Cataclysm: Dark Days Ahead

Map view showing a large city

The world can be persistent between games. When starting a new character after the death of a previous character, the new game can be set in the same game world as the last.[17] The world has support for seasons and dynamic weather conditions, and the season lengths can be modified during world generation. Recent weather conditions/events added include the portal storms, which were initially only mentioned in the main storyline for CDDA, during these portal storms, nether monsters will appear and can cause negative effects on the player when they get caught outdoors during the storm if not outright kill them, but during the portal storms, a dungeon will appear, this dungeon can grant the player unique temporary status effects or items by travelling through it successfully.

A typical CDDA world has cities, towns, rivers, forests, bridges and other landmarks. Cities and towns generally have several common establishments often found in the real world such as houses, stores, malls, parking lots, swimming pools, hospitals, and more, but hold danger in the form of large hordes. Rarer locations such as labs, military bases, and missile silos can be found in remote places throughout the world. Latest versions have support for three-dimensional buildings.[18]

While most of the action in CDDA is liable to happen on the surface overworld, as traditional with roguelikes, the world does contain underground dungeons. Examples of these include mines, labs, and strange temples.

Player creation menu which shows Profession, Traits, Skills and Stats

Characters can be generated randomly or can be custom-built to suit player gameplay and preferences. Players choose from several available initial scenarios. The default scenario is "Evacuee" in which the player starts from an evacuation center with few provisions. Choosing harder scenarios awards the player with points with which they can create more powerful characters.

Like most roguelikes, the game allows players to initially choose from various professions and each profession has its own set of traits and skills. In character creation, positive traits can be chosen by consuming points, and stats like strength and intelligence and skills like archery can also be increased through spending points. Negative traits earn the player more points to spend on positive traits, stats or skills. Traits that have a greater impact on gameplay have more points associated with them, ranging from minor traits like "Tough Feet" and "Clumsy" to game-changing traits like "Night Vision" or "Kaluptic Psychosis", which causes hallucinations, and even "Nyctophobia", which hinders the ability to enter dark areas and causes bad effects if caught out in darkness. Characters can increase their skills gradually once in-game by practicing the respective skills or reading books obtained from various sources found within the cities or towns, or degrade over time with disuse if the optional skill rust system is enabled.

The game has a menu which shows the character's current conditions such as hunger, thirst, morale and illness. In order to survive, the character has to consume food and water often, and sleep on a regular basis. If afflicted with an illness, the player must use certain medications in order to treat the diseases, most diseases can recover their own, but some others can only be removed with the right medication, or vice versa. The menu also displays the character's stats.

Crafting menu

Unlike most roguelikes, CDDA focuses heavily on crafting, with many basic necessities such as clothing and food being craftable from raw items that are found lying around the world. For crafting to be successful the player needs the necessary raw materials and equipment. The player also needs to learn the recipe of the object to be crafted, which can be unlocked by reading books from libraries. Successful crafting leads to an increase of the corresponding skill. Craftable items are classified into Weapons, Ammo, Food, Chemicals, Armor and Other, with several subcategories in each of them.

Crafting can be hampered by player conditions such as low morale or other external game conditions like insufficient light or the presence of monsters nearby.

Vehicle construction and repair menu

CDDA features an intricate construction menu where one can perform activities ranging from simple construction, like boarding up a window or digging a pit, to elaborate ones like building a reinforced concrete wall, digging a well or creating basements. Like crafting, construction requires raw materials like brick, stones, or nails. Equipment required for construction can be either salvaged from cities or can be crafted via the crafting menu from additional raw materials. For the most part, the terrain in the game is fully destructible, meaning that the player and other entities can destroy it or build structures on it.

Vehicles can be repaired or even built from scratch using the construction menu. Players are reported to have created vehicles of quite different sizes and capabilities, from small quad bikes with limited storage[19] to huge "deathmobiles"[20] with multiple engines, turrets, machine guns, and chemical labs.

The player can farm land and grow grains, vegetables, berries and other shrubs (e.g. cotton), provided that they find the respective seeds. The final crop can be laid up for later use (though some food may perish), it can be eaten raw or can be used to prepare more elaborate products (e.g. cooking oil, flour, spirits, vinegar, sealed food).

The farming season usually extends from late spring to early autumn and depends on external temperature. Every plant type has different growing rates and growth can be accelerated using commercial or home-made fertilizers. Final output depends on the character's survival skill: the higher the skill, the higher the yield of every single plant. Once harvested, all plants are considered "dead" and leave straw (grains) or withered plants and some seeds.

There are a plethora of monsters and creatures found in the world. The wilderness contains many animals, ranging from small passive animals such as squirrels, rabbits, and rats, to large aggressive predators and sometimes hostile herbivores ranging from moose to wolves and bears. These animals can be hunted for their meat, fur, bones, and organs for cooking and sometimes chemistry.

The main threats to the characters are the zombies controlled by The Blob that roam mainly the cities and some areas within the wilderness. Zombies come in many shapes, abilities and sizes, and most (but not all of them) are infamous for their ability to revive for some time if they are not butchered or smashed to a pulp. The game also features a wide range of adversaries ranging from mutant humans and animals to aliens and interdimensional creatures, often inspired by the works of H. P. Lovecraft and other popular horror and science fiction genres.

As the days go on, many zombies and creatures will mutate into more powerful forms, progressively increasing difficulty. Mundane animals may be replaced with zombie or mutant versions, further reducing access to edible meat while making the world more hostile.

Despite the increasing deadliness of zombies and monsters, unlike most other games, the number of zombies and monsters in a given area (not counting the overall infinite world) is limited, when the zombies and monsters of an area are dead and rendered unable to revive, they will no longer spawn in that area.