Space space space. Sick of it yet? Of course you're not. Here's some more!
I'm fully counting this as space because you defend yourself against UFOs, and UFOs are totally from space. In fact, if we wanted we could count anything as being about space! We're entirely floating in it right now. Anyway, the point would be, Pondwater's The Ancients' Tome is an excellent freebie indie game that you should absolutely be playing. If you're not running Vista. It no worky there.
The game is controlled through three rows of three keys, either QWE and down, or the numpad, with each key corresponding to an icon in your central floaty, er, thing. Combine the icons in the correct patterns and, er, stuff happens. Like staying afloat, or creating defences, or fixing your vessel's damage. But because the icons move around, and because you're quickly being asked to carry out very many tasks at once, your fingers are quickly a blur on the keys as you attempt to keep up with the demands. I found myself inwardly chanting, "Man, star, platform; man, star, platform; FIRE FIRE! FIRE FIRE!; face, bolt-thing," and so on. As you progress, you reveal peculiar letters telling the story. As well you should. Thanks to roBurky for the top tip.