Kadath

I don't understand why we have to use the scroll bar to aim instead of just letting him us at our mouse.

You can aim by clicking and holding anywhere on the screen above the bar, you don't have to be touching the bar directly. The reason for no mouse aiming is because of catapult controls. The bullet travels in an arc , so click-to-aim would be misleading, as you wouldn't be aiming where the cursor is pointing but slightly above/below. Think Angry Birds.