Gravity gun

Gravity Gun
A gravity gun model from Half-Life 2.
First game	Half-Life 2 (2004)
Created by	Gabe Newell
Designed by	Gabe Newell,Marc Laidlaw

A gravity gun is a type of device in video games, particularly first-person shooters using an advanced physics engine, whereby players can directly manipulate objects in the world, often allowing them to be used as projectiles against hostile characters. The concept was first featured in the third-person shooter Psi-Ops: The Mindgate Conspiracy which, while not featuring a dedicated 'gravity gun', allows the player to use telekinesis to manipulate both objects and enemies by moving them or forcefully throwing them around.

The concept was popularized by the gravity gun found in Valve's Half-Life 2, as well as the Temporal Uplink found in Free Radical Design's TimeSplitters: Future Perfect; although a similar concept was used by id Software during the production of the earlier game Doom 3, eventually leading to the introduction of a physics-based weapon in the expansion pack Resurrection of Evil. Later games, such as Portal, BioShock, Crysis, and Dead Space, have been influenced by the success of these physics-based weapons, adopting their own styles of comparable abilities or weapons.

Valve Software's Half-Life 2 made significant use of physics in the game, powered by the Havok engine. Although the player can pick up and throw objects early in the game, this ability is somewhat limited in scope. Around a quarter of the way through the game, the player acquires the gravity gun, properly named as the "zero-point energy field manipulator". Alyx Vance explains that the gravity gun is designed for handling hazardous materials, but is mostly used for heavy lifting. She explains to Gordon that she once found it useful "for clearing minefields". The gravity gun significantly increases the player's ability to manipulate objects in the game. Like most other weapons in the game, the gravity gun has two trigger functions. The primary trigger causes the gun to emit a small discharge which emits energy to the targeted object. The distance which the object is forced is dependent on its weight and distance from the gun. The secondary trigger attracts the targeted object to the gun and holds it in midair a few inches away, negating its weight and allowing the player to carry it with them. Using the secondary trigger again will drop the item, while the primary trigger will launch it with considerable force.