If you roll a ball forward, it will keep rolling that way until it’s stopped by an obstacle (or slowed by air resistance and friction).
This is an example of Newton’s First Law of Motion: objects at rest stay at rest, and objects in motion stay in motion with the same speed and direction unless acted upon by an unbalanced force.
Rockets are no exception to this rule. If we shoot a rocket into space, it will move in a straight line (and will keep on moving!) until an outside force stops it or changes its direction.
In this game, students become rockets and move through space according to Newton’s first law of motion.