Costello is an educational MUD — a text-based online role-playing game

Role-playing game

A role-playing game is a game in which players assume the roles of characters in a fictional setting. Players take responsibility for acting out these roles within a narrative, either through literal acting, or through a process of structured decision-making or character development...

 — designed for teaching English as a foreign or second language. It is offered online as a free service. Created in 1995, it was innovative in its use of the MUD

MUD

A MUD , pronounced , is a multiplayer real-time virtual world, with the term usually referring to text-based instances of these. MUDs combine elements of role-playing games, hack and slash, player versus player, interactive fiction, and online chat...

 medium for EFL/ESL instruction,and has received positive critical response.

Characteristics

Costello is intended to function both as an engaging game and a teaching environment, following the reasoning that players will be more motivated to learn if their skill acquisition aids them in their game-play. To avoid degrading the value of language skills acquired, the game's command parser avoids support for ungrammatical shorthand forms; where a typical MUD might allow a player to examine a hat with the syntax l hat, Costello requires look at the hat. An integrated dictionary provides explication of unfamiliar terms.

The game may be played through a Web browser using a Java applet or using a Java client distributed on a CD-ROM with the course textbook. A non-networked standalone application version of Costello is also included on the CD-ROM.

Costellos tagline is "Quest-Based Learning", reflecting its structuring of learning experiences through quests

Quest (gaming)

A quest in role-playing video games — including massively multiplayer online role-playing games and their predecessors, MUDs — is a task that a player-controlled character or group of characters may complete in order to gain a reward...

. An earlier tagline was "English Through Imagination".

Technical infrastructure

Costello runs on the MudOS

MudOS

MudOS is a major family of LPMud server software, implementing its own variant of the LPC programming language. It first came into being on February 18, 1992. It pioneered important technical innovations in MUDs, including the network socket support that made InterMUD communications possible and...

 game driver and a version of the Ain Soph Mudlib from Lost Souls

Lost Souls (online game)

Lost Souls is a MUD, a text-based online role-playing game set in a medieval fantasy world. It has an extensive history of technical innovation in its field and has received critical praise....

, with customizations engineered by former Lost Souls developer Jason "Rand" Hitt and others.