Stolen from SA's forums.
Fraxy is basically a homegrown 360 degree type of shump. Neat by itself, but here's the cool part:
You design the bosses. It comes with an editor.
http://mokeron.hp.infoseek.co.jp/zg/fraxy_main.htmlYou want the files listed at the top. The one with "eng" in it is all the pre-made boss files in english, so extract those (remember to turn off that "use folders" option in WinRAR/Winzip) and overwrite the ones in the /enemy/ folder of the main game.
The editor is pretty easy to get into. Some of it is a bit arcane to me (lot of odd options for frames and animation-cycle stuff you can play with, and no documentation I can read).
The game itself is simple.
You move with the arrow keys, you direct your fire with the mouse, fire is left mouse button, right click for "boost" which makes you move faster (click quickly to go faster), mouse-wheel changes weapons. I believe you can enable more weapons, but I dunno how.