Oh, man. One of my all-time favorite games finally made it to classicdosgames.com. Hard as hell, but addictive like crack (especially fun with two players, although the computer helper AI isn't too bad). I wasn't aware there was a shareware version.
Also, I think this was originally a Commodore Amiga game (which is how I played it first), which later got ported to the Genesis/SNES and DOS.
I heard stories a few years back this was going to get ported to the GBA, along with 'Speedball II' (which is another great classic). The
press release is still on the Bitmap Brothers' site. Unfortunately, it never released (to my knowledge), although 'Speedball' did.