After pressing the green flag, click on Start Game. Move the rocket up and down with the up and down arrow keys. Avoid the asteroids. The game will end and your scores will be totaled after 30 seconds
The game creates a list of each movement you make and every time you hit an asteroid and then at the end of the game a code scans through the list and each time it finds a certain movement it +1s the corresponding variable. I have a separate list collecting data and counting each time the game has been played.