"X" switches boxes that are in your vision on and off (green and red, respectively). They move every 3 turns outside of your vision in the direction of the arrow. I wrote "objects" in the tutorial because I didn't know if I was going to add more interactive elements, but I didn't have time.
You probably didn't get it because I didn't add any animations or sounds that would make it clear they're moving. I'll make the tutorial better next time so that more people can understand the game. Thanks for the feedback!