Hopper Mine

Hopper mine
First Seen: Half-Life 2, Chapter Eleven, Anticitizen One
 * Health total: N/A
 * Weapon damage: Detonation (splash damage)
 * Entity:

Hopper mines are anti-personnel proximity mines that hop into the air towards the target before exploding, much like a bouncing betty. These mines are carried and deployed by shield scanners. They are vaguely cone-shaped with three sharp "legs". When dropped, the mines use these legs to bounce around until they land right-ways up on a smooth surface. They then jam the legs into the ground, attaching themselves very firmly.

When an enemy target comes close, the mines light up and give off a warning chirp. If the enemy target gets too close, the mines will toss themselves unpredictably, nearly two meters (six feet) into the air, and explode upon contact with whatever they happen to hit on the way down, which is usually the ground. They also detonate if smashed too violently. Otherwise, they are impervious to nearly all forms of handheld weaponry, save for the gravity gun.

Because of their danger, immovability and extreme durability, hopper mines are impossible for most enemies to disable or defuse. Thus, they are used by the Combine almost exclusively to deter attacking enemy personnel, creating makeshift but often impassable barriers in seconds. They are used both indoors and outdoors, mostly in vital choke-points and occasionally concealed as traps.

Hopper mines use a friendly fire identification system which resets whenever they are picked up. The mines interpret a "friendly" unit as whichever faction placed it last. Thus, a mine placed by a citizen with a gravity gun will attack Combine, and a mine dropped by a shield scanner will attack citizens. This system is signaled through a color-coded light at the top of the device:
 * Green : The mine is armed and considers whoever is close to it to be a friend.
 * Red : The mine is armed and considers whoever is close to it to be an enemy.
 * Blue : The mine is neutral and has not yet armed itself.
 * Orange : The mine is in panic mode, having been rooted from the ground (with the gravity gun) and is uncontrollably attempting to re-grip the ground
 * No light: The mine has not yet been activated.

The ability to be turned against the Combine is most likely not an intentional feature of the mine or, instead, a reprogramming function built into the gravity gun, which was designed with mine removal in mind. When the gravity gun is first given to Gordon by Alyx, she mentions that she found the gun useful for clearing mine fields. Players have also theorized that this is because of a programming mistake by the Combine and that a hopper mine will consider whatever placed it last to be an ally. Based on what Alyx said, this makes more sense. In any case, the mines are unlikely to be placed by anything other than the Combine's shield scanners. If thrown using the gravity gun's primary fire, the mine explodes on contact with whatever it hits first. Alternatively, as a last-chance effort, as a mine hops in the air it may be shot away using the gravity gun's primary fire. This is particularly useful if a mine remains unnoticed until after it has hopped. In addition, if the mine can be caught by the gravity gun before hitting something, it will not explode. The legs will flail in an attempt to jump, thinking it must still be grounded. After being dropped, the mine will reset itself.