Okay, so you're trapped in yet another nuclear reactor (see Reactor). But this time, you have to capture particles without crashing into them. Using a trackball as your only controller, you zip a cursor around the screen which leaves a line trailing behind it. If you can use the line to close a loop around the particles that are bouncing all over the place, you'll capture them and they'll disappear. Capture them all, and you move onto the next, and more difficult level.

The trick is that some particles will throw up barriers in your way that you have to avoid. Others will start reproducing unless captured right away. Still others will fly straight at you - so you have to keep moving. Also, if you don't capture something, your cursor will increase in size - making you a bigger and bigger target.

Quantum is a great mix: an action game that requires a lot of patience. You have to have quick reflexes to react to an opportunity to capture particles, but you have to bide your time and wait for an opening. If you move recklessly, you're going to find yourself just crashing into things. The trackball is the perfect controller for this game, since it allows for both finesse and quick, sweeping action.

Head-to-head play. Do this: play Quantum. Then, play it again, and imagine playing against someone at the same time. He's trying to capture you, you're trying to capture him, you're both trying to capture particles, and you're doing all this while avoiding collisions and each other. Who knows... Quantum could have been up there with Joust and Atari Football as one of the great head-to-head games of all time.