Grab the mouse with one hand and put your fingers of the other on the [arrow] or [WASD] keys. Click the mouse to fire.
Each level presents you with an increasing number of pods, round bumper-like objects that tend to gravitate towards your ship, and a string-creature that is rather hypnotizing to watch. String creatures require hits perpendicular to its line segments, so you will have to keep moving to clear each level. You will also need to protect your orbiting shield ring, or it's eternal darkness for you.
Fortunately, you have an Intergalactic Hyperspace Pulse weapon available to you by pressing the [space] bar. But it requires recharging after use. There are also a few power-ups that can help you along the way: orange shield boosts, orange [P] firing rate increasers, hyperspace pulse boosters.
And while there isn't much more than that to this cute little game, the gameplay kept me going at it for a long while. Did I mention it's terribly addictive? Great old-school arcade fun in a tight little package.
Cheers to Dann for the link!