Dwarf Fortress is a sandbox game created by Tarn Adams of Bay 12 Games.

The graphics are ASCII with various tilesets available.
In Fortress Mode, the player helps their dwarves survive by declaring
areas to collect food, create workshops, create defenses, etc.
In Adventure Mode, the player takes the role of an individual who can
explore the world (including their own previously created forts).

https://dwarffortresswiki.org
https://dffd.bay12games.com

Note: A local copy of the game will be placed in ~/.dwarffortress when
run, where tilesets/graphics and config files can be changed.
An original copy of the program is kept in /opt.
After an update, delete your local .dwarffortress folder before running.
(Regions kept in data/save can be reused for minor version updates.)