There's not enough good things that can be said about this game.
From the beginning of the campaign its clear even the developers saw their story as superfluous. Levels are a series of traps and enemies all hell bent on destroying you. If you can avoid them you'll rack up higher scores based upon multipliers. Difficulty scales well. On easy it is easy - a cake walk. Normal levels can be challenging at first, but after a few hours playing they too will become easy. On hard, the game is legitimately challenging from beginning to end. You will die, but likely won't find yourself berating the game as "unfair," the usual pitfall of the hard difficulty.
In multiplayer the game shines. The idea of two dimensional shooter sounds shallow and absent minded at first. In theory, one must wonder where player skill is involved. From the first match it should become clear - this game requires skill. A player with good cooridination will immediately find himself with an edge over other players.
Besides the standard death-matches and capture the flag games, Babo Invasion introduced one completely new, innovative gametype. In invasion mode two teams are called upon to create the map they are about to play on; each team creating half. A base, three "shield nodes," and numerous other tiles are all placed in a few short minutes. To win one team must deactivate the others shields and destroy their base. It sounds as if it might be over complicated, but the developers executed the gametype well; the result is just plain fun.