Kept me playing for a bit buuuttt...
I noticed a few bugs. In the campain mode, at least on the first level, one of the CPU players got a headshot on his own teammate, seemingly on purpose. And secondly, the challange mode won't let me throw a grenade up and to the left. If you try and turn your angle up, it automatically turns you around.
Other than that, not a horrible game. Could use some improvemennts though, like more weapons.