Needs better shoot animation. Needs some sounds.
Game play needs speeding up - make fast forward the normal speed.
Seem to be missing the graphics for the minigun.
I eventually died on a level where I needed 2 AA guns - as my 1 fully upgraded one wasn't able to cope - but had handled the previous air level fine. Needs a bit of warning.
Nice start, but incomplete. Doesn't tell you when the mission is complete, doesn't give enough info to identify the target, values on front panel are just place holder.
Controls are awkward - to much shifting between mouse and keyboard. Needs a better way of selecting ammo. Needs a longer music loop. I always seem to start pointing the wrong way. Some of the upgrades are just silly.
Really, really needs the ability to switch to fighting the next available target in melee once you've killed the one you were fighting. Having him just stand there getting chopped to bits is so annoying.
Shots don't last long enough for proper ballistic shooting (off the top of the screen and back down on a vertical angle). Shouldn't be to had to provide some AI that'll make 1 player an option. (Just work out (or hard code) a good angle and add varying amounts of random variation).