I put it as (3D) cause the 3DS version is the newest one, but other than visual style it's the same game. I have the 3DS and Wiiware versions. Sadly 3D doesn't have Boss Rush and Curly Brace modes, but both are great and the new style is nice too. The music is the same cool 8-bit retro style in both games.
For those who have never seen/heard of it, it's a metroid style game that was originally made by one person and was a pc indie game. It has a small bit of rpgness as you can lvl weapons up a bit but taking too much damage will lvl em down also. The action is pretty quick and keeps you on your toes pretty well. I haven't beaten it yet but that was what I was hoping to do with the 3DS one, heh.