Gravitas has been released!

Gravitas
Gravitas is now available on the Xbox Live Marketplace for 80 MS points.

An artillery game, somewhat akin to scorched earth, but in 2D, set in space and featuring different planets with gravity you have to slingshot your shots around. Primarily a multiplayer game supporting four local players it’s excellent for parties and an absolute bargain for $1.

Although I may have a slightly biased opinion.