Retro Tanks is a 4 player local co-op tank skirmish game with plenty of features, such as game customisation, multiple weapons and upgrades, team-play mode, 3 vs 1 mode, single player time-attack mode, post game statistics and ribbon awards, medal system (achievements) which unlocks further game content, tank build-tester and plenty more. There's around 50 levels at present which are played in either campaign mode or free level select. The campaigns are 10 levels long and dedicated to specific set-ups, e.g. team-play campaign for 2 vs 2 games with each level carefully designed to create a tight co-op battle arena.
If you would like to test out Retro Tanks, please feel free - I'd appreciate any comments as well.
The forum can be found at the following link: Xboxforums.create.msdn.com
If you have any questions regarding how things work then please shout, although it should all be pretty straightforward and covered in the game.