Dots. Lots and lots of dots.
Circles: the idea here is to practice your PK skills by getting the circles to describe a larger circle. The all start out in a clump in the middle, and move around at random.
Circle Game: Ever want to practice microPK? Here's a quick and simple game to do exactly that. A bunch of circles are set on a plain background, and a simple java script thing sets them to moving about in a pseudo-random manner. Your task? Get them to co-operate to form a larger circle of dots on the field of play... exact size is up to you. "Fast" has more jitter in addition to more speed.
Basic Circle Game: An easier PK game, this is one of the 'push in one direction or the other' exercises. Circles drop from across the top of the field of play in a pseudo-random fashion. If they hit the left side or the left half of the bottom of the field of play, the score goes up. If they hit the right side or the right half of the bottom, the score goes down. Choose a side, and push the dots over there. The object of the game is to get a score as far from zero as possible, in either direction.
Circles: Yet another PK game with circles. Someone requested a version in which the dots are generated (pseudo-) randomly, so here it is. Same basic idea: arrange the dots in a circle. You might be detecting a pattern here...