Development of digital resources is difficult due to their particular complexity relying on pedagogical aspects. Another aspect is the lack of well-defined development processes, experiences documented, and standard methodologies to guide and organize game development. Added to this, there is no documented technique to ensure correct implementation of a competency in a videogame. This research proposes a Short Serious Game Development Process founded in Software Engineering paradigms and complemented by previous efforts on large scale development of digital learning resources. This paper focuses in a technique called Competency-Based Decomposition that achieves implementing a formal competency into a short serious game, with which the formal learning process will be complemented to improve the way students learn. Through a case study will be demonstrated its utility by implementing the process and the technique in the whole of mathematics competencies for sixth grade of elementary school in Mexico. The result of applying the proposed process for study case is a collection of video games that satisfactorily implements the competencies and its contents, its expected learning and its knowledge areas specified for sixth grade of elementary school in Mexico by the Ministry of Public Education.