There is a solid foundation of a game here but there is also a lot to improve. I appreciate the inclusion of the Halo assault rifle by the way. But the concept, gunplay and graphics of the game are pretty nice. The biggest thing holding this game back is level design:
It feels largely like the levels were cobbled together without concern for if the way things are presented actually makes sense. There is no purpose to many rooms, buildings feel labyrinth like and the placement of explosive barrels is rather haphazard and makes no logical sense.
I feel like if more time was put into making the levels feel coherent as a whole and like each campaign mission is a continuation of the one before the game would feel a lot more complete and interesting.