Not bad, especially for your first platformer. But, there are a few flaws with it. First off, the enemies that shoot at you shoot at random times when you can see them, so it's impossible to know when to avoid them. Next, there is no real threat. The enemies are stationary, and all have the same weapon. Third, the enemy spawning when you do get the briefcase is always outside he building, and, again, they can't move, they all have the same weapons, and they are often clustered into groups.