This article explores the features of students' reasoning and sense-making when computer programming and mathematics interact, specifically, using the exterior angle concept to make different regular polygons with Scratch as a programming tool. At the end of the 2019 spring term in a public elementary school, data were obtained from a pretest, a posttest, programming tasks, surveys, audio recordings, and research field notes. Fifty-six students aged 13-14 years participated in the study. Concepts from variation theory in combination with a post-structuralist philosophical perspective were used to analyse what features of tasks allow students to experience reasoning and sense-making and what features are discerned in students' reasoning and sense-making. The results illustrate the features of tasks as well as how connections are created during task construction between different concepts from mathematics and programming to promote sense-making and reasoning. The results also indicate that the features discerned in students' reasoning and sense-making consist of a flow of lines that are diverse in form and are distributed across the task assemblage. The use of repetition as difference at the level of idea is powerful in order to create a close connection between reasoning and sense-making and to support differences and heterogeneities.