The player controls Isaac Clarke from a third-person perspective, looking over the character’s right shoulder. As in the previous game, the game uses the Resource Integration Gear (RIG) suit, an in-world HUD (heads-up display) system that uses holograms projected from Isaac’s suit and weapons to show information such as messages and ammunition count. In vacuum areas, a timer appears on Isaac’s right shoulder, counting how much oxygen his suit has before he suffocates. The RIG also uses gauges on Isaac’s back to display his health and stasis module levels. If Isaac’s health or air timer reaches zero, or if the player fails to survive a quick-time event, Isaac will die, forcing the player to restart from the last checkpoint.
Early in the game, Isaac acquires the stasis module, which slows down enemies and otherwise-impassable moving obstacles (e.g. active heavy machinery) to allow Isaac to pass through safely; and the kinesis module, which allows Isaac to carry and fire objects telekinetically. The player can upgrade their weapons and armor at work benches, using power nodes. There are also automated stores, where the player can buy and sell various items, and gain new weapons and suits through acquiring schematics found throughout the Sprawl.
Throughout the game, the player will come across different puzzles that impede progress. In some cases, Isaac must hack consoles to activate machines and open doors; in others, Isaac must repair or reposition mechanisms to proceed. The player regularly encounters zero-G environments, where Isaac is capable of maneuvering in all directions with thrusters attached to his suit. Both normal and zero-G environments may be in areas within the vacuum of outer space; in these situations, Isaac must refill his limited oxygen supply via oxygen dispensers.
Much like in the first game, Isaac must fight the Necromorphs, organisms that mutate and take control of human corpses. To take down Necromorphs, the player must use “strategic dismemberment”: in other words, slicing off limbs or sections of the Necromorphs’ bodies. For example, shooting a Slasher Necromorph in the head will, like many other types, have little effect; however, it can be stopped by shooting its bladed arms off. Depending on how they are wounded, some Necromorphs, like the Pregnant and the Ubermorph, can adopt new stances and tactics, even sprouting new limbs or spawning more enemies in the process.
Dead Space 2’s main campaign offers five difficulty levels (listed in order of difficulty): Casual, Normal, Survivalist, Zealot and Hard Core. Hard Core is unlocked once the game has been completed on any other difficulty. Playable only from a fresh start, Hard Core mode limits the player to three saves in the entire campaign. Item drops and credits are very difficult to find, enemies are very challenging, and checkpoints are absent.