The complexity of the game is not too hard and too easy either. You just need to have quick reactions and a bit of luck when opening the presents. I find the shotgun the most useful because of it's burst range which can hit multiple enemies. Though on earlier levels I just use the boomerang (if I find one) then just ricochet them through the vast amount of the enemies. The 'Kingpin' medal is quite hard to get since you need to do at least 3 or more combo for each round in the 'Bowling Mode' to reach 1500+ points.
Overall the game is fun and original. Good work. 9/10