The thesis describes the method of developing an internal domain-specific programming language for the creation of computer games. We present a rough overview of domain-specific languages and their use in the field of computer programming and game development. In the the main part, we demonstrate the basic steps for the development of a simple game engine and then focus our attention on implementing some core language constructs in Ruby programming language that are required for the creation of our domain-specific language. We exhibit the use of the newly-created language by developing a simple Breakout game. Finally, we make a short comparison between the implementation with the domain-specific language and the implementation with a general-purpose language as well as point out some possibilities for further development.