Multi-digit subtraction is a central part of Grade 1–3 mathematics that many students struggle with and is challenging to teach. We used design research to investigate how and to what extent game-based activities could support Grade 1 students’ development of methods for two-digit subtraction. Our results show that a short sequence of activities based in the game led to 85 % of students being able to document at least one method for two-digit subtraction, and 42 % being able to document at least two different methods. However, the way the teacher picked up students’ methods for discussion and how the teacher documented them affected what methods students developed.