In this paper, we discuss the need for new approaches to research regarding coding to support students in developing practices in computational thinking, such as abstraction and decomposition, in multidisciplinary contexts. We explore students' activities with a tool integrating constructionist textual programming activity with game-based learning and specifically game modding. In this context, we designed a programmable 'design-to-play' game developed with the computational environment MaLT2. MaLT2 offers the affordances of textual programming, dynamic manipulation, and 3D navigation for the design of 3D animated models aiming to give children access to, otherwise, complex, computational and mathematical ideas. To develop an understanding of children's learning activity regarding computational practices, we organised an empirical study with middle-school students, who played a game called 'Code-the-Mime'. It is a charades-based game in which the players manipulate, programme, and modify a digital human model to describe a word to their teammates. The preliminary findings indicate that the affordances of MaLT2 in conjunction with the game context enabled students to express and develop key computational practices, including decomposition, pattern recognition, analysis and abstraction, in a meaningful and multidisciplinary context.