A small group of interested upper secondary education students participated in a workshop where they created a particle-based physics engine and used the engine to implement a hanging cloth simulation and a two-dimensional heat diffusion model of their own creation. During the implementation of their models, learning opportunities present themselves in the form of opening up and exploring different dimensions of variation for the students. By varying aspects and discerning how these changes affect the program, students can construct meaning about the system. The students were video and audio recorded during the workshop and interviewed afterwards. Based on the transcripts, students use of programming was analyzed using social semiotics and variation theory of learning with a focus on the three aspects: coding, visualization, and interaction. The analysis identifies usages of programming such as a transductive link between semiotic systems, the ease of varying and iterating aspects, and the ability to enter into a loop of discovery and understanding.