High Energy Pellet



The High Energy Pellet is a puzzle mechanic introduced in Portal. It is a fast moving energy ball, fired by an emitter built into a Test Chamber surface and usually accompanied by a receptacle that catches it. Players direct the ball into the receptacle in order to activate lifts or devices before it dissipates and explodes. The ball is extremely volatile, and as such instantly vaporizes test subjects on contact. Turrets, however, will be knocked over by it.

Portal
The High Energy Pellet was a common puzzle mechanic in Portal. It first appeared in Portal Test Chamber 06 and made recurrent appearances throughout the game. Test Chamber 19 features two versions of the High Energy Pellet, the standard yellow High Energy Pellet as well as a green High Energy Pellet. As the green one does not dissipate and explode, it is sometimes colloquially known as the Super High Energy Pellet.

Portal 2
The High Energy Pellet itself does not make an appearance in Portal 2; however, its emitter and receptacle do. These appear in Chamber 1 of Portal 2's second chapter, which is identical to Test Chamber 06 of Portal (albeit run down and degraded). However, this similarity is removed when GLaDOS replaces the items with those of the Thermal Discouragement Beam. They are also present in Chamber 7 of Portal 2's first chapter, as this chamber is simply a run-down version of Portal's Test Chamber 07. The catcher appears in the ruins of Test Chamber 19 from Portal and is visible once Chell moves towards the exit after being dropped in the incinerator.

Trivia

 * The Energy Pellet uses the Combine Energy Ball model from the Half-Life series.
 * The Pellet "refreshes" every time it passes through linked portals, meaning the player could keep the ball bouncing until they've discovered the solution to the current chamber.
 * For a brief moment in Portal 2 Chapter 2 Test Chamber 1, the High Energy Pellet launcher and catcher can be seen being replaced with the Thermal Discouragement Beam.