Spheres of Chaos is quite simple to play.
The small grey arrow in the centre of the screen is your ship, floating in space.
You aim it by using the left joypad mushroom, or by moving the mouse left and right. One joypad / mouse button fires it's engine, longer presses make it go faster.
The ship drifts in whichever direction it is going, and gradually slows down by friction. To stop it faster, turn around and use the engine again. Or, press a joypad button (different one, experiment to find which), or middle mouse button, or left-alt, which increases the friction (quite usefull against black holes).
There are other things floating about in space with you. Just some harmless polyhedra at first, but it doesn't stay that way for long. Press a joypad button, or left mouse button to shoot them, and make some nice explosions.
The aliens all behave differenly. Some chase you, some chase each other, and some do their own thing. Some have more friction and stick to black holes, some just drift. Most split into several parts when shot.
Press another joypad button, or quickly push the mouse upwards, to hyperspace and escape an imminent crash (that's 4 control buttons so far). You will land somewhere randomly, often on top of something else. Bad luck.
Sometimes when you shoot something, a spinning triangle will appear. If you run into it, your ship will get an extra ability for a short time. Three way shots, shields, or a smart bomb, that sort of thing.
The triangles slowly change colour, and the colour determines the ability it gives. If you shoot them they also change colour, and go bongggg.
Sometimes when you have cleared a level, a large boss alien appears. These take a lot of shots to destroy, and have more complicated behaviour. When you destroy them they create several triangles. The demo has one at the end, and the full version several more types.
At random intervals, one or several 'black holes' will appear. These have gravity that attracts or repels the other aliens and shots. The gravity is stronger closer to them, and you can 'orbit' them if you are carefull. The also spray colour particles around and look quite pretty.
If you are slow in clearing a level, small unfriendly ships start to appear. First one at a time, then in swarms, a bit like wasps.
Occasionally other strange objects will appear. Fields of flowers, things that are supposed to be a bit like bacteria, noisy bomb dropping things, spinning shooty things.
As the game progresses it gradually gets faster, there are more things on screen, new aliens appear, and it generally gets more manic. Scoring points earns extra ships, every 10,000 points at first, but less often the futher you go (otherwise it just becomes very easy because of the amount of scoreable stuff).
The registered version allows multiple players, with a variety of game variations.