This paper presents the XML-based Video Game Description Language (XVGDL), a new language for specifying Video games which is based on the Extensible Markup Language (XML). The proposal is portable and extensible, and allows games to not only be defined at engine level but also includes specific features that can lead the game design process whilst simultaneously reducing the gap between game specification and its corresponding game implementation. XVGDL is as generic as possible, making it possible to describe different genres of games. This paper focuses on presenting the basis of the language. The paper describes the syntax as well as the components of XVGDL, and provides examples of their use. Defining games via XML structures provides all the advantages of the management of XML files and opens up interesting lines of research. Our proposal provides a number of novel features. So, XVGDL game definitions can be managed as any other XML file, which means that it can be automatically handled by any XML file management software. Another interesting feature is that XVGDL can specify game components (e.g., game Artificial), in-game processes (e.g., the procedural generation of maps) or in-game events (e.g., the checking of the conditions to end a game match) via the association with external (possibly non-XML) files. Moreover, XVGDL files can be easily validated as any XML file what means that validations against a particular Document Type Definition (DTD) or XML Schema Definition (XSD) are possible. In addition, the paper presents a first prototype implementation of a (text-based) interpreter that allows XVGDL game specifications as a playable game to be executed. This tool not only validates our proposal but also represents a first step towards smoothing the path to obtaining an executable version of a game from its game specification.