In the game engine, I've created a door handle and door, and am trying to combine the physics in the logic editor so that when I left click on the door handle, it spins, meanwhile also swinging open the door at 120 degrees. To summarize my problem, when I select two objects, I can't get both under logic editor, and they end up having the same qualities. How do I separate them?
What your final result may look like:
You can link the logic-bricks of different objects if you select both of these objects in the 3d-view.
In my example, I use a mouse-over and a left-button sensor to detect a click on the handle. That goes to an and-controller, which is connected to both the armature of the door and the armature of the handle. Both armatures then play their animation.
Inter-object connections are possible, but make your logic bricks really complex.
I assume you do not need very short reaction time on the mouse click. Therefore I suggest to communicate via messages. As additional benefit you can have any number of different door openers. (Button press, mouse click, joystick button, automatic door opener ...)
Sensing when to open the door
The sole purpose of this logic is to send a message whenever the door should be opened. To differentiate the message from other message you set a meaningful subject such as "open door". Be aware when you have more than one door you should tell what door to open: "open door A" vs "open door B".
on door handle (of door A)
Sensor Mouse over Sensor Mouse left button Controller AND Actuator Message subject "open door A"
Opening the door
Your door and you handle or door A should both listen to a message "open door A".
handle: Sensor Message subject "open door A" Controller AND Actuator Action ->play handle turning action.
door wing: Sensor Message subject "open door A" Controller AND Actuator Action -> play wing opening action.
Both receive the message at the same time. This results in playing both actions at the same time. I guess this is what you want.