The top tank is in "arcade" mode, where the Point of View (POV) is above the tank.
The second tank is in "sniper" mode, where the POV is at the base of the gun.
The pink reticle is where you think you're pointing (at the enemy tank), and the green reticle is where you're REALLY pointing (at the closest object to your "eye")
In sniper mode (bottom), the gun is pointed at whatever you point the mouse at. Since the LOS and the gun pivot from the same spot, the gun points where the mouse points.
In arcade mode (top), the gun is also pointed at whatever you point the mouse at. Since the LOS and the gun pivot are NOT in the same spot, however, there can be a strange artifact. The closest thing to your "eye" is the wall.
So in both cases, the gun points at the wall, right where your mouse is pointed. Unfortunately this isn't really what you wanted, and that's why everyone recommends either switching to sniper mode when playing peekaboo, or holding down the right-mouse-button to lock the gun in place until while taking into cover.

-Slick









