Thank you for playing! The cursor keeps moving to challenge players who want to place barriers in precise locations. You can press the down key at any moment to stop the continuous movement. You place the beam to claim space on the line, and it acts as a barrier to the moving dots, who cannot enter any claimed space. Every time you press the spacebar it places a single beam (barrier) on the line, *but* if that beam clears a bigger area on the level, it automatically fills that cleared area with other spaces, to let you know that all that space is now claimed and no action can happen there. Whenever you claim 51% of the line, the line clears and you move to the next level :)
Hopefully that clears it up! Let me know if you have any other question, comments or suggestions \o/