potential..
Lots of potential, EXCEPT...
1: maybe each weapon tier (shot gun, normal, scatter) can have its own row, to make upgrades easier
2: mission 18 has a glitch, it only lets you take 9 shots, and calls you a failure on the 10th even if you do hit.
3: the shotgun is WAY to inaccurate. its just stupid..
4: mission 19 is dumb. its not skill, just luck because of how inaccurate the shotgun is.
Fix these, and you'll be well on your way to a very very good game.