Anyone here heard of it? SEGA made the first edition back in about 2000, but it's been updated and republished on the DC, PC, GC, XBox, and then PC again, the last one being Blue Burst.
Personally, I think it's the last good game SEGA have made and ever will, and damn, is it good. <3
I couldn't possibly explain the gameplay, because it's so clean and straightforward (except the horrible targetting system) and dangerously addictive. You'd probably be best looking up videos on youtube. Actually, you should look up the soundtrack, too. <3