Cataclysm: Dark Days Ahead (aka Cataclysm DDA or CataDDA) is an open source survival horror roguelike set in a post-apocalyptic and fictional New England.

Unlike most roguelikes, it has no goal: the player is free to explore the procedurally generated map, clear areas of monsters, work with NPCs, and build shelters and vehicles. The gameplay is mainly based on day-to-day survival, and the game tracks parameters like hunger, thirst, morale, illness and temperature which the player must manage to stay alive. Like most roguelikes Cataclysm: DDA follows turn based gameplay.

The world has support for seasons and dynamic weather conditions and the season lengths can be modified during world generation. A typical world has cities, towns, rivers, forests, bridges and other landmarks. Cities and towns generally have all the common establishments generally found in real world such as houses, departmental stores, malls, parking lots, swimming pools, hospitals, malls, etc. Exotic locations such as Science Labs, Military installations, missile silos can be found in remote places throughout the whole world. Latest versions have support for experimental 3-D buildings.

You emerge from the shelter into the dim light of an overcast day, and look around for the first time since the disaster.

The world as you knew it is gone and in its place, a twisted mockery of all that was once familiar.

Everything was cast aside in that frantic race for the shelter. You have no food, nothing to drink, no weapons. Nothing but your ingenuity and the fierce determination to survive against appalling odds.

A grim prospect faces you. Perhaps worse even than the nightmares of last night, when you were tortured by dreams of the dead themselves rising to jealously tear life from the living.

You cast your eyes up the road and begin to walk towards a house in the far distance. Things may be bad right now, but you've got a sinking feeling that there are darker days ahead.