Solutions involve objects' physical properties, such as shape, weight, and buoyancy. Instead of button-based puzzles from Half-Life, environmental puzzles are also introduced with makeshift mechanical systems, revolving around the player's new ability to pick up, move, and place objects.
Two sections of the game involve driving vehicles. Many of the game's new features utilize its detailed physics simulation. Squad members are indicated on the HUD (squad member icons with a cross sign are field medics).
At one point in the game, Gordon can be joined by up to four armed Resistance soldiers, and can send his team further from him or call them back however, they can still die easily due to lack of damage protection. Gordon can kill most enemies with his weapons, or make use of indirect means, exploiting environmental hazards such as explosive pressurized canisters, gas fires or improvised traps.
