Text based adventure games or interactive-fiction could range in complexity from a simple multiple-choice system that allows a player to pick which part of a story to visit next to a complex RPG-style game with a persistent, dynamic game world in which the player can interact with items, NPCs (non-player charaters) and possibly other players.

In the game world there may be multiple rooms, each with a name and description. Rooms may contain doors or paths to other rooms in the game world. Rooms may contain zero or more items, some of which can be picked up by the player, others which can not.

In a more complex game the player may have an inventory of items that can be collected from the game world. The player may also have stats (e.g. vitality, strength, charisma) that are updated after certain events, such as winning in combat or solving a puzzle. In turn, the value of stats could affect the player’s likelihood of succeeding in future combat scenarios, finding items, opening locked doors, etc.

Game Engine

A game engine that can drive such a game will have to handle a few tasks:

1. Read a representation of the game world from a file or files stored on disk. The files must be stored and formatted in a way that the game engine can understand.

2. Maintain in-memory data structures representing the state of the game world and player.

3. Read commands from the player, some examples of player commands might be

   > walk north
   > look around
   > pickup candlestick
   > fight monster
   

   commands will have to be parsed, checked for correct syntax and translated into in-memory structures.

4. Update the in-memory structures associated with the game world based on in-memory structure(s) parsed from player commands.

5. If a “save game” feature is desired, the engine will need the ability to translate the in-memory structure representing the state of the game into a Data File Metaformat that can be stored as a file on disk.

Game Interface

The user interface of a text-based adventure game should be able to

1. Display information about the current state of the game environment to the player (e.g. description of current room, list of available items, etc). This means it will need to be able to interact with the game engine which maintains the data structures containing this information.

2. Prompt the user for commands, send command strings to the game engine and display any errors that prevented the engine from understanding a command.