This paper describes a study into how secondary school students construct knowledge of programming. The study consists of three classroom sessions. In the first session the students play a simple video game called LumberJack. Then, they are asked to describe the rules of they themselves playing the game as an algorithm in natural language. In the second session, the students are asked to design an automata for a program that plays the game. In the third and final session, the students write programs that play the game and execute them in the programming language called TurtleBots.