Quantum

Quantum was a color vector arcade game designed by Atari Inc. in 1982.

Gameplay
The premise of the game was related loosely to quantum physics in that the player directed a probe with a trackball to completely circle atomic "particles" for points, without touching various other particles. Once the particles were surrounded by the probes' tail they were destroyed.

Entering one's initials for the game's high score table was unique compared to all other games of the era; the player would use the trackball to circle the letters of his or her initials in the same fashion that was used to circle the particles during gameplay. If the player achieved the highest score on the table, the initials screen was preceded by another in which the player would use the trackball to actually draw his or her initials in an entry box. Some players were adept enough with the trackball to actually write their names legibly in the box.

The Particles

 * Electrons: 20 points - Rotated slowly around the nucleus
 * Nuclei: 300 points - Moved slowly around, bouncing off walls. Would clip the probe's tail if it crossed it. Capturing all the nuclei on the screen advanced play to the next level.
 * Photons: 200 points - Entered from one edge of the screen, span across the screen, and disappeared off the other side.
 * Pulsar: 400 points - Travelled towards the probe, pulsing its "arms" in and out as it moved.
 * Positrons: 200 points - Formed by stray electrons left when a nucleus exploded. Moved from its point of origin to the edge of the screen very quickly.
 * Splitters: 100 points - Travelled in a random pattern across the screen, flashed colors and split into 3 after a few seconds, each of these 3 splitting again after a few more seconds.
 * Triphons: 100 points - Moved around the screen randomly.

Trivia

 * This was one of two games designed for Atari by General Computer Corp. (the other being Food Fight) as a result of a legal settlement between Atari and GCC. The production run for this game is rumored to have been around 500. The game did poorly in the arcades and rumor has it that some disgruntled operators returned the game to Atari. Many unsold/returned units were sold to the public and Atari employees.