in the object box.)
Now, you should be able to add whatever spins or movement to the cannon without disturbing the shell. You can put some type of motion actuator on the shell to make it look like its been fired when you add it, or you can program in some movement to the add object actuator.
Thanks for the reply and i’ll fiddle around with what you said and see what i can come up with, thanks again.