No Man’s Sky is an action-adventure survival game played from a first or third person perspective that allows players to engage in four principal activities: exploration, survival, combat, and trading. The player takes the role of a specimen of alien humanoid planetary explorer, known in game as the Traveller, in an uncharted universe. They start on a random planet near a crashed spacecraft at the edge of the galaxy, and are equipped with a survival exosuit with a jetpack, and a “multitool” that can be used to scan, mine and collect resources as well as to attack or defend oneself from creatures and hostile forces. The player can collect, repair, and refuel the craft, allowing them to travel about the planet, between other planets and space stations in the local solar system, engage in space combat with alien factions, or make hyperspace jumps to other star systems. While the game is open ended, the player may follow the guidance of the entity known as the Atlas to head towards the centre of the galaxy.
The defining feature of No Man’s Sky is that nearly all parts of the galaxy, including stars, planets, flora and fauna on these planets, and sentient alien encounters, are created through procedural generation using deterministic algorithms and random number generators from a single seed number. This 64-bit value leads to there being over 18 quintillion[b] (1.8×1019) planets to explore within the game. Very little data is stored on the game’s servers, as all elements of the game are created through deterministic calculations when the player is near them, assuring that other players will see the same elements as another player by travelling to the same location in the galaxy. The player may make temporary changes on planets, such as mining resources, but these changes are not tracked once the player leaves that vicinity. Only some “significant” changes, such as destroying a space station, are tracked for all players on the game’s servers. The game uses different servers for the PlayStation 4 and Windows versions.
Through exploration, the player is credited with “units”, the in-game currency, by observing not-yet-seen planets, alien bases, flora and fauna in their travels. If the player is first to discover one of these, they can earn additional units by uploading this information to the Atlas, as well as having their name credited with the discovery to be seen by other players through the game’s servers. Players also have the opportunity to rename these features at this point within limits set by a content filter. No Man’s Sky can be played offline, but interaction with the Atlas requires online connectivity.
The player must assure the survival of the Traveller, as many planets have dangerous atmospheres such as extreme temperatures, toxic gases, and dangerous storms. Though the player can seek shelter at alien bases or caves, these environments will wear away at the exosuit’s shielding and armour and can kill the Traveller, thus the player must collect resources necessary for survival. By collecting blueprints, the player can use resources to craft upgrades to their exosuit, multitool, and spacecraft to make survival easier, with several of these upgrades working in synergistic manners to improve the survivability and capabilities of the Traveller. Each of these elements have a limited number of slots for both upgrades and resource space, requiring the player to manage their inventories and feature sets, though the player can either gain new slots for the exosuit or purchase new ships and multitools with more slots. Many features of the exosuit, multitool, and spacecraft need to be refuelled after prolonged use, using collected resources as a fuel source. Better equipment, and the blueprints and resources to craft that equipment, are generally located closer to the centre of the galaxy, providing a driver for the player.
While on a planet, the Traveller may be attacked by hostile creatures. They also may be attacked by Sentinels, a self-replicating robot force that patrols the planets and takes action against those that take the planet’s resources. The player can fend these off using the weapons installed on the multitool. The game uses a “wanted level” similar to that of the Grand Theft Auto series; low wanted levels may cause small drones to appear which may be easily fought off, while giant walking machines can assault the player at higher wanted levels. While in space, the Traveller may be attacked by pirates seeking their ship’s cargo, or by alien factions with whom they have a poor reputation. Here, the player can use the ship’s weapon systems to engage in these battles. Should the Traveller die on a planet, they will be respawned at their last save point without their exosuit’s inventory; the player can recover these materials if the player can reach the last death location. If the Traveller dies in space, they will similarly respawn at the local system’s space station, but having lost all the goods aboard their ship. Again, these goods can be recovered by travelling to the point at which the player died in space, but with the added uncertainty of pirates claiming the goods first.
Each star system has a space station where the Traveller can trade resources, multitools, and ships, and interact with one or more aliens from three different races that populate the galaxy. The player may also find active or abandoned alien bases on planets that offer similar functions. Each alien race has their own language, presented as a word-for-word substitution which initially will be nonsense to the player. By frequent communications with that race, as well as finding monoliths scattered on planets that act as Rosetta stones, the player can better understand these languages and perform proper actions when interacting with the alien non-player characters, gaining favour from the alien and its race for future trading and combat. Consequentially, improper responses to aliens may cause them to dislike the Traveller, and their space-bound fleets may attack the Traveller on sight. The game includes a free market galactic store accessible at space stations or alien bases, where some resources and goods have higher values in some systems compared to others, enabling the player to profit on resource gathering and subsequent trade.
No Man’s Sky is primarily designed as a single-player game, though discoveries can be shared to all players via the Steam Workshop, and friends can track each other on the game’s galactic map. Hello Games’ Sean Murray stated that one might spend about forty hours of game-time to reach the centre of the galaxy if they did not perform any side activities, but he also fully anticipated that players would play the game in a manner that suits them, such as having those that might try to catalogue the flora and fauna in the universe, while others may attempt to set up trade routes between planets. Players can track friends on the galactic map and the system maps. Due to limited multiplayer aspects, Sony does not require PlayStation 4 users to have a PlayStation Plus subscription to play the game online.