“Defying Gravity” is a single player mini-level designed for Half-Life 2: Episode Two. The purpose of this level was to use scripting to create gameplay that was "outside the box" of the engine's typical mechanics. To achieve this, the level combines 2D platformer elements from Mega Man with the bouncing ball mechanic of Breakout.

The game takes place in an unnamed city overrun with Combine soldiers. The player moves through a rundown alley littered with debris in an effort to find safety. They must jump over and across obstacles to move through the environment.

The player uses an AR2 rifle to shoot Combine Energy Balls. The glowing orb destroys any enemy it contacts. The energy ball also bounces off objects within the environment, but detonates explosive barrels on contact.