It is a GEM. Arcade mode is about playing only one level for high scores. The 3D cells on the 3DS version do look nice in 3D, but after the lovely HD visuals on the WiiU, it is a little bit of a comedown. I believe the shooting is controlled, on the 3DS without the CPP, with the A B X Y buttons, which would be like the old Geometry Wars DS' second control scheme.
I can't seem to top the high score charts on the single player, but on 2 player mode my 6 year old son and I rule the boards, on Epsilon and Zeta. Try it out, 2 player is fun, and if your partner is shite, they can steal your extra lives to continue.