The gun cannot affect most organic material, though there are a few exceptions. The secondary fire can only pick up lighter objects - mainly those which Gordon himself can carry, with some exceptions - but the primary fire is capable of pushing much larger objects even if the secondary fire cannot affect them. These objects can then either be dropped by pressing the secondary fire button a second time, or they can be launched forward with the primary fire. The secondary fire pulls objects towards the gun, and holds them just ahead of the device. This is useful in-game for clearing out barriers, or moving objects that cannot be picked up, such as disabled cars. The primary fire releases an energy blast, which pushes the targeted object with a tremendous force. Alyx introducing the Gravity Gun to Gordon at Black Mesa East.
